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Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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4
Biological Agents

This chapter provides general information on biological agents, identifies sources of bioaerosols that might be found in aircraft cabins, and summarizes the environmental sampling of biological agents that has been conducted on commercial aircraft. The chapter also describes the two health effects considered most likely to be associated with bioaerosol exposures in aircraft cabins—acute hypersensitivity disease and infectious respiratory disease.

GENERAL INFORMATION ON BIOAEROSOLS

The term bioaerosol includes a variety of airborne particles of biological origin (from plants, microorganisms, or animals). For this review, the committee will consider bioaerosols according to their associated health effects (e.g., aeroallergens, biological toxins, biological irritants, and infectious agents) (see Table 4–1).

Biological Agents in Outdoor Air Near the Ground

Outdoor air up to an altitude of about 1,500m (4,900 ft) contains abundant biological material (Lighthart and Stetzenbach 1994; Lacey and Venette 1995), especially fungal spores and pollen grains. Airborne bacteria and fragments of insects, plants, and soil also are present at various concentrations. Depending on where the plane is located and the ambient conditions (e.g., the time of

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

TABLE 4–1 Examples of Common Biological Agents, Reservoirs, and Health Effects Related to Inhalation Exposure

Agents

Bioaerosol

Reservoirs

Possible Health Effects

Aeroallergens

Plant allergens

Pollen grains, plant fragments

Vegetation, settled dust

Allergic conjunctivitis, rhinitis, sinusitis, asthma

Bacterial antigens

Cells, cell fragments

Growth in water or on organic matter, settled dust

Hypersensitivity pneumonitis

Fungal allergens

Spores, cell fragments

Growth in water or on organic matter, settled dust

Allergic conjunctivitis, rhinitis, sinusitis, asthma

Arthropod allergens

Dust mite or cockroach excreta and body fragments

Settled dust

Allergic conjunctivitis, rhinitis, sinusitis, asthma

Mammalian allergens

Particles of cat, dog, or rodent skin, saliva, or urine

Pets, pests, settled dust

Allergic conjunctivitis, rhinitis, sinusitis, asthma

Toxins and inflammatory agents

Bacterial endotoxin

Gram-negative bacterial cells and cell fragments

Growth in water or on organic matter, settled dust

Humidifier fever, respiratory inflammation

Fungal toxins

Spores, cell fragments

Growth on organic matter

Toxic and irritant effects

Biological irritants and nuisance biological agents

Microbial volatile compounds

Gases and vapors

Bacterial or fungal growth on organic matter

Irritant and nuisance effects (e.g., unpleasant or annoying odors)

Carbon dioxide, body effluents

Gases and vapors

Human breath, body odor

Perception of insufficient fresh air, irritant and nuisance effects

Infectious agents

Infectious viruses

Droplets, droplet nuclei of sputum, saliva, nasal or throat secretions

Infected or colonized persons

Acute viral respiratory disease, influenza, varicella (chickenpox), measles

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Infectious bacteria

Droplets, droplet nuclei of sputum, saliva, nasal or throat secretions

Infected or colonized persons

Diphtheria, pertussis (whooping cough), bacterial pneumonia, meningococcal disease, tuberculosis

Contaminated water

Legionnaires’ disease

Infectious fungi

Spores

Growth in soil or on organic matter

Histoplasmosis, coccidioidomycosis (San Joaquin Valley fever)

Growth in compost or on organic matter

Aspergillus infection

day, ground cover, wind speed, and precipitation), the outdoor air that enters a grounded aircraft through the ventilation system and open doors may contain a mixture of diverse bioaerosols. Exposure of passengers to outdoor bioaerosols in grounded aircraft are likely to be similar to what would be experienced in an airport terminal or in traveling to and from airports (see Chapter 3 for sources of contaminants outside the aircraft).

Biological Agents in Outside Air in Flight

At flight altitude, the air outside an aircraft contains many of the same bioaerosols found at ground level, but at much lower concentrations (Lighthart and Stetzenbach 1994). Therefore, the likelihood of allergic reactions from components of outside air during flight is less. Exposure to solar radiation, the presence of ambient air pollutants, and low air temperature and relative humidity greatly reduce the virulence of infectious agents that may be in outside air at flight altitude (Kim 1994; Muilenberg, 1995; Mohr 1997). Furthermore, the high compression temperatures (about 250° C) and pressure (about 3,000 kPa) of the bleed air used for ventilation are likely to alter allergenic proteins and inactivate microorganisms that still are viable when they enter an aircraft through an outside air intake (Withers and Christopher 2000). Therefore, in flight, biological agents in aircraft cabins arise virtually exclusively from inside sources rather than from the intake of outside air.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

People

People are a primary source of airborne bacteria and are the most important reservoirs of infectious agents on aircraft (Masterton and Green 1991). Studies that have measured the concentration of airborne microorganisms have concluded that culturable bacteria and fungi in aircraft arise principally from the cabin occupants and furnishings. Most microorganisms that have been isolated from occupied spaces, including aircraft cabins, are human-source bacteria shed from exposed skin and scalp and from the nose and mouth. These microorganisms are found normally on the human body (they are normal flora) and only rarely cause infections. People also are indirect sources of some allergens, as discussed in the following subsections.

Arthropods, Pets, and Service Animals

Arthropods

Arthropods (e.g., flies, mosquitoes, spiders, dust mites, and cockroaches) can be found in aircraft, especially aircraft that spend time on the ground in tropical environments. Some of them are of concern because they are considered hazards to public health, agriculture, or native ecosystems, and this has lead to the practice in some countries of disinsection of aircraft (see Chapters 3 and 5). Dust mites and cockroaches are the only arthropods that might habitually infest aircraft and possibly become sources of allergens in the cabin environment.

Dust mites thrive on protein-containing material in dust (e.g., skin scales and fungal spores), especially in warm, humid indoor areas; they can be found in any enclosed space where such conditions exist (Lundblad 1991; Menzies et al. 1993; Hung et al. 1993; Janko et al. 1995; Squillance 1995; Arlian 1999). Dust mites require high humidity because they absorb water vapor through their exoskeleton rather than by drinking water.

Cockroaches repeatedly have been recognized as a common source of indoor allergens (Powell, 1994). They flourish where sufficient food, moisture, and warmth are available (e.g., kitchens, bathrooms, and similar areas), and they can survive low ambient humidity better than dust mites and, unlike mites, search actively for the water they need to survive (Squillace 1995). Allergenic proteins from cockroaches and mites are associated with particles that are 5

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

microns (μm) or greater and become airborne only when settled dust is disturbed (Platts-Mills and Carter 1997).

Pets and Service Animals

Depending on the air carrier, pets that are likely to be carried in the passenger cabins of commercial aircraft include cats and occasionally dogs, birds, rabbits, hamsters, guinea pigs, pot-bellied pigs, ferrets, and tropical fish. Most airlines limit the number of pets allowed in the cabin and the size of the animal carrier. The Air Carrier Access Act (ACAA, 14 CFR 382, Nondiscrimination on the Basis of Disability in Air Travel) protects the rights of air travelers with disabilities and requires that air carriers permit passengers to fly with their service animals in the cabin.

Although pets other than service animals must be confined while onboard and the container stowed under a seat during takeoff and landing, particulate matter, including bioaerosols (particularly allergenic particles), readily can escape animal cages. Of the animals that are permitted to travel in aircraft cabins, cats are of greatest concern (BRE 2001) as they are prolific allergen generators (Chew et al. 1998). Cat allergens exist on skin flakes and saliva particles, a significant proportion of which is small enough to remain suspended in air for long periods (Wood et al. 1993; Ormstad et al. 1995; Custovic et al. 1999b).

Dog allergens (from dander, saliva, and urine) might be carried on the clothing of dog owners or be shed by onboard pets or service dogs. The concentration of airborne canine allergens generally correlates well with the amount in dust, suggesting that dog allergens are carried on fairly large particles that settle quickly (Custovic et al. 1999a,b).

Settled Dust

Settled dust (house dust) is one of the most important reservoirs of indoor allergens and other biological agents, and the allergen content of dust is a primary indicator of exposure to many allergens (Platts-Mills et al. 1992; IOM 1993a; Trudeau and Fernández-Caldas 1994). In aircraft cabins, dust might contain soil particles, fabric fibers, human hairs and skin fragments, residues of cleaning products and pesticides, and particles from arthropods, mammals,

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

and microorganisms. When analyzed by culture, the microbial population in dust is dominated by common spore-forming fungi and bacteria from soil or water (Logan and Turnbull 1999). Although some of the fungi in settled dust carry allergens and some of the bacteria have inflammatory properties, very few of these microorganisms are infectious, or they cause infection only in severely immunosuppressed persons.

Microbiological Growth

Most of the fungi and environmental bacteria in aircraft cabins enter with outside air while aircraft are on the ground or are carried in by the occupants (e.g., on their shoes, clothing, or hand luggage). Infectious agents that are transmitted from person to person generally grow poorly outside the human body, so contamination in an aircraft cabin is unlikely to be a source of them. Although some microorganisms may grow in cabin areas where moisture is routinely present (e.g., in water that condenses on the internal skin of an aircraft and collects in the bilge), exposure of cabin occupants to microorganisms resulting from environmental contamination has not been demonstrated. Furthermore, microbiological growth sufficient to result in bioaerosol release into cabin air would have to be fairly extensive, which is unlikely to go unnoticed on well-maintained aircraft.

Air filters used in ventilation systems collect large numbers of microorganisms and other organic material, but bacteria and fungi that are captured on filters remain dormant and eventually die if water is not supplied (Moritz et al. 1998). If sufficient water is available, fungi can grow and eventually penetrate the filter of a personal respirator (releasing spores on the downstream side of the filter) (Pasanen et al. 1993). Therefore, it is possible that filters in aircraft ventilation systems could be a source of microbes; however, microbial growth on the filters used to clean recirculated air in aircraft has not been reported.

Contaminated Fluids

Several studies have documented that all humidifiers support some microbial growth (Burge et al. 1980; Suda et al. 1995). The predominant contaminants in such reservoirs are waterbome bacteria, often Gram-negative species (which contain endotoxin) and thermophilic actinomycetes (filamentous bacteria that prefer very warm conditions and produce airborne spores).

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Glines (1991) suggested that exposure to Legionella species could be associated with the operation of humidification systems on aircraft. Legionella species were identified in one study of the water in an onboard humidifier and the air in the cockpit served by the humidifier (Danielson and Cooper 1992; Cooper and Danielson 1992). It should be emphasized, however, that the cockpit is humidified on very few aircraft and the cabin air is not humidified on any aircraft (see the section on humidity control in Chapter 2). Therefore, passengers and cabin crews should have no opportunity for exposure to legionellae during air travel. The cockpit crew may be exposed to aerosolized bacteria if the water in a humidifier is contaminated and the unit is one that generates a water mist, but contamination of water used in humidifiers or for drinking is unlikely if the water storage tanks on aircraft are well maintained and the water supply is clean. Furthermore, there is no evidence that Legionella species are transmitted from person to person. Therefore, the risk of disease transmission would be negligible even if a person infected with legionellosis were on an aircraft.

Other Reservoirs of Potential Infectious Agents

Sewage is a potential source of enteric pathogens and other biological agents on aircraft. Shieh et al. (1997) detected enteroviruses in aircraft sewage. Airport waste handlers were identified as potentially at risk for exposure to enteric pathogens in aircraft sewage as a result of contact with waste material. Burton and McCleery (2000) investigated similar concerns for workers who clean, overhaul, and repair aircraft lavatory tanks. Live bacteria were isolated from waste tanks, but none of them were types that are associated with intestinal disease; the authors suggested changes in work practices to reduce inhalation exposures and wound contamination with potentially infectious agents.

Although no studies were identified that directly assess the aerosol-generating potential of sewage-waste disposal systems on aircraft during normal operation or the potential for inhalation exposure of cabin crew or passengers to infectious agents in sewage from aircraft toilets, no significant potential for aerosol release into the cabin and no infections due to the operation of onboard toilets have been reported. Air from the restrooms on aircraft is not recirculated, reducing the opportunity for volatile and particulate contaminants to enter the passenger cabin. Air carrier adherence to regulations related to aircraft sanitation and the practice of good hygiene by passengers should be sufficient

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

to protect cabin crew and passengers from this potential source of exposure to enteric pathogens.

ENVIRONMENTAL SAMPLING ON AIRCRAFT

The 1986 NRC report recommended that the Federal Aviation Administration (FAA) establish a program for the systematic measurement of microbial aerosols on a representative sample of routine commercial flights. In the last 15 years, eight investigations of biological agents in aircraft cabins have sampled a total of more than 200 domestic and international flights on multiple airlines and 17 types of aircraft of various ages and designs (Table 4–2).

Sampling for Culturable Bacteria and Fungi

Bioaerosol samples on commercial aircraft typically have been collected in the breathing zone of a seated person (e.g., with a sampler placed on a tray table); a few air samples have been collected in galleys and lavatories and in supply and exhaust air streams (Wick and Irvine 1995; Dechow 1996; Dechow et al. 1997). Investigators have compared concentrations of biological agents found on aircraft with (1) ground-based public conveyances (Spengler et al. 1997; Dumyahn et al. 2000); (2) common locations in a southwestern city (municipal buses, a busy shopping mall, a sidewalk adjacent to a downtown street, and an airport departure lounge) (Wick and Irvine 1995); (3) hospital guidelines (Dechow 1996; Dechow et al. 1997); (4) a local indoor air-quality standard (Lee et al. 1999, 2000); and (5) an undocumented occupational exposure limit (attributed to National Institute for Occupational Safety and Health (NIOSH) without reference) (ATA 1994; Janczewski 2001). The major observations from the studies, some of which were noted in more than one investigation, are as follows:

  • Concentrations and types of bacteria and fungi on aircraft:

    • Concentrations of culturable bacteria were higher than those of culturable fungi.

