Review of the Department of Defense Enhanced Particulate Matter Surveillance Program Report (2010)

Epidemiologic studies have consistently found associations between short-term and long-term exposure to particulate matter (PM) and risks of morbidity and premature mortality (Dockery et al. 1993; Pope et al. 1995; Levy et al. 2000; Samet et al. 2000; Pope et al. 2002; Dominici et al. 2003; Katsouyanni et al. 2003; Pope and Dockery 2006). The range of adverse health effects associated with exposure to air pollution is broad, affecting the respiratory and cardiovascular systems (see Table 1-1 for an illustration of effects related to short-term and long-term exposure) (Alfaro-Moreno et al. 2007; Brook 2008; Craig et al. 2008).

Exposure to PM affects the health of children, the elderly, and those who have such conditions as cardiopulmonary disease. The risk of various adverse health outcomes increases with exposure concentration, and there is little evidence of a threshold below which no adverse health effects are expected (WHO 2005). Other variables that influence the nature and probability of health outcomes are the size fraction, the chemical composition, and the duration of exposure.

PM concentrations in epidemiologic studies are typically measured as PM₁₀ or PM _2.5, referring to particles that have an aerodynamic diameter of less than 10 μm or less than 2.5 μm. A metric less commonly used is total suspended particulates (TSP), a measure of all PM in the atmosphere that does not discriminate by size. PM₁₀ may deposit in the upper airways and lung, whereas fine particles (PM_2.5) can penetrate more deeply into the lung and may reach the alveolar region. In the atmosphere, fine particles remain suspended for days to weeks and can travel hundreds to thousands of kilometers, whereas coarse particles (2.5-10 μm in aerodynamic diameter) deposit rapidly on ground surfaces with lifetimes on the order of minutes to hours (Wilson and Spengler 1996).

PM originates from natural and human-made sources, and the composition and size of the particles depend on the source. Sources of coarse particles include resuspension of soil from roads and streets; disturbance of soil and dusts by agricultural, mining, and construction operations; and ocean spray (Wilson and Spengler 1996). Sources of fine particles include emissions from combustion of motor-vehicle fuel (EPA 2002, Pakbin et al. 2009, and Zhang et al. 2009); high-temperature operations such as smelters and steel mills; combustion of coal, oil, and wood; and atmospheric transformation products of nitrogen oxides, sulfur dioxide, and organics (Wilson and Spengler 1996).

There have been efforts to examine PM exposures in the Middle East, particularly with regard to how the composition and concentration of PM differ from those in the United States and other industrialized regions where fossil-fuel combustion and vehicle emissions are the primary sources of PM. In the Middle East, where climatic conditions may be more arid, PM sources may include dust storms, dust from motor-vehicle disturbance of the desert floor, agricultural activities, emissions from burn pits where trash is burned, lead-zinc smelters, battery-processing facilities, refineries, power stations, fertilizer plants, and emissions from vehicles that use leaded gasoline (UNEP 2007; Engelbrecht et al. 2009). Dust storms may carry pollutants great distances and in large amounts;

for example, it has been estimated that the average dust fallout along the coastal area of Kuwait may travel up to 1,000 tons/km² annually (UNEP 2002, 2007). Richards et al. (1993), who examined respiratory disease in military personnel in Saudi Arabia in the early 1990s, described the sandy conditions: “the sand in Saudi Arabia was a major problem for equipment maintenance personnel and a leading concern for the medical staff. The sand was often powdery in consistency, and entered, in varying degrees, all living and working areas” (p. 3).

A recent paper by Brown et al. (2008) characterized PM concentrations at three sites in Kuwait from 2004 to 2005 and found that the arithmetic mean PM₁₀ concentrations ranged from 66 to 93 μg/m³ and the annual average PM₁₀ concentrations at all three sites exceeded the World Health Organization air-quality guideline of 20 μg/m³. The arithmetic mean PM_2.5 concentration at the three sites ranged from 31 to 38 μg/m³, and all the sites had mean PM_2.5 concentrations more than double the annual U.S. National Ambient Air Quality Standard for PM_2.5 of 15 μg/m³. PM_2.5 made up 47% of PM₁₀ at two of the sites and 41% of PM₁₀ at the other site; in contrast, studies in the United States and Europe have shown fine particles to make up 60-75% of PM₁₀.

Brown et al. (2008) concluded that the overall higher concentrations of PM₁₀ and PM_2.5 compared with studies in the United States and Europe are partially explained by the resuspension of dust and soil from the desert crust. However, the high concentrations of such particulates as nitrate, sulfate, elemental carbon, organic carbon, and elements (for example, lead and sulfur) indicated substantial contributions from combustion sources, such as traffic and industry. The authors concluded that the PM concentrations are high enough to cause health effects on the Kuwaiti population. As illustrated by Brown et al. (2008), two significant sources of PM in the Middle East include combustion-related processes and dust storms. Because of the paucity of PM exposure assessment studies conducted in the Middle East, data collected in other regions (including the Middle East) are discussed below.