    • Bacteria were typical of those shed by humans or were common soil organisms.

    • Fungi were typical of those found in outdoor air and occupied indoor environments.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

TABLE 4–2 Studies of Biological Agents on Commercial Aircrafta

Reference

Flights, Aircraft

Biological Agents

Sampler, Sampling Location, Flight Segment

Findings

Authors’ Conclusions

Nagda et al. (1989, 1992)

92 flights (23 smoking, 8 international)

12 airlines

Airbus; B727, B737, B747, B757, B767; DC8, DC9, DC10; L1011

(Study conducted in 1989)

Culturable airborne bacteria, fungi

Rank-order comparisons

Multiple-hole impactor (SAS Compact) (90 L/min for 0.67, 1.0, 1.3, 2.0, 3.0 min)

Smoking flights: middle of nonsmoking section, rear of aircraft (smoking section)

Nonsmoking flights: middle of aircraft

Near end of flight, before descent

Concentrations of both agents generally were higher with higher passenger loads.

Concentrations of bacteria were higher than those of fungi and were somewhat higher in smoking sections, on wide-body aircraft, on aircraft with recirculation, and on flights with lower nominal air-change rates.

Bacteria and fungi typically encountered in indoor environments that are characterized as “normal” were also found in cabin air with similar prevalences and at similar concentrations.

Neither bacteria nor fungi were present at concentrations generally thought to pose a risk of illness.

No actions need be taken to reduce prevailing concentrations of bioaerosols.

ATA (1994)

35 domestic flights

8 airlines

No recirculation, B727, DC9

Culturable airborne bacteria, fungi

Multiple-hole impactor (SAS Compact) (90 L/min for 1.3 min)

2 locations in first class; 2 locations in front, center, and rear of coach class

All concentrations were below 1000 CFU/m3 and were proportional to number of cabin occupants.

Concentrations of both agents were somewhat higher earlier in flights and in coach.

People and their activities were source of most contaminants.

Concentrations of contaminants in aircraft cabins are not likely to cause adverse health effects.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Reference

Flights, Aircraft

Biological Agents

Sampler, Sampling Location, Flight Segment

Findings

Authors’ Conclusions

ATA (1994)

Recirculated air, B757, MD80

(Year not specified)

Purported NIOSH recommended exposure limit of 1,000 CFU/m3

Early and late phases of flight segments

Concentrations were relatively low for all aircraft types, seating configurations, flight durations, and airlines.

No agents of respiratory infections were isolated.

Removal of contaminants appears to be sufficient for both ventilation designs because contaminant concentrations were below those common in other indoor spaces.

Spengler et al. (1994, 1997)

22 domestic flights

8 airlines

A300, A320; B727, B737, B747, B757, B767; DC9, DC10; MD80

(Study conducted in 1994)

Culturable airborne bacteria; culturable fungi in dust; cat and mite allergens in dust; endotoxin in dust

Concentrations in other public transportation-vehicles

Multiple-hole impactor (Burkard) (44–52 L/min for 2 min)

Coach section, front and rear

Terminal before boarding, onboard before takeoff, during cruise, during taxiing to gate; occasionally during deboarding (ground)

Dust samples (12 flights): 4–5 min samples from carpet and seat

(Findings applicable to both Spengler et al. 1994, 1997 and Dumyahn et al. 2000)

Concentrations of bacteria and fungi in air and fungi in dust were not significantly different across vehicle type with exception of bacteria during aircraft deboarding.

Concentrations of bacteria tended to be higher on planes with air recirculation.

For ground-transportation vehicles, highest concentration of bacteria was observed in subways, but airborne fungi were found most often in trains.

(Authors’ conclusions applicable to both Spengler et al. 1994, 1997 and Dumyahn et al. 2000)

Concentrations of biological agents in vehicles were generally lower than those common in homes and outdoor air, and none was present at concentrations that can be considered to present an unusual exposure risk. Bacterial and viral respiratory agents were not measured.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Dumyahn et al. (2000)

27 segments: 6 domestic flights, 6 interstate train trips, 7 interstate bus trips, 2 commuter train trips, 6 subway trips

B777

(Study conducted in 1996)

Culturable airborne bacteria; culturable fungi in air and dust

Concentrations in other public-transportation vehicles

Multiple-hole impactor (44 L/min for 1 min)

Rear of aircraft; center of buses, subway, train cars

Immediately after departure (ground), mid-trip (about 60 min prior to landing), immediately on touchdown

Dust samples: 1–3 m2; 4– 6 seats per travel segment per vehicle

Bacteria were typical of human sources.

Similar species of fungi were isolated on all vehicle types.

Cat allergen was detected in most samples and exceeded concentration considered high in two subway samples and one train sample.

Identifying effects of relative humidity, temperature, air movement patterns, and occupancy rates could be critical to understanding potential spread of infectious agents.

Wick and Irvine (1995)

44 flights (38 domestic, 4 intercontinental, 2 international)

1 airline

B727, B737, B767; BAe 146; DC10; MD80; SWM

Culturable airborne bacteria, fungi

Concentrations in common urban locations

Centrifugal impactor (RCS) (40 L/min for 4 min)

9 domestic, 2 international flights: first class, coach, galleys

4 intercontinental flights: multiple time intervals in flight

Higher bacterial and fungal concentrations were observed during periods of higher passenger activity.

Little difference was seen in concentrations of airborne bacteria or fungi between locations.

Concentrations on aircraft were highest 30 cm above floor near exhaust vents.

Concentration of microorganisms in U.S. aircraft cabin air is much lower than in ordinary city locations and does not contribute to risk of disease transmission among passengers.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Reference

Flights, Aircraft

Biological Agents

Sampler, Sampling Location, Flight Segment

Findings

Authors’ Conclusions

Wick and Irvine (1995)

(Study begun in 1987)

 

Various times: municipal buses, shopping mall, downtown sidewalk, airport departure lounge

 

 

Dechow (1996), Dechow et al. (1997)

14 scheduled intercontinental flights

2 airlines

A310 (trans-Mediterranean), A340 (trans-Atlantic)

(Study conducted in 1995)

Culturable airborne bacteria, fungi

German guidelines for hospital operating rooms (<50 CFU/m3), dispensaries, nurseries, and intensive care units (<150 CFU/m3)

Slit impactor FH2 (50 L/min for 2 min)

Cockpits, galleys, toilets, all classes of passenger cabins, supply air

Various times on ground and during flight

Fungal concentrations were extremely low, but bacterial concentrations frequently exceeded the limits for hospital air.

Highest bacterial concentrations were observed early in flight and during deboarding.

Bacterial concentrations were lowest in cockpits; concentrations in economy class and galleys were higher than in business or first class.

Bacteria were mainly nonpathogenic types.

Occupants are main source of airborne culturable bacteria.

Exposures to fungi on aircraft have no health significance.

Only health risk posed by biological agents on aircraft is person-to-person contact as in sneezing or coughing, with transmission over short distances.

Apprehension about increased infection risk compared with other crowded spaces is not reasonable.

Lee et al. (1999, 2000)

3 flights

1 airline

Culturable airborne bacteria, fungi

Multiple-hole impactor (Burkard) (10 L/min; sampling time not reported)

All concentrations of bacteria and fungi were below 1000 CFU/m3.

In general, aircraft air quality was satisfactory.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

 

B747

(Study conducted 1996–1997)

Hong Kong IAQ guideline (1000 CFU/m3)

One sampling location each flight (usually business class, otherwise center of economy class)

Immediately after takeoff, middistance, before landing

Highest concentrations were measured at beginning and end of flights (i.e., during boarding and deplaning).

Biological concentrations were generally low, and highest ones were associated with passenger activity.

ASHRAE/ CSS (1999), Pierce et al. (1999), Janczewski (2001)

8 flights (4 domestic, 4 international)

B777

(Study conducted in 1998)

Culturable airborne bacteria, fungi

Concentrations in buildings

Multiple-hole impactor (SAS Compact) (90 L/min; total air volume, 123 L)

One coach location each flight (5 forward, 3 rear)

During boarding, in flight, during deplaning

Concentrations of bacteria and fungi were relatively low compared with typical indoor concentrations.

Concentrations were highest during boarding and deplaning.

No infectious bacterial agents were isolated; two potentially infectious fungal agents (Aspergillus niger, Paecilomyces variotti) were isolated.

Data were not sufficient to draw definitive conclusions about air quality on commercial aircraft; however, available information indicated that no significant air quality health hazards were present for either passengers or crew.

Risk of disease transmission via aircraft ventilation system is low, but there is potential for disease transmission because of proximity of passengers; increasing amount of outside air will not minimize this type of disease transmission.

aCulturable bacteria and fungi from air samples reported as colony-forming units per unit volume of air (CFU/m3).

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×
  • None of the bacteria and few of the fungi were considered potential infectious agents.

  • Higher concentrations of culturable bacteria and fungi on aircraft were observed:

    • During periods of passenger activity (e.g., boarding and deplaning).

    • With higher passenger loads and in coach or economy class or the rear of aircraft, compared with first or business class.

    • When cabin air was recirculated or air change rates were lower.

    • Near the cabin floor (in the exhaust air stream).

  • No statistically significant differences in concentrations of culturable bacteria and fungi were observed:

    • Among different aircraft, airlines, or flight durations.

    • Between aircraft cabins and other types of public-transportation vehicles.1

    • Between aircraft cabins and typical indoor and outdoor urban environments.1

Sampling for Allergens

Few studies have measured the concentrations of allergens in aircraft cabins. (The allergen content of settled dust is reported as the amount of an agent per unit amount of settled dust—typically micrograms per gram (μg/g)). Wickens et al. (1997) found that the concentration of dust mite allergens was much lower in public places (including aircraft) than in homes. Dumyahn et al. (2000) found similar concentrations of dust mite allergens in samples from aircraft and other transportation vehicles; the concentration of cockroach allergens on the four flight segments that were tested was close to the detection limit of the assay method—essentially nonquantifiable.

Cat allergen was found in low to moderate concentrations in all of the vehicles that Dumyahn et al. (2000) tested. The concentrations on trains and subways and in living rooms occasionally exceeded 8 μg/g, the concentration of cat allergen associated with sensitization (Chapman 1995; Gelber et al. 1993). In the four aircraft that Dumyahn et al. (2000) sampled, the average concentration of cat allergen in cabin air was higher than the average for 24

1  

Concentrations on aircraft often were lower than those in other locations.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

homes even though no cats were on any of the flights. If a cat had been present, the concentration of cat allergen can be expected to be even higher (Chew et al. 1998) and conceivably could put sensitive individuals at risk of responding.

Evaluation of Available Information on Bioaerosols

Data on some biological agents in commercial aircraft cabins now are available as a result of the studies (see Tables 1–2 and 4–2) that were conducted after the publication of the previous NRC report (NRC 1986). Findings are consistent with patterns that have been observed in other occupied indoor environments. The bioaerosol data that have been collected on aircraft, however, are of little value for the estimation of acute hypersensitivity disease and respiratory infections, which might be the most important health risks associated with bioaerosol exposures in this environment. A discussion of acute hypersensitivity disease and respiratory infections related to bioaerosol exposures in commercial aircraft is presented later in this chapter.

Microorganisms Sampled in Cabin Air

All the bioaerosol samples described in Table 4–2 were grab samples (discrete, short-term samples of relatively small volume). The brief sampling times (up to 3 min) allow identification of rapid changes in bioaerosol concentrations but do not provide information on exposures throughout a flight unless sequential samples are collected. The number of samples collected per flight generally has been small, few replicates have been collected, and estimates of the variability within and between aircraft are poor.

As can be seen in Table 4–2, bioaerosols have only been measured with instruments that impact airborne particles directly onto agar and using culture media and incubation conditions that support the growth of broad groups of bacteria and fungi. Viruses have not been sampled because of practical difficulties.

Culture-based analysis was used in all studies of cabin air as an indication of exposure to microbial aeroallergens (especially fungal allergens). The viability of airborne bacteria and fungi was used as a surrogate measure of their infective potential, even though culture sampling is not a good method of measuring airborne exposure to microbial allergens or infectious agents. It seri

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

ously underestimates the concentrations of microorganisms in environmental samples because many microorganisms grow poorly under laboratory conditions and some important infectious agents require special growth media or incubation conditions. Most bacteria that have been isolated in aircraft cabins represent normal human flora, reflecting human occupancy and activity, but they do not necessarily predict the presence of infectious agents that people release. Furthermore, the allergenic, inflammatory, toxic, or irritant properties of environmental microorganisms are not related to cell viability. Therefore, bacteria or fungi that may have been present in cabin air and could have had serious health effects in earlier studies would have been missed because of the inappropriate detection methods that were used.

Other Biological Agents

Studies of bioaerosols on aircraft have been interpreted in terms of potential infection but have not considered the risks of inflammation, irritation, or toxicity. All but one of the studies in Table 4–2 also ignored the potential role of biological agents other than microbial agents, such as bacterial endotoxin, fungal toxins, and microbial volatile organic compounds.

Bacterial Endotoxin

Inhalation of endotoxin has been linked causally with acute airflow obstruction and airway inflammation (Rylander 1994; Milton 1996). Although dust samples have been collected for comparison of endotoxin content in aircraft and other vehicles (Spengler et al. 1997; Dumyahn et al. 2000), no information has been published on the endotoxin content of those samples. Because of a lack of data, it is not yet possible to determine whether endotoxin concentrations in aircraft cabins are high enough to be associated with adverse health effects. An ongoing NIOSH study is expected to provide relevant data on endotoxin concentrations in aircraft cabins (Waters et al. 2001).

Fungal Toxins

Low-molecular-weight fungal products that have toxic effects are called mycotoxins. There are no aircraft cabin air-quality studies in which airborne or dust-associated fungal toxins were measured, although some fungal species

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

that are known to produce toxins (e.g., species of Aspergillus and Penicillium) have been isolated from this environment. Extensive fungal growth would be necessary for cabin occupants to be exposed to high concentrations of fungal toxins, and it is not known whether inhalation exposures to mycotoxins on aircraft ever reach the levels that have been associated with adverse health effects.

Microbial Volatile Organic Compounds (MVOCs)

MVOCs, which often have distinctive odors, are under study as possible markers of microbial growth (Batterman 1995; Ammann 1999; Fischer et al. 1999). When more is known about the production of these compounds and their health effects, measurement of them might allow identification of aircraft in which there are substantial reservoirs of microbial growth.

Recommended Sampling for Biological Agents

Bioaerosol sampling on commercial aircraft has been broadly based. If the prevalence of biological agents in the cabins of commercial aircraft is to be understood, rigorous studies focused on specific biological agents are needed. In this section, the committee offers suggestions for the types of studies that should be conducted.

NIOSH-Sponsored Review

NIOSH contracted with researchers from the University of Colorado to review the available studies on bioaerosol exposures in aircraft and to provide recommendations on the need for and design of studies (Hernandez and Swartz 2000). These recommendations covered what microorganisms should be sampled, and why? When, where, and how in an aircraft should the sampling be conducted? How many samples should be taken? What types of aircraft and duration of flights should be sampled.

Hernandez and Swartz (2000) recommended that microorganisms be collected in ways that allow analysis with a variety of methods (e.g., culture, staining and direct microscopic examination, immunoassay, chemical assay, nucleic acid amplification, and other molecular detection methods). High-

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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volume air sampling (≥100 L/min) may be needed in aircraft cabins for detection limits to be low enough to yield useful exposure information. It was also recommended that studies of aircraft air quality not include endotoxin, fungal toxins, or other microbiological agents (e.g., fungal glucans) until assays for these materials are better developed and more evidence is available to suggest that these compounds are present in aircraft cabins at concentrations sufficient to cause adverse health effects.

Hernandez and Swartz (2000) further recommended that future bioaerosol monitoring focus on some of the newest and oldest aircraft in service (the Boeing 747–400 and 727 series aircraft, respectively) and account for the following factors: extremes in air recirculation rates and replenishment of fresh air, operation of air filtration systems, medium and long flight duration (1– 4 h and over 5 h of stable cruise time, respectively), and passenger load. They suggested that monitoring be conducted in the coach cabin with composite samples collected throughout a flight.

Allergens

Studies of common allergens in aircraft cabins are insufficient to assess the risk posed by allergen exposures on aircraft. Allergens usually are measured through analysis of dust rather than air samples because few of the particles carrying allergens are fine enough to remain airborne for more than a few min. Dust samples, however, can be used only to estimate the potential for allergen exposure rather than actual exposure, because the concentration of an allergen in dust does not take into account other factors that may influence exposure, such as the total density of dust on surfaces or its resuspension rate. More-sensitive analytical methods soon may make air sampling feasible, yielding better measurements of airborne allergens.

Infectious Agents

More information is needed on the frequency with which people are exposed to human infectious agents during air travel. Environmental sampling for infectious agents is problematic, however, because of the unpredictable presence of infectious persons, the many agents that travelers may carry, the different volumes of air that would need to be collected to detect different microorganisms given their wide range of release rates and infectious doses

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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(the number of cells required to cause infection), and difficulties related to capturing airborne bacteria and viruses and preserving their biological activity for accurate identification and enumeration. Nevertheless, it may be possible to assay concentrated, large-volume air samples with methods that do not rely on culture, such as nucleic acid amplification assays, which are available for many of the infectious agents to which people may be exposed on aircraft (Mastorides et al. 1999; Schafer et al. 1998; Aintablian et al. 1998; Echavarria et al. 2000). MacNeil et al. (1995) have reviewed these methods and their application to the evaluation of indoor air quality.

The presence of infectious agents in cabin air also can be recognized by indirect methods, such as surveillance for disease transmission or isolation of microorganisms from passengers and crew members. Clinical specimens (e.g., throat cultures or sputum samples) have been collected from recent air travelers to isolate specific infectious agents (Clayton et al. 1976; Moser et al. 1979; Brook, 1985; Klontz et al. 1989; Brook and Jackson 1992; Sato et al. 2000; CDC, 2001 a). Immunological tests on blood samples can also be used to identify infection, and tuberculin skin testing is a valuable tool to identify recent infection in studies of possible tuberculosis transmission.

Release of tracer particles and modeling of particle dispersion in aircraft cabins also may play a role in the assessment of the spread of infectious agents and other biological materials generated by cabin occupants and their activities. NIOSH is modeling airflow and migration of airborne biological agents throughout typical aircraft cabins. With this model, exposures for crew members and passengers could be estimated and measures to minimize such exposures could be evaluated. Similarly, the effect of passenger-controlled air supply (gaspers) on the distribution of aeroallergens and infectious agents could be assessed (BRE 2001).

HEALTH EFFECTS OF EXPOSURE TO BIOAEROSOLS

The principal biological contaminants of potential concern in cabin air are allergens and infectious agents. Substantial numbers of individuals are sensitive to one or more airborne allergens. Several common allergens have been detected in aircraft cabins (e.g., cat and dust mite allergens). Peanut-allergic passengers have raised concerns about potential contact, accidental ingestion, and inhalation exposure to allergens released from peanuts that are served on aircraft.

Respiratory infections are fairly common in humans. For example, adults

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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annually experience one to six colds and infants and children may have two to six episodes of acute, febrile, respiratory disease a year (Chin 2000). Persons with influenza, measles, tuberculosis, and meningococcal disease are known to have traveled on commercial aircraft while infectious and evidence of transmission of the causative agents during air travel is convincing for the first three diseases.

This section addresses the allergens of greatest potential concern in aircraft cabins, describes investigations that have been conducted of possible exposures to infectious agents on aircraft, and describes how exposures to biological agents in aircraft cabins can be controlled.

Hypersensitivity Disease

Immediate hypersensitivity involves stimulation of immunoglobulin E (IgE) antibodies. The condition occurs in persons who are genetically predisposed to mount an IgE response to specific allergens, have been exposed to a sensitizing dose of an allergen to which they are predisposed to respond, and are exposed appropriately to an allergen to which they previously were sensitized. An estimated 20% of Americans (over 50 million people) suffer from allergic rhinitis (hay fever) or other allergic diseases, and 8–17% of the population have asthma (IOM1993b; Montealegre and Bayona 1996; Bellanti and Wallerstedt 2000). Sensitivity to food allergens may induce asthma or anaphylactic reactions in some people, with the reaction triggered by ingestion or airborne exposure.

For passengers on aircrafts, the initial sensitizing steps in the development of immediate hypersensitivity are unlikely to occur during travel because passengers spend relatively little time in this environment. The situation could differ for a genetically susceptible crew member who had never previously encountered a common allergen but who was exposed repeatedly on aircraft. It is unlikely, however, that cabin personnel would have avoided exposure during childhood or early adult life to the allergens most likely to be present in aircraft.

The major allergens that appear to be involved in the development and exacerbation of asthma are those associated with dust mites and cockroaches, cats, dogs, other small animals, Alternaria species and other fungi, and pollen (IOM, 2000). Patterns of allergen sensitivity often change with age so that young children are more likely to become sensitized and to respond to either

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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dust mite, cockroach, or fungal allergens, whereas adults respond primarily to cat or pollen allergens (Silvestri et al. 1999; Dharmage et al. 2001).

A review of studies of health effects and pets concluded that cat and dog allergens are present everywhere as a result of people’s carrying allergen on their clothing and that all exposure to pets involves some risk of sensitization (Ahlbom et al. 1998). Cat allergens have been detected on people’s clothing (Tovey et al. 1995; D’Amato et al. 1997; DeLucca et al. 2000) and in places seldom visited by cats (e.g., office buildings, schools, new homes, allergists’ offices, hospitals, and shopping malls) (Lundblad 1991; Enberg et al. 1993; Hung et al. 1993; Janko et al. 1995). Hundreds of thousands of animals travel by air each year, but it is not known how often animals (particularly cats) travel in the cabins of commercial aircraft rather than the cargo bays. Thus, it is not surprising that cat and dust mite allergens have been detected in aircraft cabins (Wickens et al. 1997; Dumyahn et al. 2000). It also has not been determined if the presence of a cat measurably increases the concentration of cat allergen either in cabin air or settled dust. No conclusions can be reached regarding routine inhalation exposures to common animal, arthropod, or fungal allergens in aircraft because so few data are available (see the earlier section on sampling for allergens in aircraft cabins).

The few case reports that link hypersensitivity responses with allergen exposure on aircraft focus on peanut allergens. Hypersensitivity to peanuts is a foodborne allergy, and even minute ingested amounts can be extremely dangerous (Hourihane et al. 1997). An estimated 1% of Americans are hypersensitive to ground nut (peanut) or tree nut (e.g., walnut, almond, and cashew) allergens, so there is a sizeable health concern (Sicherer et al. 1999a). Aircraft passengers and crew members with life-threatening peanut allergies understandably are concerned about potential exposures on aircraft, where access to medical care is limited.

Sicherer et al. (1999b) published the first description of the clinical characteristics of allergic reactions to peanuts on commercial aircraft in subjects with peanut allergy. In a registry of 62 peanut- and tree-nut-sensitive people who had reported “airplane/airport” as a location where they had experienced allergic reactions, the authors reached 48. Reactions in 42 were thought to have begun on a plane including 34 reportedly allergic to peanuts. Among the 34, allergic responses were judged to have resulted from inhalation, ingestion, or skin contact in 14, 14, and 7 subjects, respectively.

A finding of the Sicherer et al. (1999b) investigation was that few affected passengers or their guardians had notified the flight crew or airline of their

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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suspected allergic reactions to peanuts (James 1999). Most of the reactions identified in the study were not life-threatening, but five of the subjects received epinephrine while in flight to manage severe allergic reactions. The authors concluded that exercising caution and having emergency medication available were important, considering the number of persons who may experience allergic reactions as a consequence of ingesting peanut or tree nuts or inhaling allergen on commercial aircraft. Emergency medical kits mandated for commercial aircraft in the United States include epinephrine to treat severe anaphylaxis (14 CFR121, Appendix A, First-Aid Kits and Emergency Medical Kits).

The Department of Transportation (DOT) proposed that airlines make “peanut-free zones” available on request from passengers with medically documented severe allergies to peanuts, as would be covered in the Air Carrier Access Act of 1986 (14 CFR 382, Nondiscrimination on the Basis of Disability in Air Travel). This proposal has not been implemented, although there is continued support for such a regulation and it could be reconsidered after submission to Congress of “a peer-reviewed scientific study that determines that there are severe reactions by passengers to peanuts as a result of contact with very small airborne peanut particles of the kind that passengers might encounter in an aircraft” (Resolution 117. Congressional Record, 105th Congress, 2nd Session, 1998). This committee was unable to locate such a study. The only studies that provide such evidence are the ones by Sicherer et al. (1999b) with self-reported symptom and exposure data, and a study in which peanut allergen was found on air filters from commercial aircraft (Jones et al. 1996), although this investigation was not published in a peer-reviewed journal. Overall, there is little evidence of responses in sensitized persons to airborne food allergens. Although rare, severe responses have been reported to cooking aerosols (e.g., from fish and hot dogs) (Crespo et al., 1995; Polasani et al., 1997), but not on aircraft. Major air carriers usually accommodate the requests of peanut-allergic travelers that peanuts not be served on a flight or in adjacent rows, and some airlines (e.g., United Air Lines, US Airways) have discontinued serving peanuts as snack foods.

Infectious Disease

The first NRC report on air quality in aircraft cabins included several recommendations for reducing the risk of transmission of infectious agents.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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The recommendations were based on incidents in which transmission was clear and on the environmental factors that had contributed to the spread of infectious agents during those events, such as insufficient outdoor air, lack of air treatment to remove infectious particles, and exposure to mosquitoes (NRC 1986). Since publication of the report, transmission of other infectious agents has been reported on aircraft, awareness of the importance of the subject for national and international public health has increased, and protocols for responding to the consequences of possible exposure to infectious agents on aircraft have been developed.

Large numbers of people use air travel for business, for tourism, and for other reasons (e.g., to immigrate or seek asylum) (WHO 1998a). An estimated 50 million North Americans will cross international borders in 2001; more than 10 million of them will travel to tropical destinations that pose a serious risk of infectious disease (Weiss 2001). On aircraft, people are confined in close quarters for long periods (see Chapter 1) and then disembark to many distant places (Wilson 1995). Thus, the risk of exposure to exotic infectious agents is higher for travelers than other persons, especially on international flights. Furthermore, the consequences of exposure to infectious agents may extend beyond the travelers to all others with whom they later have contact. Those factors give substantial public-health significance to the relationship between infectious diseases and air travel (Sato et al. 2000; BRE 2001; IEH 2001; Maloney and Cetron 2001).