In studies conducted in the U.S. and in Cairo, Egypt, combustion-related sources of PM included emissions from vehicles, cooking, wood and natural-gas combustion, and open trash-burning (Gertler et al. 2000; EPA 2004; Abu-Allaban et al. 2007; Schauer et al. 2007; Zheng et al. 2007). Abu-Allaban et al. (2007) conducted a monitoring study in Cairo, Egypt, and used a chemical mass-balance model to estimate source contributions. Based on the model results, the authors found that PM_2.5 tended to be dominated by mobile-source emissions, open burning, and secondary species. In a review of 22 chemical-mass balance PM_2.5 and PM₁₀ source-apportionment studies in several countries (including the U.S., Canada, China, and South Africa), the largest contribution to fossil-fuel emissions in a majority of the studies was attributed to gasoline and diesel-vehicle exhaust rather than industrial sources with modernized controls for pol-

lution (Chow and Watson 2002). Lewtas (2007) observed that combustion emissions account for over half of ambient PM_2.5 and noted that the combustion of plastics, chemicals, and other wastes can lead to the formation of potentially hazardous pollutants. Studies conducted in U.S. cities have found similar results (Watson and Chow 2001; Maykut et al. 2003; de Kok et al. 2006; Schauer et al. 2007; Zheng et al. 2007). Many other pollutants in addition to PM are generated during combustion, including sulfur dioxide, nitrogen oxides, ozone, and volatile organic compounds.

A large body of research has shown a link between exposures to specific sources of air pollution and health effects. H. Chen et al. (2008) conducted a systematic review of the literature on associations between long-term exposure to air pollution and risks of nonaccidental mortality and the incidence and mortality from cancer and cardiovascular and respiratory disease. In addition to finding associations between exposure to PM_2.5 and increased risks from nonaccidental mortality and mortality from lung cancer and cardiovascular disease, the authors concluded that living close to busy traffic appeared to be associated with increased risks of the three outcomes. Short-term and long-term exposure to traffic-related pollution has been associated with increased morbidity and mortality (for example, Kunzli et al. 2000; Beelen et al. 2008a; Beelen et al. 2008b; Zhang et al. 2009). A health assessment by the U.S. Environmental Protection Agency (EPA 2002) suggested that acute exposure to diesel-engine exhaust causes transient irritation and inflammation, particularly in people who have allergies and asthma symptoms. That conclusion is supported by a recent study by Zhang et al. (2009) in London that showed significant decreases in forced expiratory volume in the first second (FEV₁) (3-4.1%) and forced vital capacity (FVC) (3.1-3.7%) and an increase in markers of airway inflammation in asthmatic people after short-term exposures to urban air pollution, including diesel exhaust on a busy urban street, compared to a control site without traffic.

Middleton et al. (2008) examined the effects of changes in daily concentrations of PM₁₀ and ozone on hospital admissions for respiratory and cardiovascular causes in Nicosia, Cyprus, from 1995 to 2004. They found that for every 10-μg/m³ increase in daily average PM₁₀ concentration, there was a 0.9% increase in all-cause admissions and a 1.2% increase in cardiovascular admissions. They also observed an increase in hospitalizations, particularly for cardiovascular causes, on dust-storm days. However, the authors cautioned that the possible health effects of dust storms have not been extensively studied.

Perez et al. (2008) found that during Saharan dust outbreaks, a daily increase of 10 μg/m³ in PM_10-2.5 increased daily mortality by 8.4% compared with 1.4% during non-Saharan dust outbreaks. In contrast, other studies have not found an association between high PM₁₀ concentrations and morbidity or mortality. A study in Spokane, Washington, found no association between days with

high PM₁₀ concentrations from windblown dust and mortality (Schwartz et al. 1999). In a study in the Greater Vancouver area, clouds of dust transported from the Gobi Desert to Canada showed no effect on hospital admission rates (Bennett et al. 2006); in the Coachella Valley of California, there was a slight reduction in the effect of PM on mortality on windy days (Ostro et al. 2000).

Several studies have investigated the health effects of Asian dust storms in Taipei, Taiwan. They examined the association between PM₁₀ and hospital admissions of residents of Taipei from 1996 to 2001, comparing hospital admissions during dust-storm episodes (index days) with admissions on days without dust storms (comparison days) (Chen and Yang 2005; Yang et al. 2005; Yang 2006; Cheng et al. 2008; Chiu et al. 2008; Yang et al. 2009). Average PM₁₀ concentrations on index days were 111.68 μg/m³, or 56.25 μg/m³ higher than on comparison days. Analyses indicated that Asian dust-storm events may result in an increase in daily hospital admissions for chronic obstructive pulmonary disease (Chiu et al. 2008), cardiovascular disease (Chen and Yang 2005), congestive heart failure (Yang et al. 2009), asthma (Yang et al. 2005), allergic rhinitis (Chang et al. 2006), conjunctivitis (Yang 2006), and pneumonia (Cheng et al. 2008), although none of the associations were statistically significant. The study authors noted that the lack of statistical significance may be the result of a lack of power due to an inadequate sample size for hospital admissions during dust-storm events.