Before air travel became the major medium of international travel, an infectious disease commonly had time to develop to its recognized clinical form before travelers reached their destinations (Grainger et al. 1995). But air travel is rapid, and people can complete a journey in the preclinical stage of an infectious disease (Clayton et al. 1976; Maloney and Cetron 2001). Furthermore, longer nonstop flights are becoming possible, and they increase the time that travelers spend together in an aircraft and the opportunities for exposure to infectious agents.

The reservoirs for infectious agents in cabin air are the people on board; the viruses, bacteria, and fungi they carry in and on their bodies; and vectors (such as arthropods) that may be found in aircraft. The infectious agents of concern in relation to cabin air are those transmitted by person-to-person droplet contact and airborne transmission of droplet nuclei. Droplet nuclei can remain suspended in cabin air and be distributed throughout an aircraft.

Studies of potential infectious disease transmission on aircraft are summarized in Table 4–3. Primary emphasis is on infectious agents that are known

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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TABLE 4–3 Investigations of Potential Infectious-Disease Transmission on Aircraft

Reference

Source cases

Travel history

Number

Outcome

Influenza

Moser et al. (1979)

21-y-old woman

Homer to Kodiak, Alaska (>3-h ground delay, cabin unventilated for 2 h), Boeing 737, 1977

49 passengers (1 not contacted) and 5 crew; 36 passengers and 2 crew members (72%) became ill; attack rate varied with time on grounded aircraft

Transmission likely to have occurred in closed, poorly ventilated, grounded aircraft and possibly in flight

Klontz et al. (1989)

11 persons actively coughing

Puerto Rico to Key West, Florida (2.5 h), DC-9, 1986

90 naval personnel; 23 (30%) of 77 susceptible persons became ill

Transmission likely to have occurred in flight; evidence of secondary transmission

Measles

Amler et al. (1982)

3 children, 1 with early symptoms

Venezuela to Miami, 1981

No information provided

Transmission suspected; evidence of secondary transmission

CDC (1983)

27-y-old man

San Diego to Seattle to San Diego, 1982

Infection in one passenger on return flight

Transmission may have occurred in flight or at airport; evidence of secondary transmission

Slater et al. (1995)

Not identified

New York to Tel Aviv (2-h ground delay, 10-h flight), Boeing 747, 1994

350 passengers; 8 cases identified

Transmission likely to have occurred in flight, but exposure in one of two airports also possible

Tuberculosis

Driver et al. (1994), CDC (1995)

Female flight attendant

39 international flights (U.S. to Europe or Mexico), 128 domestic flights; exposure duration of persons possibly infected, >1 h; median exposure duration of skin-tested passengers, 3.8 h; 1992

223 and 51 crew contacts; 212 exposed and 247 unexposed crew were skin-tested; 59 passengers were skin-tested

Infection of 2 crew members confirmed; evidence of transmission to passengers inconclusive

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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McFarland et al. (1993), CDC (1995)

Passenger, foreign-born

London to Minneapolis (9 h, seated in first class), 1992

325 passengers and 18 crew; 79 were skin-tested

No evidence of transmission

CDC (1995)

Passenger, foreign-born

Mexico to San Francisco (4.5 h) 1993

92 passengers; 22 were skin-tested

No evidence of transmission

CDC (1995), Miller et al. (1996)

Passenger, male Russian refugee

Frankfurt to New York (8.3 h), Boeing 767; New York to Cleveland (1.3 h), BAe 146; 1993

219 passengers and crew; 120 were skin-tested

Transmission to 2 persons could not be excluded, but likelihood was considered low

Moore et al. (1996)

Passenger, male

2 domestic flights (1.25 h each), Boeing 757, 1994

212 passengers and 15 crew; 100 were skin-tested

Transmission to 5 persons could not be excluded, but likelihood was considered low

CDC (1995)

Passenger, U.S. citizen, long-term resident in Asia

Taiwan to Tokyo (3 h), Tokyo to Seattle (9 h), Seattle to Minneapolis (3 h), Minneapolis to Wisconsin (0.5 h), 1994

661 passengers; 87 were skin-tested

Transmission could not be excluded, but likelihood was considered low

CDC (1995), Kenyon et al. (1996)

Passenger, 32-y-old Korean woman

Round trip: Honolulu to Chicago (8.4, and 8.75 h), Boeing 747–100, Chicago to Baltimore (1.75 and 2 h); Airbus 320–200, 1994

1,042 passengers and crew; 760 were skin-tested

Transmission to 5 passengers and 1 crew member could not be excluded

Wang (2000)

Passenger, 44-y-old Taiwanese woman

Los Angeles to Taipei (14 h) Boeing 747–400, 1997

308 passengers and crew; 225 were skin-tested

Transmission to 3 persons could not be excluded

Meningococcal Disease

CDC (2001c)

Passenger, 62-y-old man

Sydney, Australia to Los Angeles to New York, 2001

1 of 2 adjacent passengers was identified and remained asymptomatic

No evidence of transmission, but only adjacent passengers were followed

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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or suspected to have been transmitted in aircraft—influenza, measles, and tuberculosis—and those whose transmission is considered possible—meningococcal disease and acute respiratory infections. An infectious diseases was not considered if the disease is transmitted in a way unrelated to the cabin air or the ventilation system, release of an agent within an aircraft cabin results from an unprecedented event (e.g., an act of bioterrorism), or exposure during air travel is highly unlikely (e.g., viral hemorrhagic fevers or pneumonic plague) (Clayton et al. 1976; Fritz et al. 1996; Wenzel 1996; Withers and Christopher 2000; Maloney and Cetron 2001; Weiss 2001). Of the communicable diseases discussed in this report, tuberculosis, meningococcal meningitis, and plague are among the diseases for which there are special requirements related to travelers and the operation of conveyances (21 CFR 1240.50, 42 CFR 70.5, Certain Communicable Diseases; Special Requirements), and for which travelers can be detained to prevent the introduction, transmission, or spread of the disease in the United States (42 CFR 70.6, 21 CFR 1240.54, Apprehension and Detention of Persons with Special Diseases; 42 CFR 71.32, Persons, Carriers, and Things).

The risk of exposure to infectious persons is highest for the passengers seated closest to a source person and for the cabin crew who work in the same section (see the following section on cabin ventilation and exposure to bioaerosols). The risk of exposure to infectious agents may be higher for the cabin crew than for other passengers because the crew fly more often, and interact (if only briefly) with more persons on any given flight.

Influenza

Influenza is a highly contagious, viral respiratory illness. Influenza A and influenza B are the major types of influenza viruses that cause disease in persons of all ages (CDC 2001b,d). Influenza viruses are spread from person to person primarily via the airborne route after coughs and sneezes (Murphy and Webster 1996). The incubation period for influenza is 1–4 d (CDC 2001b,d) and the infectious period can start the day before symptoms begin until about 5 d after illness onset; children can be infectious for longer periods.

Influenza and Air Travel

Moser et al. (1979) reported on a 1977 outbreak of influenza among pas-

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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sengers and crew exposed to an acutely ill passenger aboard a 56-seat commercial jet that had a greater than 3-h ground delay before takeoff. The influenza attack rate among the passengers and crew was very high (38 of 53, 72%) and four persons required hospitalization. People who were on the disabled plane for more than 3 h had the highest attack rate (25 of 29, 86%). There was no significant association between illness and sex, smoking status, history of recent influenza vaccination, activity while waiting on the airplane, or later travel. The high attack rate was attributed to the ventilation system’s not operating during the ground delay and the doors’ being kept closed for about 2 h. The authors concluded that proper operation of the air circulation equipment and isolation of the ill passenger might have prevented this outbreak. The investigation led the first NRC committee to the conclusion: “Because a likelihood of occurrence of epidemic disease when forced-air ventilation is not available on the ground has been demonstrated, the Committee recommends…a regulation…that requires removal of passengers from an airplane within 30 min or less after a ventilation failure or shutdown on the ground and maintenance of full ventilation whenever onboard or ground air-conditioning is available” (NRC 1986). The 30-min limit was based on the time required to return a full load of passengers to a terminal. The FAA response to the recommendation was as follows: “Because the occurrence of complete ventilation cessation on passenger-laden airplanes is extremely rare and sometimes unavoidable, we do not believe that regulatory action is necessary. However, there may be value in bringing this concern to the attention of the air carriers. The FAA will advise air carriers of the need to deplane passengers, if possible, after 30 min without ventilation” (DOT 1987).

Suspected transmission of influenza associated with air travel also has been reported in association with an aircraft that had an operating ventilation system and no ground delay (Klontz et al. 1989). Ninety squadron members traveled on two DC-9 aircraft from Puerto Rico to a naval station in Key West, Florida. Twenty-three of 77 previously well persons on these 2.5-h flights developed severe influenza-like respiratory illness within 72 h of their return. Eleven of the case patients reported actively coughing during the return flight. A significant difference in risk of acquiring influenza was observed between the two aircraft—53% (18 ill of 34 susceptible persons) vs 12% (5 of 43)—and was related to the number of symptomatic persons on board—18% (8 of 44 passengers were ill during travel) vs 7% (3 of 46)—and occupant load factor—94% (44 passengers and 47 seats) vs 69% (46 of 67). The difference in attack rate remained greater in the first aircraft even if persons who had shared sleeping quarters with an ill person before air travel

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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were excluded—50% (10 of 20) vs 13% (4 of 30). Secondary transmission of influenza to family members and roommates was identified.

Public-Health Measures Related to Influenza and Travel

Immunization is the primary method used to prevent influenza infection and its complications (CDC 2001b,d) (see following section on control of exposure to biological agents). Annual influenza immunization has been recommended for tourism industry workers (Bodnar et al. 1999). Public-health authorities do not recommend general use of antiviral medications for all travelers to prevent influenza (in the event of immunization failure), because the drugs can have side effects and must be prescribed by a physician. However, antiviral medications might be appropriate during an influenza outbreak for unvaccinated travelers and persons who are at increased risk for influenza-related complications (CDC 2001d).

Measles

Measles is an acute, highly communicable viral disease with an average incubation period of 10–12 d (CDC 1998). It may be severe and frequently is complicated by middle ear infection or bronchopneumonia (CDC 2001b). Before widespread immunization, measles was common in childhood; 90% of people were infected by the age of 20. Since 1993, fewer than 1,000 measles cases have been reported each year (CDC 2001b), many of which are imported from outside the United States and occur among adults. Measles remains a common disease in many countries, including some developed countries in Europe and Asia, making exposure due to air travel a possibility.

Measles and Air Travel

Suspected transmission of measles at an airport and between passengers who shared a domestic flight has been reported (CDC 1983), and transmission also may have occurred in association with international air travel (Amler et al. 1982; Slater et al. 1995). Three children from Venezuela who entered the United States had measles later; one of them had early symptoms while on

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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board. The onset of rash in the other two cases was 12 d after the flight, and secondary transmission to other children was identified (Amler et al. 1982). Eight cases of measles were associated with a New York-Tel Aviv commercial flight, but no source case was identified (Slater et al. 1995). Transmission could have occurred during a 2-h ground delay (during which the aircraft’s air-conditioning system reportedly was not working) or during the 10-h flight.

Public-Health Measures Related to Measles and Travel

Immunization is the primary method used to prevent measles infection and its complications (Slater et al. 1995; CDC 1998, 1999, 2001b). Although vaccination against measles is not a requirement for entry into any country (including the United States), persons traveling abroad should ensure that they are immune. Most persons born before 1957 are likely to have had measles and generally are not considered susceptible. However, measles vaccine may be given to older persons if there is reason to believe that they may be susceptible and could be exposed during travel. Because the risk of contracting measles is greater in many countries than in the United States, infants and children should be vaccinated before leaving the United States, even if this involves vaccination at an earlier age than is recommended for infants and children remaining in the United States (CDC 2001b).

Tuberculosis

Tuberculosis (TB) is caused by Mycobacterium tuberculosis, a bacterium that can attack any part of the body but most frequently is associated with pulmonary infection. People typically become infected after spending a long time in a closed environment where the air is contaminated by a person with untreated tuberculosis who is coughing and has numerous organisms in secretions from the lungs (CDC 2001b). The time from exposure to detectable infection typically is 4–12 wk (Chin 2000). One-third of the world population of about 6 billion is estimated to be infected with M. tuberculosis (WHO 1998a), however, about 90% of otherwise healthy adults who acquire tuberculosis infection never develop active disease and therefore do not experience symptoms and are not infectious to others.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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Tuberculosis and Air Travel

The ease and availability of air travel, the large number of persons traveling yearly, the emergence of M. tuberculosis strains resistant to one or more of the primary drugs used for treatment, and the movement of immigrants and refugees increase the possibility for all persons to be exposed to someone with infectious tuberculosis (WHO 1998a). Tuberculosis is the most thoroughly studied communicable disease possibly associated with transmission during commercial air travel (Driver et al. 1994; CDC 1995; Kenyon et al. 1996; WHO 1998a) and the disease with the most-detailed formal guidelines for recognition and prevention (Withers and Christopher 2000; BRE 2001). No case of active tuberculosis has been identified as a result of exposure on a commercial aircraft, but the number of potentially exposed people who have been successfully screened in these investigations has been very small (see Table 4–3). One additional investigation showed no evidence of tuberculosis infection in 47 commercial airline pilots who flew DC-9-series aircraft (without air recirculation) in the company of a pilot with active tuberculosis (Parmet 1999).

In 1992–1995, CDC, in conjunction with state and local health departments, conducted seven investigations involving one flight attendant and six passengers with active tuberculosis (McFarland et al. 1993; Driver et al. 1994; CDC 1995; Kenyon et al. 1996; Miller et al. 1996; Moore et al. 1996). The number of potentially exposed passengers and crew was more than 2,600 on a total of 191 flights involving nine types of aircraft (WHO 1998a). In each investigation, the index case was considered to be highly infectious. Two of the passengers knew that they had active tuberculosis at the time of their flights to the United States. Diagnosis of the other five cases occurred after travel (CDC 1995). Only two of the seven investigations produced firm evidence to suggest transmission of M. tuberculosis infection: the first from a flight attendant to other crew members (Driver et al. 1994), the second from a passenger to other passengers (Kenyon et al. 1996). In the first report, evidence of transmission was limited to fellow crew members who were exposed to the infectious source for at least 12 h. In the second, transmission was demonstrated only to a few passengers seated close to the passenger with active tuberculosis (in adjacent rows in the same section) and on only one flight segment that lasted longer than 8 h.

Since 1995, one investigation has been conducted after identification of active tuberculosis in a passenger who traveled from Los Angeles to Taipei (Wang 2000). Skin-test conversion (a change in skin test status from negative

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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to positive) related to exposure during air travel could not be ruled out in three of 225 passengers. Although none of the three people was in same section of the aircraft as the index case, the author believed that exposure during the flight could not be excluded, because the cabins shared an air supply, the source person was highly infectious, and the flight was long. This investigation highlighted the value of two-step tuberculin skin testing used to differentiate between prior and recent infection. The 1-wk time interval between the first and second baseline skin tests in a two-step test is too short to identify recent infection but is sufficient to boost the weakened immune response of someone with prior infection. Eleven persons with negative initial skin tests showed positive reactions on their second baselines tests. These persons would have shown positive reactions on any later skin test (in an outbreak investigation, this typically would not be given until several months post exposure). Without the two-step baseline test, the apparent change in immune status of the 11 persons would have been mistakenly interpreted as possible travel-related infection, as happened in the investigation by Kenyon et al. (1996).

Public-Health Measures Related to Tuberculosis and Travel

A tuberculosis patient should not travel unless his or her physician judges it safe and should be instructed to cover coughs and sneezes with the hands or tissue paper at all times. Available data on the transmission of M. tuberculosis on aircraft indicate that the risk to passengers is no greater than is posed by other activities in which contact with potentially infectious individuals may occur (e.g., train travel, bus travel, and attending conferences) (Rogers 1962; Sacks et al. 1985; Lodi 1994; CDC 1995, 2001b; Moore et al. 1999; Witt 1999). There also is no evidence of increased risk to flight attendants, and routine and periodic tuberculin screening of flight crew is not justified or indicated for otherwise asymptomatic employees (Driver et al. 1994; WHO 1998a). However, air travelers who make frequent and regular stops in countries and areas with a high tuberculosis burden may be advised to have a baseline skin test to determine their infection status (CDC 2001b) and, if it is negative, to have periodic tests to identify subsequent exposure. The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) jointly developed guidelines for the prevention and control of tuberculosis during air travel and criteria for determining when followup of potential exposure is warranted (Table 4–4) (WHO 1998a).

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

TABLE 4–4 Criteria for Deciding to Inform Passengers and Crew Members of Possible Exposure to M. tuberculosis

Consideration

Criterion

Infectiousness of person identified as having had tuberculosis at time of air travel

Index case must be judged to have been capable of transmitting infection at time of travel on basis of clinical evidence and appropriate medical testing

Duration of exposure

At least 8 h

Interval between flight and notification of health authorities

No longer than 3 mo

Proximity of exposed persons to index case

Only passengers seated close to person with active tuberculosis and crew members working in same cabin need be informed initially

 

Source: Adapted from WHO (1998a).

Meningococcal Disease

Meningococcal disease is an acute bacterial infection characterized by sudden onset with fever, intense headache, nausea (often with vomiting), and stiff neck. The incubation period typically is 3 to 4 d but may range from 2 to 10 d (Chin 2000). Neisseria meningitidis is a leading cause of bacterial meningitis and sepsis in children and young adults in the United States and is spread through direct contact with respiratory secretions (CDC 2000). Case-fatality rates of meningococcal disease used to exceed 50%, but with early diagnosis, modern therapy, and supportive measures, they are now 5–15% (WHO 1998b; CDC 2001b). Up to 10% of populations in countries with endemic disease may be asymptomatic carriers of N. meningitidis.

Meningococcal Disease and Air Travel

Persons with meningococcal disease are known to have traveled on commercial aircraft (Duffy 1993; CDC 2001 c), and passengers next to an infected person on long flights may be at higher risk than other passengers for developing meningococcal disease (Maloney and Cetron 2001; CDC 2001c,e). However, no cases of transmission of N. meningitidis to fellow air travelers have been identified.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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Public-Health Measures Related to Meningococcal Disease and Air Travel

Prompt chemoprophylaxis of persons in close contact with an index-case patient is the primary means of preventing cases of meningococcal disease. CDC uses a passive-surveillance system by which local health departments report suspected cases of air-travel-associated meningococcal disease (CDC 2001c). CDC annually receives reports of about 12 cases of confirmed disease in which the index patient likely was contagious aboard an international conveyance (ship or aircraft) (CDC 2001c). In collaboration with the Council of State and Territorial Epidemiologists, CDC has developed procedures for the management of suspected exposure to N. meningitidis associated with air travel (CDC 2001e; CSTE 2001). In the absence of data on increased risk to other passengers, antimicrobial chemoprophylaxis is recommended only for passengers in seats next to an index case-patient (i.e., on either side of the potentially infectious person) (CDC 2001c).

CONTROL OF EXPOSURES TO BIOLOGICAL AGENTS

Hypersensitivity Diseases, Toxins, and Nuisance Agents

As discussed earlier, extensive microbiological growth in aircraft cabins appears to be unlikely. And there is no reason to think that the design, maintenance, or operation of the ventilation systems on commercial aircraft increase exposures to biological agents. Other than the identification of legionellae in cockpit humidifiers, bacterial or fungal growth in aircraft ventilation systems has not been reported.

Except for cat and peanut allergens, passengers appear to be the primary means of allergen entry into aircraft cabins. Therefore, exposure to allergens can be controlled only insofar as they are allowed to accumulate in dust that settles into upholstered furniture and onto carpeted floors and other surfaces and to the degree that allergenic particles are removed by filters in the return air system. High-efficiency filtration of cabin return air would remove essentially all potentially irritating, inflammatory, or toxic microorganisms and particles carrying allergens. Even lower-efficiency filters (e.g., 80–90% efficient) will remove most of the particles.

The presence of a cat in a cabin may be a more important source of cat allergen than what people carry into an aircraft. Persons who are hypersensi-

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

tive to cat allergen generally do not have cats in their homes, and those persons who are extremely sensitive restrict visits to places where they know that cats may be present. Therefore, limiting the number of cats or other pets that travel in aircraft cabins may reduce exposures that could have serious consequences.

Insufficient evidence is available to recommend eliminating peanut-containing food from being served to passengers on aircraft. But not serving peanuts to passengers adjacent to peanut-allergic travelers upon request would allay these person’s concerns and would reduce the chances for inhalation, contact, or accidental ingestion of peanut allergens that could result in severe adverse reactions.

Infectious Agents

Crew members and passengers on commercial aircraft can protect themselves and others from infectious diseases by adhering to current recommendations for immunization, practicing good personal hygiene, and not traveling when unwell (Slater et al. 1995; Rayman 1997; IEH 2001). Persons with communicable diseases that do not pose a direct threat to the health or safety of others cannot be denied access to air travel (14 CFR 382, Nondiscrimination on the Basis of Disability in Air Travel), although air carriers can impose restrictions (e.g., the wearing of a face mask) on persons with communicable diseases. Ill and well passengers have worn respiratory protection during air travel to avoid transmission of infectious agents, but the efficacy of this practice has not been demonstrated (Hendley 1987; Withers and Christopher 2000). Properly fitting respirators are likely to be uncomfortable, would stigmatize the wearer, and could impede communication; all these effects could reduce compliance.

Immunization against Infectious Diseases

The best means to protect travelers against vaccine-preventable diseases is immunization (Slater et al. 1995; Rayman 1997; Maloney and Cetron 2001). Table 4–5 lists the minimal, universally recommended immunizations for young children, adolescents, and adults. Influenza immunization also is recommended for persons younger than 65 who are at high risk of exposure and of exposing

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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TABLE 4–5 Universally Recommended Vaccinations for Children, Adolescents, and Adults

Population

Vaccination

All young children

Measles, mumps, and rubella

Diphtheria-tetanus toxoid and pertussis vaccine

Poliomyelitis

Haemophilus influenzae type B

Hepatitis B

Rotavirus

Varicella

Previously unvaccinated or partially vaccinated adolescents

Hepatitis B

Varicella (if no previous history of varicella)

Measles, mumps, and rubella

Tetanus-diphtheria toxoid (if not vaccinated during previous 5 years)

All adults

Tetanus-diphtheria toxoid

All adults aged 65 years and older

Influenza

Pneumococcal

 

Source: CDC (1999)

high-risk persons (CDC 2001d; Buxton et al. 2001). Selection of additional immunizations for travelers should be based on the requirements of the local health authorities at the travel destination and individual travelers’ risk of infection. Potential exposures to infectious agents during the time spent on an aircraft to reach a destination generally are not considered in these decisions, because the exposure time during flight relative to other travel-related exposures typically is brief.

Recognition of Potential Infection During or Shortly After Flight

Passengers and crew members occasionally become ill in flight. Persons with hypersensitivity diseases generally recognize the onset of allergic re-

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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sponses and asthma and carry appropriate medication to manage symptoms. Cabin crew usually can recognize passengers suffering from, for example, air sickness or excessive alcohol consumption. Persons suffering from diarrhea or vomiting and fever, with or without a skin rash, should be considered to be infectious (Grainger et al. 1995). Flight crew must notify the local health authority or quarantine officer at the airport where they are scheduled to land of arriving passengers who appear ill (e.g., with fever, rash, unusually flushed or pale complexion, jaundice, shivering, profuse sweating, diarrhea, or inability to walk without assistance) (Weiss 2001; 21 CFR1240.45 Report of Disease; 42CFR70 Interstate Quarantine; 42CFR71.21 (b) Foreign Quarantine). Recommendations have been formulated for responding to notification of the arrival of one or more ill travelers (Maloney and Cetron 2001; CDC 2001c,e). Those responses often can be initiated before an aircraft reaches an airport.

A WHO guideline (1998a) outlines basic actions that flight attendants should take when a person reports or is suspected of having tuberculosis during a flight. Many of the recommendations also would apply to other communicable diseases that are transmitted from person to person. For example, a symptomatic person should be isolated from other passengers, made comfortable, provided with tissues and waste containers, advised to move around the cabin as little as possible, and instructed to cover the nose and mouth when coughing.

State and local health departments and private physicians should ask all persons with infections that are transmitted by droplets and droplet nuclei about recent travel (WHO 1998a; CDC 2001 c). The case report forms that healthcare providers and laboratories are required to submit to local public health authorities for notifiable diseases should include information on recent travel.

In almost all of the investigations outlined in Table 4–3, the person’s infection was not detected until after the flight was completed and the passengers had dispersed. Notification of fellow travelers frequently has been hindered by difficulty in obtaining contact information for passengers. Airlines typically maintain passenger manifests and other records for 2–7 d, after which they are archived or destroyed. However, this period may be too short to allow follow up of infectious diseases with incubation periods longer than one wk (e.g., tuberculosis, measles, and possibly meningococcal disease). To facilitate timely identification and public health notification and management of at-risk passengers, airlines should ensure that electronic passenger manifests and contact information are preserved and readily available for a period of at least one month following disembarkation (CDC 2001c,e). WHO (1998a) recommends that airlines preserve for at least three years passenger records for flights involved in investigations of possible exposure to M. tuberculosis.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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Postexposure Prophylaxis (PEP)

Chemoprophylaxis may be recommended to prevent infection if exposure to some infectious agents (e.g., influenza viruses, N. meningitidis, and M. tuberculosis) is recognized during a flight or shortly thereafter. PEP is appropriate if exposure is judged to have been certain or highly likely, appropriate therapy is available and can be administered promptly, and the consequences of infection are sufficiently severe or the risk of complications from an infection is high.

Cabin Ventilation and Exposure to Bioaerosols
Ventilation Rate and Air Movement

Microorganisms can remain suspended in cabin air for long periods of time if there is little air movement or the exhaust rate is very low, as happened in an influenza outbreak on a grounded aircraft (Moser et al. 1979). Higher concentrations of airborne microorganisms have been measured on aircraft with higher passenger loads (Nagda et al. 1989, 1992) and in coach or economy class relative to business or first class (ATA 1994; Dechow et al. 1997; Dechow 1996; M.Dechow, Airbus, personal communication, January 3, 2001) (Table 4–2). Elevated concentrations of microorganisms also have been observed during periods of passenger activity, such as boarding and deplaning (Spengler et al. 1997; Wick and Irvine 1995; Dechow et al. 1997; ASHRAE/ CSS 1999; Pierce et al. 1999; Dumyahn et al. 2000; Dechow 1996, personal communication, January 3, 2001; Lee et al. 1999, 2000; Janczewski 2001). Nagda et al. (1989, 1992) observed higher concentrations of airborne bacteria, but lower concentrations of fungi, on flights with lower nominal air change rates. Wick and Irvine (1995) measured higher concentrations of bacteria near the floor vents than in the breathing zone of passengers. This observation, in conjunction with the available evidence that only persons seated near a source person are exposed to a sufficient number of bacteria or viruses to become infected, indicate that bioaerosols as small as droplet nuclei are readily entrained in moving air streams (see Figure 2–3). Therefore, the movement of bioaerosols along the length of aircraft cabins is likely restricted, and particles, including bioaerosols, are removed from the cabin with the exhaust or return air (see section on ventilation practices in aircraft cabins in Chapter 2).

On the issue of aircraft ventilation with regard to airborne infectious

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

agents, the 1986 NRC report recommended “that maximal airflow be used with full passenger complements to decrease the potential for microbial exposure and that recirculated air be filtered (to remove particles larger than 2–3 μm) to reduce microbial aerosol concentrations” (NRC 1986). The FAA does not require airlines to provide maximal air flow or filtration of recirculated air, but the latter has become common practice. Control of exposure to biological agents, except for bioeffluents as discussed in Chapter 2, is not a primary function of cabin ventilation. Nevertheless, increasing outside air ventilation or the amount of filtered recirculated air would decrease the mathematical probability of disease transmission in aircraft cabins by diluting airborne viruses or bacteria in a larger volume of microorganism-free air (see Equation 2–1). Although increasing cabin ventilation rates or changing the air mixing patterns are unlikely to prevent the transmission of infectious agents entirely, aircraft cabins should be provided with at least the minimal recommended supply of outside air whenever passengers are on board. If adequate ventilation cannot be provided, passengers should be deplaned and moved to a better-ventilated location, such as an airport terminal (NRC 1986; IEH 2001).

Recirculation of Cabin Air and Exposure to Infectious Agents

The practice of recirculating some cabin air has been questioned with regard to the transmission of infectious agents. Several studies measured higher concentrations of bacteria on aircraft that recirculated air (Nagda et al. 1989, 1992; Spengler et al. 1997), but no significant difference was observed in another study (ATA 1994). The higher bacterial concentrations could be due to a lower supply of outside air or low-efficiency or no filtration of return air on the aircraft that recirculated air. The seven investigations of possible transmission of M. tuberculosis on aircraft (Table 4–3) found no evidence that air recirculation facilitated transmission of the bacterium (CDC 1995; WHO 1998a). Similar rates of post-flight upper respiratory tract infections have been seen in travelers on flights with and without air recirculation, 18.5% (108 of 584 passengers) and 20.7% (106 of 516 passengers), respectively (J.Nutik Zitter, personal communication). Therefore, as has been seen in other public transportation vehicles, spread of airborne infectious agents in aircraft cabins appears to be limited to droplet and droplet nuclei transmission within close proximity (Rogers 1962; Sacks et al. 1985; Lodi 1994; Moore et al. 1999; Witt 1999).

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×
Treatment of Recirculated Air and Exposure to Infectious Agents

Some particles as small as single viruses pass through even HEPA filters because some viruses are near 0.3 μm in size, but the fraction of the total number of such particles that may penetrate a filter is negligible (see the discussion of recirculation in Chapter 2) (ASHRAE 2000). The use of ultraviolet germicidal irradiation (UVGI) for air disinfection has been suggested for aircraft cabins (Hendley 1987; Hall et al. 2000). Irradiation of return air to inactivate infectious agents in theory may be beneficial if an environmental control system (ECS) cannot accommodate a filter to treat recirculated air, but that method of air disinfection has not been demonstrated in aircraft (Slater et al. 1995). Use of UVGI in place of high-efficiency filtration is not recommended because irradiation would not remove the allergenic or toxic properties of biological particles. Although the potential benefit of the combined use of UVGI and HEPA filtration is not known (CDC 1994), any reduction in the concentration of viable airborne infectious agents beyond that provided by a HEPA filter would likely be insignificant and the survival time of microorganisms on filters is so short that killing them before or after collection on a filter is unnecessary. Use of germicidal lamps in the occupied space of an aircraft directly to irradiate cabin air, as is done in some high-risk health-care environments (CDC 1994), is not practical, because of the small volume of air that could be irradiated and necessary constraints on lamp placement to avoid direct human exposure to UVGI.

CONCLUSIONS

  • A person’s risk of acquiring an infection on an aircraft depends on several factors, such as the presence of an infectious person and release of infectious agents by that person, the ventilation rate and mixing of cabin air, the amount of air that is recirculated and how it is treated, proximity to the source person, duration of exposure, and susceptibility to the specific infectious agents. These factors could also increase inhalation exposure to allergens and other potentially hazardous biological materials generated by passengers and activities within aircraft cabins.

  • The proper design, operation, and maintenance of an aircraft ventilation system can limit but not eliminate the transmission of infectious agents and exposure to other biological agents on aircraft. Exposure to biological agents is increased when people are confined in an aircraft cabin without adequate ventilation.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Aeroallergens, Toxins, and Biological Irritants

  • Exposure of passengers to aeroallergens, toxins, and biological irritants from outdoor air on grounded aircraft likely would be similar to what they would encounter in an airport terminal or while traveling to and from an airport.

  • During flight, biological agents in aircraft cabins arise almost exclusively from inside sources rather than from outside air that is introduced through the ventilation system. People are a primary source of skin, scalp, nasal, and oral bacteria on aircraft, whereas most of the fungi and environmental bacteria in the cabin environment enter with outside air on the ground or are carried in by the occupants (e.g., on their shoes, clothing, or hand luggage).

  • Available bioaerosol data are of little value for the assessment of the quality of cabin air and the estimation of the magnitude of the health risks that may be associated with bioaerosol exposures (acute hypersensitivity and infectious disease). The need for measurements of inflammatory, irritant, or toxic biological agents (e.g., bacterial endotoxin or fungal toxins or glucans) can be determined better when the results of current studies become available.

  • Dust samples from commercial aircraft cabins have been analyzed for allergens and cat and dust mite allergens have been detected. There is limited evidence that individuals allergic to peanuts will respond to inhalation of, contact with, or accidental ingestion of airborne peanut allergens in the cabin environment.

Infectious Agents

  • Infectious agents can be transmitted from person to person aboard aircraft on the ground and during flight.

  • It is known that passengers and crew members with common respiratory infections occasionally travel while infectious. Passengers and cabin crew are exposed fairly often to the agents of common viral and bacterial infections and less often to the agents of more serious respiratory infections.

RECOMMENDATIONS

Aeroallergens, Toxins, and Biological Irritants

  • FAA and the airlines should work with the medical community to evaluate whether the presence of animals (other than service animals) in

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

passenger cabins on commercial aircraft can lead to allergic reactions in hypersensitive individuals.

  • FAA should conduct research to determine whether there is a potential for severe reactions by passengers with peanut allergies exposed to airborne peanut particles on aircraft. Until such research can be completed, airlines should consider complying with requests that peanuts not be served to passengers next to those passengers with peanut allergies.

  • Cabin crew should be trained to recognize and respond to the severe, potentially life-threatening responses (e.g., anaphylaxis or severe asthma attacks) that hypersensitive people may experience from exposures to airborne allergens.

Infectious Agents

  • Physicians treating persons with communicable diseases should discuss the advisability of air travel with them and should instruct their patients to take appropriate precautions that will protect other persons from infectious agents. In addition, physicians treating persons who are unusually susceptible to infectious disease should inform their patients of the potential risks associated with air travel and of the appropriate precautions that may protect susceptible persons from infection.

  • Health-care providers should obtain travel histories from persons with reportable infectious diseases and should notify public health authorities if a patient with a communicable disease recently has traveled. Public health authorities and air carriers should cooperate to notify air travelers as soon as possible if they may have been exposed to an infectious agent for which post-exposure prophylaxis may reduce the risk or the severity of an infection. Airlines should ensure that electronic passenger manifests and contact information is preserved and readily available for a period of at least one month following disembarkation to facilitate timely identification and notification of passengers who may have been exposed to an infectious agent during air travel.

  • Increased efforts should be made to provide cabin crew, passengers, and health professionals with information on health issues related to air travel. To that end, FAA and the airlines should work with federal and international agencies (such as the U.S. Public Health Service and WHO) and medical organizations (such as the American Medical Association, the Aerospace Medical Association, and the International Society of Travel Medicine) to

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

improve the awareness of health professionals of the need to advise patients of the risks posed by air travel.

REFERENCES

Ahlbom, A., A.Backman, J.Bakke, T.Foucard, S.Halken, I.M.Kjellman, L.Malm, S. Skerfving, J.Sundell, and O.Zetterström. 1998. “NORDPET” pets indoors—A risk factor for or protection against sensitisation/allergy. Indoor Air 8(4):219–235.

Aintablian, N., P.Walpita, and M.H.Sawyer. 1998. Detection of Bordetella pertussis and respiratory synctial virus in air samples from hospital rooms. Infect. Control Hospital Epidemiol. 19(12):918–923.

Amler, R.W., A.B.Bloch, W.A.Orenstein, K.J.Bart, P.M.Turner Jr, and A.R.Hinman. 1982. Imported measles in the United States. JAMA 248(17):2219–2133.

Ammann, H.M. 1999. Microbial volatile organic compounds. Pp. 26.1–26.17 in Bioaerosols: Assessment and Control, J.M.Macher, H.M.Ammann, H.A.Burge, D.K.Milton, and P.R.Morey, eds. Cincinnati, OH: American Conference of Government Industrial Hygienists.

Arlian, L.G. 1999. House dust mites. Pp. 22.1–22.9 in Bioaerosols: Assessment and Control, J.M.Macher, H.M.Ammann, H.A.Burge, D.K.Milton, and P.R.Morey, eds. Cincinnati, OH: American Conference of Government Industrial Hygienists.

ASHRAE(American Society of Heating, Refrigerating and Air-Conditioning Engineers). 2000. Air cleaners for particulate contaminants in 2000 ASHRAE Handbook: Heating, Ventilating, and Air-Conditioning Systems and Equipment. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

ASHRAE/CSS (American Society of Heating Refrigerating and Air-conditioning Engineers and/Consolidated Safety Services). 1999. Relate Air Quality and Other Factors to Symptoms Reported by Passengers and Crew on Commercial Transport Category Aircraft. Final Report. ASHRAE Research Project 957-RP. Results of Cooperative Research Between the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., and Consolidated Services, Inc. February 1999.

ATA (Air Transport Association of America). 1994. Airline Cabin Air Quality Study. Submitted to: Air Transport Association of America, Washington, DC. April 1994.


Batterman, S.A. 1995. Sampling and analysis of biological volatile organic compounds. Pp. 249–268 in Bioaerosols, H.A.Burge, ed. Boca Raton: Lewis.

Bellanti, J.A., and D.B.Wallerstedt. 2000. Allergic rhinitis update: epidemiology and natural history . Allergy Asthma Proc. 21(6):367–370.

Bodnar, U.R., K.L.Fielding, A.W.Navin, S.A.Maloney, M.S.Cetron, C.B.Bridges, K. Fukuda, and J.C.Butler. 1999. Preliminary Guidelines for the Prevention and Control of Influenza-Like Illness Among Passengers and Crew Members on Cruise

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Ships. Division of Quarantine, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA. August.

BRE (British Research Establishment, Environment Division). 2001. Study of Possible Effects on Health of Aircraft Cabin Environments- Stage 2. British Research Establishment, Environment Division, Garston, Watford, UK. [Online]. Available: http://www.aviation.dtlr.gov.uk/healthcab/aircab/index.htm [posted September 2001].

Brook, I. 1985. Bacterial flora of airline headset devices. Am. J. Otolaryngol. 6(2):111– 114.

Brook, I., and W.E.Jackson. 1992. Changes in the microbial flora of airline headset devices after their use. Laryngoscope. 102(1):88–89.

Burge, H.A., W.R.Solomon, and J.R.Boise. 1980. Microbial prevalence in domestic humidifiers. Appl. Environ. Microbiol. 39(4):840–844.

Burton, N.C., and R.E.McCleery. 2000. Exposure potentials during cleaning, overhauling and repairing of aircraft lavatory tanks and hardware. Appl. Occup. Environ. Hyg. 15(11):803–808.

Buxton, J.A., D.M.Skowronski, H. Ng, S.A.Marion, Y.Li, A.King, and J.Hockin. 2001. Influenza revaccination of elderly travelers: antibody response to single influenza vaccination and revaccination at 12 weeks. J. Infect. Dis. 184(2):188–191.

CDC (Centers for Disease Control and Prevention). 1983. Epidemiological notes and reports. Interstate importation of measles following transmission in an airport– California, Washington, 1982. MMWR 32(16):210, 215–216.

CDC (Centers for Disease Control and Prevention). 1994. Emerging infectious diseases. Detection of notifiable diseases through surveillance for imported plague-New York, September-October 1994. MMWR 43(44):805–807.

CDC (Centers for Disease Control and Prevention). 1995. Exposure of passengers and flight crew to Mycobacterium tuberculosis on commercial aircraft, 1992–1995. MMWR 44(08):137–140.

CDC (Centers for Disease Control and Prevention). 1998. Measles, mumps, and rubella—vaccine use and strategies for elimination of measles, rubella, and congenital rubella syndrome and control of mumps: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR. 47(RR-8):1–59.

CDC (Centers for Disease Control and Prevention). 1999. Vaccine-preventable diseases: improving vaccination coverage in children, adolescents, and adults. A report on recommendations of the Task Force on Community Preventive Services. MMWR 48(RR-8):1–15.

CDC (Centers for Disease Control and Prevention). 2000. Prevention and control of meningococcal disease: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR. 49(RR07):1–10.

CDC (Centers for Disease Control and Prevention). 2001a. Public health dispatch: Update: assessment of risk for meningococcal disease associated with the Hajj 2001. MMWR 50(12):221–222.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

CDC (Centers for Disease Control and Prevention). 2001b. Health Information for International Travel 2001–2002. Atlanta, GA: U.S. Dept. of Health and Human services, Public Health Services, Centers for Disease Control and Prevention, National Center for Infectious Disease, Division of Quarantine.

CDC (Centers for Disease Control and Prevention). 2001c. Exposure to patients with meningococcal disease on aircrafts—United States, 1999–2001. MMWR. 50:485– 488.

CDC (Centers for Disease Control and Prevention). 2001d. Prevention and control of influenza. MMWR 50(RR04):1–46.

CDC (Centers for Disease Control and Prevention). 2001 e. Guidelines for the Management of Airline Passengers Exposed to Meningococcal Disease. [Online]. Available: http://www.cdc.gov/travel/menin-guidelines.htm. [June 2001].

Cetron, M., J.Keystone, D.Shlim, and R.Steffen. 1998. Travelers’ health. Emerg. Infect. Dis. 4(3):405–407.

Chapman, M.D. 1995. Analytical methods: immunoassays. Pp. 235–248 in Bioaerosols, H.A.Burge, ed. Boca Raton: Lewis.

Chew, G.L., H.A.Burge, D.W.Dockery, M.L.Muilenberg, S.T.Weiss, and D.R.Gold. 1998. Limitations of a home characteristics questionnaire as a predictor of indoor allergen levels. Am. J. Respir. Crit. Care Med. 157(5 Ptl):1536–1541.

Chin, J. 2000. Control of Communicable Diseases Manual: An Official Report of the American Public Health Association, 17th Ed. Washington, DC: American Public Health Association.

Clayton, A.J., D.C.O’Connell, R.A.Gaunt, and R.E.Clarke. 1976. Study of the microbiological environment within long- and medium-range Canadian Forces aircraft. Aviat. Space Environ. Med. 47(5):471–482.

Cooper, R.C., and R.E.Danielson. 1992. The Occurrence of Legionellaceae in Aircraft Water Supply and Humidifiers. UCB/SEEHRL No. 92–1. Sanitary Engineering and Environmental Health Research Laboratory (SEEHRL), College of Engineering, School of Public Health, University of California, Berkeley.

Crespo, J.F., C.Pascual, C.Dominguez, I.Ojeda, F.M.Munoz, and M.M.Esteban. 1995. Allergic reactions associated with airborne fish particles in IgE-mediated fish hypersensitive patients. Allergy 50(3):257–261.

CSTE (Council of State and Territorial Epidemiologists). 2001. Guidelines for management of contacts of a patient with meningococcal disease who has recently traveled by airline. [Online]. Available: http://www.cste.org/ps/2000/2000-id-02.htm. [June 2001].

Custovic, A., H.Woodcock, M.Craven, R.Hassall, E.Hadley, A.Simpson, and A. Woodcock. 1999a. Dust mite allergens are carried on not only large particles. Pediatr. Allergy Immunol. 10(4):258–260.

Custovic, A., B.Simpson, A.Simpson, C.Hallam, M.Craven, and A.Woodcock. 1999b. Relationship between mite, cat, and dog allergens in reservoir dust and ambient air. Allergy 54(6):612–616.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

D’Amato, G., R.Liccardi, M.Russo, D.Barber, M.D’Amato, and J.Carreira. 1997. Clothing is a carrier of cat allergens. J. Allergy Clin. Immunol. 99(4):577–578.

Danielson, R.E., and R.C.Cooper. 1992. Distribution of Legionellaceae in Aircraft Water and Humidified Air. University of California, Environmental Engineering and Health Sciences Laboratory, College of Engineering and School of Public Health, Berkeley, CA.

Dechow, M. 1996. Airbus Cabin Air Quality—Only the Best! FAST Airbus Technical Digest, December 1996.

Dechow, M. 2001. Response from Airbus to NAS questions following 3 January 2001 public session in Washington, DC. [unpublished].

Dechow, M., H.Sohn, and J.Steinhaus. 1997. Concentrations of selected contaminants in cabin air of airbus aircraft. Chemosphere 35(1–2):21–31.

De Lucca, S.D., T.J.O’Meara, and E.R.Tovey. 2000. Exposure to mite and cat allergens on a range of clothing items at home and the transfer of cat allergen in the workplace. J. Allergy Clin. Immunol. 106(5):874–879.

Dharmage, S., M.Bailey, J.Raven, T.Mitakakis, A.Cheng, D.Guest, J.Rolland, A. Forbes, F.Thien, M.Abramson, and E.H.Walters. 2001. Current indoor allergen levels of fungi and cats, but not house dust mites, influence allergy and asthma in adults with high dust mite exposure. Am. J. Respir. Crit. Care Med. 164(1):65–71.

DOT (Department of Transportation). 1987. Airline Cabin Air Quality. Report to Congress. Washington, DC: Department of Transportation, Federal Aviation Administration. February.

Driver, C.R., S.E.Valway, W.M.Morgan, I.M.Onorato, and K.G.Castro. 1994. Transmission of Mycobacterium tuberculosis associated with air travel. JAMA. 272(13):1031–1035.

Duffy, T.P. 1993. Clinical problem-solving. The sooner the better. N. Eng. J. Med. 329(1):710–713.

Dumyahn, T.S., J.D.Spengler, H.A.Burge, and M.Muilenburg. 2000. Comparison of the environments of transportation vehicles: results of two surveys. Pp. 3–25 in Air Quality and Comfort in Airliner Cabins, N.Nagda, ed. West Conshohocken, PA: American Society for Testing and Materials.


Echavarria, M., S.A.Kolavic, S.Cersovsky, F.Mitchell, J.L.Sanchez, C.Polyak, B.L. Innis, and L.N.Binn. 2000. Detection of adenoviruses (AdV) in culture-negative environmental samples by PCR during an AdV-associated respiratory disease outbreak. J. Clin. Microbiol. 38(8):2982–2984.

Enberg, R.N., S.M.Shamie, J.McCullough, and D.R.Ownby. 1993. Ubiquitous presence of cat allergen in cat-free buildings: probable dispersal from human clothing. Ann. Allergy 70(6):471–474.


Fischer, G., T.Muller, M.Moller, R.Ostrowski, and W.Dott. 1999. MVOC of fungiuse as an indicator for exposure level, [in German]. Schriftenr. Ver. Wasser Boden Lufthyg. 104:183–192.

Fritz, C.L., D.T.Dennis, M.A.Tipple, G.L.Campbell, C.R.McCance, and D.J.Gubler. 1996. Surveillance for pneumonic plague in the United States during an intema-

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

tional emergency: a model for control of imported epidemic diseases. Emerg. Infect. Dis. 2(1):30–36.

Gelber, L.E., L.H.Seltzer, J.K.Bouzoukis, S.M.Pollart, M.D.Chapman, and T.A.PlattsMills. 1993. Sensitization and exposure to indoor allergens as risk factors for asthma among patients presenting to hospital. Am. Rev. Respir. Dis. 147(3):573– 578.

Glines,C.V. 1991. Should long-range aircraft be humidified? Air Line Pilot. 60(3):30–32, 50.

Grainger, C.R., M.J.Young, and H.H.John. 1995. A code of practice on dealing with infectious diseases on aircraft. J. R. Soc. Health 115(3):175–177.


Hall, R.J., J.J.Sangiovanni, H.H.Hollick, T.N.Obee, and S.O.Hay. 2000. Design of air purifiers for aircraft passenger cabins based on photocatalytic oxidation technology. Pp. 135–160 in Air Quality and Comfort in Airliner Cabins, N.L.Nagda, ed. West Conshohocken, PA: American Society for Testing and Materials.

Hendley, J.O. 1987. Risk of acquiring respiratory tract infection during air travel. JAMA. 258(19):2764.

Hernandez, M., and M.Swartz. 2000. A Review of Sampling and Analysis Methods for Assessing Airborne Microbiological Contamination on Commercial Aircraft. A Literature Survey and Review. Draft Report to NIOSH per Order #0009936697, Requisition 9938VQC.

Hourihane, J.O’B., S.A.Kilburn, J.A.Nordlee, S.L.Hefle, S.L.Taylor, and J.O.Warner. 1997. An evaluation of the sensitivity of subjects with peanut allergy to very low doses of peanut protein: a randomized, double-blind, placebo-controlled food challenge study. J. Allergy Clin. Immunol. 100(5):596–600.

Hung, L.L., C.S.Yang, F.J.Dougherty, F.A.Lewis, F.A.Zampiello, and L.Mangiaracina. 1993. Dust mite and cat dander allergens in office buildings in the mid-Atlantic region. Pp. 163–170 in Environments for People. Proceedings of IAQ92 Conference, San Francisco, California. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.


IEH (Institute for Environment and Health). 2001. Consultation on the Possible Effects on Health, Comfort and Safety on Aircraft Cabin Environments. IEH Web Report W5. Leicester, UK: Institute for Environment and Health. [Online]. Available: http://www.le.ac.uk/ieh/webpub.html [posted March 2001]

IOM (Institute of Medicine). 1993a. Assessing exposure and risk. Pp. 185–205 in Indoor Allergens: Assessing and Controlling Adverse Health Effects, A.M.Pope, R.Patterson, and H.Burge, eds. Washington, DC: National Academy Press.

IOM (Institute of Medicine). 1993b. Magnitude and dimensions of sensitization and disease caused by indoor allergens. Pp. 44–85 in Indoor Allergens: Assessing and Controlling Adverse Health Effects, A.M.Pope, R.Patterson, and H.Burge, eds. Washington, DC: National Academy Press.

IOM (Institute of Medicine). 2000. Executive summary. Pp. 1–18 in Clearing the Air: Asthma and Indoor Air Exposures. Washington, DC: National Academy Press.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

James, J.M. 1999. Airline snack foods: tension in the peanut gallery. J. Allergy Clin. Immunol. 104(1):25–27.

Janczewski, J. 2001. Airline Cabin Air Quality Study. Consolidated Safety Services, Inc. Presentation to the NRC Committee on Air Quality in Passenger Cabins on Commercial Aircraft, January 3–4, 2001, Washington, DC.

Janko, M, D.C.Gould, L.Vance, C.C.Stengel, and J.Flack. 1995. Dust mite allergens in the office environment. Am. Ind. Hyg. Assoc. J. 56(11):1133–1140.

Jones, R.T., D.B.Stark, G.L.Sussman, S.Waserman, and J.W.Yunginger. 1996. Recovery of peanut allergens from ventilation filters of commercial airliners. J. Allergy Clin. Immunol. 97(1 Part 3):423.


Kenyon, T.A., S.E.Valway, W.W.Ihle, I.M.Onorato, and K.G.Castro. 1996. Transmission of multidrug-resistant Mycobacterium tuberculosis during a long airplane flight. N. Engl. J. Med. 334(15):933–938.

Kim, J. 1994. Atmospheric environment of bioaerosols. Pp. 28–67 in Atmospheric Microbial Aerosols: Theory and Applications, B.Lighthart, and A.J.Mohr, eds. New York: Chapman & Hall.

Klontz, K.C., N.A.Hynes, R.A.Gunn, M.H.Wilder, M.W.Harmon, and A.P.Kendal. 1989. An outbreak of influenza A/Taiwan/1/86 (H1N1) infections at a naval base and association with airplane travel. Am. J. Epidemiol. 129(2):341–348.


Lacey, J., and J.Venette. 1995. Outdoor air sampling techniques. Pp. 407–471 in Bioaerosols Handbook, C.S.Cox, and C.M.Wathes, eds. Boca Raton, FA: Lewis.

Lee, S.C., C.S.Poon, X.D.Li, and F.Luk. 1999. Indoor air quality investigation on commercial aircraft. Indoor Air 9(3):180–187.

Lee, S.C., C.S.Poon, X.D.Li, F.Luk, M.Chang, and S.Lam. 2000. Air quality measurements on sixteen commercial aircraft. Pp. 45–58 in Air Quality and Comfort in Airliner Cabins, N.L.Nagda, ed. West Conshohocken, PA: American Society for Testing and Materials.

Lighthart, B., and L.D.Stetzenbach. 1994. Distribution of microbial bioaerosols. Pp. 68–98 in Atmospheric Microbial Aerosols: Theory and Applications, B.Lighthart, and A.J.Mohr, eds. New York: Chapman & Hall.

Lodi Tuberculosis Working Group. 1994. A school- and community-based outbreak of Mycobacterium tuberculosis in Northern Italy, 1992–3. Epidemiol. Infect. 113(1):83–93.

Logan, N.A., and C.B.Turnbull. 1999. Bacillus and recently derived genera. Pp. 357– 369 in Manual of Clinical Microbiology, 7th Ed., P.R.Murray, E.J.Baron, M.A. Pfaller, F.C.Tenover, and R.H.Yolken, eds. Washington, DC: ASM Press.

Lundblad, F.P. 1991. House dust mite allergy in an office building. Appl. Occup. Environ. Hyg. 6(2):94–96.


MacNeil, L., T.Kauri, and W.Robertson. 1995. Molecular techniques and their potential application in monitoring the microbiological quality of indoor air. Can. J. Microbiol. 41(8):657–665.

Maloney, S.A., and M.S.Cetron. 2001. Investigation and management of infectious

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

diseases on international conveyances (airplanes and cruise ships). Pp. 519–530 in Textbook of Travel Medicine and Health, 2nd Ed., H.L.DuPont, and R.Steffen, eds. Hamilton, Ontario: BC Decker.

Masterton, R.G., and A.D.Green. 1991. Dissemination of human pathogens by airline travel. Soc. Appl. Bacteriol. Symp Ser. 20:31S-38S.

Mastorides, S.M.R.L.Oehler, J.N.Greene, J.T.Sinnott 4th, M.Kranik, and R.L.Sandin. 1999. The detection of airborne Mycobacterium tuberculosis using micropore membrane air sampling and polymerase chain reaction. Chest 115(1):19–25. Comment in Chest 116(4):1143–1145.

McFarland, J.W., C.Hickman, M.Osterholm, and K.L.MacDonald. 1993. Exposure to Mycobacterium tuberculosis during air travel. Lancet 342(8863):112–113.

Menzies, R, R.Tamblyn, P.Comtois, C.Reed, J.Pasztor, Y. St. Germaine, and F.Nunes. 1993. Case-control study of microenvironmental exposures to aero-allergens as a cause of respiratory symptoms-Part of the sick building syndrome (SBS) symptom complex. Pp. 201–210 in Environments for People, Proceedings of IAQ92 Conference, San Francisco, California. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Miller, M.A., S.E.Valway, and I.M.Onorato. 1996. Tuberculosis risk after exposure on airplanes. Tuber. Lung Dis. 77(5):414–419.

Milton, D.K. 1996. Bacterial endotoxins: a review of health effects and potential impact in the indoor environment. Pp. 179–195 in Indoor Air and Human Health, 2nd Ed., R.B.Gammage, and B.A.Berven, eds. Boca Raton: CRC.

Mohr, A.J. 1997. Fate and transport of microorganisms in air. Pp. 641–650 in Manual of Environmental Microbiology, C.J.Hurst, G.R.Knudson, M.J.McInerney, L.D. Stetzenbach, M.V.Walter, eds Washington, DC: ASM Press.

Montealegre, F., and M.Bayona. 1996. An estimate of the prevalence, severity and seasonality of asthma in visitors to a Ponce shopping center. P.R.Health Sci. J.15(2):113–117.

Moore, M., K.S.Fleming, and L.Sands. 1996. A passenger with pulmonary/laryngeal tuberculosis: no evidence of transmission on two short flights. Aviat. Space Environ. Med. 67(11):1097–1100.

Moore, M., S.E.Valway, W.Ihle, and I.M.Onorato. 1999. A train passenger with pulmonary tuberculosis: evidence of limited transmission during travel. Clin. Infect. Dis. 28(1):52–56.

Moritz, M., H.Schleibinger, and H.Ruden. 1998. Investigations on the survival time of outdoor microorganisms on air filters. Zentralbl. Hyg. Umweltmed. 201(2):125– 133.

Moser, R.M., T.R.Bender, H.S.Margolis, G.R.Noble, A.P.Kendal, and D.G.Ritter. 1979. An outbreak of influenza aboard a commercial airliner. Am. J. Epidemiol. 110(1):1–6.

Muilenberg, M.L. 1995. The outdoor aerosol. Pp. 163–204 in Bioaerosols, H.A.Burge, ed. Boca Raton: Lewis.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Murphy, B.R., and R.G.Webster. 1996. Orthomyxoviruses. Pp. 1397–1445 in Fields Virology, 3rd Ed., B.N.Fields, D.M.Knipe, P.M.Howley, R.M.Chanock, T.P. Monath, J.L.Melnick, B.Roizman, and S.E.Straus, eds. Philadelphia, PA: Lippincott-Raven.

Nagda, N.L., M.D.Fortmann, M.D.Koontz, S.R.Baker, and M.E.Ginevan. 1989. Airliner Cabin Environment: Contaminant Measurements, Health Risks, and Mitigation Options. DOT-P-15–89–5. NTIS/PB91–159384. Prepared by GEOMET Technologies, Germantown, MD, for the U.S. Department of Transportation, Washington DC.

Nagda, N.L., M.D.Koontz, A.R.Konheim, and S.K.Hammond. 1992. Measurement of cabin air quality aboard commercial airliners. Atmos. Environ. Part A Gen. Top.26(12):2203–2210.

NRC (National Research Council). 1986. Pp. 1–12,152–160 in The Airliner Cabin Environment: Air Quality and Safety. Washington, DC: National Academy Press.


Ormstad, H., E.Namork, P.I.Gaarder, and B.V.Johansen. 1995. Scanning electron microscopy of immunogold labeled cat allergens (Fel d 1) on the surface of airborne house dust particles . J. Immunol. Methods 187(2):245–251.


Parmet, A.J. 1999. Tuberculosis on the flight deck. Aviat. Space. Environ. Med. 70(8):817–818.

Pasanen, A.L., J.Keinanen, P.Kalliokoski, P.I.Martikainen, and J.Ruuskanen. 1993. Microbial growth on respirator filters from improper storage. Scand. J. Work Environ. Health 19(6):421–425.

Pierce, W., J.Janczewski, B.Roethlisberger, and M.Janczewski. 1999. Air quality on commercial aircraft. ASHRAE J. (Sept.):26–34.

Platts-Mills, T.A., and M.C.Carter. 1997. Asthma and indoor exposure to allergens. N. Engl. J. Med. 336(19):1382–1384.

Platts-Mills, T.A., W.R.Thomas, R.C.Aalberse, D.Vervloet, and M.D.Chapman. 1992. Dust mite allergens and asthma: report of a second international workshop. J. Allergy Clin. Immunol. 89(5):1046–1060.

Polasani, R., L.Melgar, R.E.Reisman, and M.Ballow. 1997. Hot dog vapor-induced status asthmaticus. Ann. Allergy Asthma Immunol.78(1):35–36.

Powell, G.S. 1994. Allergens. Pp. 458–475 in Physical and Biological Hazards of the Workplace, P.H.Wald, and G.M.Stave, eds. New York: Van Nostrand Reinhold.


Rayman, R.B. 1997. Passenger safety, health, and comfort: a review. Aviat. Space Environ. Med. 68(5):432–440.

Rogers, E.F.H. 1962. Epidemiology of an outbreak of tuberculosis among school children. Public Health Rep. 77(5):401–409.

Rylander, R. 1994. Endotoxins. Pp. 73–79 in Organic Dusts: Exposure, Effects, and Prevention, R.Rylander, and R.R.Jacobs, eds. Boca Raton: Lewis.


Sacks, J.J., E.R.Brenner, D.C.Breeden, H.M.Anders, and R.L.Parker. 1985. Epidemiology of a tuberculosis outbreak in a South Carolina junior high school. Am. J. Public Health. 75(4):361–365.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

Sato, K., T.Morishita, E.Nobusawa, Y.Suzuki, Y.Miyazaki, Y.Fukui, S.Suzuki, and K.Nakajima. 2000. Surveillance of influenza viruses isolated from travellers at Nagoya International Airport. Epidemiol Infect. 124(3):507–514.

Schafer, M.P., J.E.Fernback, and P.A.Jensen. 1998. Sampling and analytical method development for qualitative assessment of airborne mycobacterial species of the Mycobacterium tuberculosis complex. Am. Ind. Hyg. Assoc. J. 59(8):540–546.

Shieh, Y.S., R.S.Baric, and M.D.Sobsey. 1997. Detection of low levels of enteric viruses in metropolitan and airplane sewage. Appl. Environ. Microbiol. 63(11):4401–4407.

Sicherer, S.H., A.Muñoz-Furlong, A.W.Burks, and H.A.Sampson. 1999a. Prevalence of peanut and tree nut allergy in the US determined by a random digit dial telephone survey. J. Allergy Clin. Immunol. 103(4):559–562.

Sicherer, S.H., T.J.Furlong, J.DeSimone, and H.A.Sampson. 1999b. Self-reported allergic reactions to peanut on commercial airliners. J. Allergy Clin. Immunol. 104(1):186–189.

Silvestri, M., G.A.Rossi, S.Cozzani, G.Pulvirenti, and L.Fasce. 1999. Age-dependent tendency to become sensitized to other classes of aeroallergens in atopic asthmatic children. Ann. Allergy Asthma Immunol. 83(4):335–340.

Slater, P.E., E.Anis, and A.Bashary. 1995. An outbreak of measles associated with a New York/Tel Aviv flight. Travel Med. Int. 13(3):92–95.

Spengler, J, H.Burge, T.Dumyahn, C.Dalhstrom, M.Muilenberg, and D.Milton. 1994. Aircraft Cabin Environmental Survey—Executive Summary. Department of Environmental Health, Harvard University School of Public Health, Boston, MA. May 16, 1994.

Spengler, J., H.Burge, T.Dumyahn, M.Muilenberg, and D.Forester. 1997. Environmental Survey on Aircraft and Ground-Based Commercial Transportation Vehicles. Prepared for the Commercial Airplane Group, The Boeing Company, by Harvard School of Public Health, Harvard University, Cambridge, MA. May 31, 1997.

Squillace, S.P. 1995. Allergens of arthropods and birds. Pp. 133–148 in Bioaerosols, H.Burge, ed. Boca Raton, FL: Lewis.

Suda, T., A.Sato, M.Ida, H.Gemma, H.Hayakawa, and K.Chida. 1995. Hypersensitivity pneumonitis associated with home ultrasonic humidifiers. Chest 107(3):711– 717.

Tovey, E.R.A.Mahmic, and L.G.McDonald. 1995. Clothing-an important source of mite allergen exposure. J. Allergy Clin. Immunol. 96(6 Pt 1):999–1001.

Trudeau, W.L., and E.Fernández-Caldas. 1994. Identifying and measuring indoor biologic agents. J. Allergy Clin. Immunol. 94(2 Pt 2):393–400.


Wang, P.D. 2000. Two-step tuberculin testing of passengers and crew on a commercial airplane. Am. J. Infect. Control 28(3):233–238.

Waters, M., T.Bloom, and B.Grajewski. 2001. Cabin Air Quality Exposure Assessment. National Institute for Occupational Safety and Health, Cincinnati, OH., Federal Aviation Administration Civil Aeromedical Institute. Presented to the

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
×

NRC Committee on Air Quality in Passenger Cabins of Commercial Aircraft, January 3, 2001, Washington, DC.

Weiss, E.L. 2001. Epidemiologic alert at international airports. Pp. 530–533 in Textbook of Travel Medicine and Health, 2nd Ed., H.L.DuPont, and R.Steffen, eds. Hamilton, Ontario: BC Decker.

Wenzel, R.P. 1996. Airline travel and infection. N. Engl. J. Med. 334(15):981–982.

WHO (World Health Organization). 1998a. Tuberculosis and Air Travel: Guidelines for Prevention and Control. WHO/TB98.256. Geneva: World Health Organization.

WHO (World Health Organization). 1998b. Control of Epidemic Meningococcal Disease. WHO Practical Guidelines, 2nd Ed. WHO/EMC/BAC/98.3. Geneva: World Health Organization.

Wick, R.L., and L.A.Irvine. 1995. The microbiological composition of airliner cabin air. Aviat. Space Environ. Med. 66(3):220–224.

Wickens, K., I.Martin, N.Pearce, P.Fitzharris, R.Kent, N.Holbrook, R.Siebers, S. Smith, H.Trethowen, S.Lewis, I.Town, and J.Crane. 1997. House dust mite allergen levels in public places in New Zealand. J. Allergy Clin. Immunol. 99(5):587–593.

Wilson, M.E. 1995. Travel and the emergence of infectious diseases. Emerg. Infect. Dis. 1(2):39–46.

Withers, M.R., and G.W.Christopher. 2000. Aeromedical evacuation of biological warfare casualties: a treatise on infectious diseases on aircraft. Mil. Med. 165(11 Suppl):1–21.

Witt, M.D. 1999. Trains, travel, and the tubercle. Clin. Infect. Dis. 28(1):57–58.

Wood, R.A., A.N.Laheri, and P.A.Eggleston. 1993. The aerodynamic characteristics of cat allergen. Clin. Exp. Allergy. 23(9):733–739.

Suggested Citation:"4 Biological Agents." National Research Council. 2002. The Airliner Cabin Environment and the Health of Passengers and Crew. Washington, DC: The National Academies Press. doi: 10.17226/10238.
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Although poor air quality is probably not the hazard that is foremost in peoples’ minds as they board planes, it has been a concern for years. Passengers have complained about dry eyes, sore throat, dizziness, headaches, and other symptoms. Flight attendants have repeatedly raised questions about the safety of the air that they breathe.

The Airliner Cabin Environment and the Health of Passengers and Crew examines in detail the aircraft environmental control systems, the sources of chemical and biological contaminants in aircraft cabins, and the toxicity and health effects associated with these contaminants. The book provides some recommendations for potential approaches for improving cabin air quality and a surveillance and research program.

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