Bell et al. (2008) conducted time-series analyses in Taipei, Taiwan, examining the association between various indicators of sandstorms and the pollutants nitrogen dioxide, carbon monoxide, ozone, sulfur dioxide, PM₁₀, and PM_2.5 and the number of hospital admissions for asthma, pneumonia, ischemic heart disease, and cerebrovascular disease from 1995 to 2002. Admissions for ischemic heart disease were associated with several sandstorm metrics, including indicators of high PM₁₀, high PM_10-2.5, and a high ratio of PM₁₀ to PM_2.5, although the lag structure of effect was not consistent among sandstorm indicators. Hospital admissions for ischemic heart disease were 16-21% higher on sandstorm days than on other days.

Despite the large body of evidence on the general population and on susceptible individuals, the health effects of PM in relatively healthy, active military personnel deployed in the Middle East are not well characterized. Part of the reason may be the challenges in conducting an exposure-monitoring and health-surveillance study in a military zone. Because of the differences in exposure concentrations and PM chemical composition, and because of the differences in deployed military personnel compared to the general population, extrapolating results directly from population-based epidemiology studies conducted in the United States and Europe to populations in the Middle East may not provide appropriate

estimates of health effects. In addition, because each military deployment is unique, the environmental exposures and health risks may vary (IOM 2006, 2008), and this could hinder the comparison of exposures and health effects in deployed personnel among different studies, especially if they are under stress.

Deployment of forces in hostile or unfamiliar environments is inherently risky because of conditions imposed by the military mission. Each deployment involves an array of military and nonmilitary threats, known and unknown, and mission objectives dictate that the threats be dealt with as they arise. Many activities carried out in such an environment are not routine; tasks must be accomplished with the means at hand despite potential dangers and in a setting where time and attention are at a premium (NRC 2000).

Conducting exposure-assessment research and health-surveillance studies presents additional obstacles, given that they are not essential to the military mission. Obstacles include limitations on the personnel available to conduct and maintain exposure assessment and surveillance, inasmuch as a brigade has only two persons responsible for the health of about 2,000 soldiers (Sheehy 2009); frequent movement of troops, which makes health-surveillance followup challenging; difficulty in acquiring Institutional Review Board approval from the military to conduct health surveillance in the field (Baird 2009); and exposure of troops to multiple sources (dust storms, vehicle emissions, and emissions from burn pits) and to confounding factors (such as smoking) that may not be well characterized. Other challenges that make exposure assessment difficult include the extreme and variable temperatures that may cause malfunctions of electronic sampling equipment; lack of access to electricity to operate PM samplers, which makes it necessary to use batteries; the increased PM concentrations that can overload the samplers and necessitate special sampler preparation (for example, Demokritou et al. 2004); and less than optimal settings for locating the samplers.

Military personnel—especially those deployed to war zones—are considered “healthy adults” because of their age and the military’s physical and health requirements. However, a small percentage of deployed people will have conditions that put them at greater risk for health effects from exposure to PM. For example, despite a screening program and regulations that prohibit enrollment of asthmatics, it is estimated that—because of waivers, late onset of asthma, and misdiagnosis—3-5% of military personnel have asthma (DeKoning 2006; Smith et al. 2009) compared with about 7% of the general population who have asthma and about 13% who have ever been diagnosed with asthma (CDC 2008). Moreover, some people may have underlying conditions that are not diagnosed (for example, respiratory and cardiovascular disease).

Military personnel may also have risk factors that can exacerbate the effects of PM exposure (for example, smoking and stress), but no studies have evaluated the joint influence of these risk factors and exposure to air pollution on health effects in the military. A number of studies in children have examined the association. Understanding the influence of these risk factors in children might help to elucidate factors that affect the health of military personnel. For example, Shankardass et al. (2009) found that children living in stressful house-

holds were more susceptible to the effects of traffic-related air-pollutant emissions and in utero tobacco-smoke exposure than those in less stressful ones. Clougherty et al. (2007) found that a 4.3-ppb increase in nitrogen dioxide exposure increased the risk of asthma (odds ratio, 1.63; 95% confidence interval, 1.14-2.33) solely in children who had above-median exposure to violence. Other researchers have reported similar findings in children (Lee et al. 2006; E. Chen et al. 2008).

There are few studies of the association between concentrations of PM and health effects in deployed personnel in the Middle East. Petruccelli et al. (1999) studied health-related complaints of soldiers who lived and worked in Kuwait during the oil-well fires in 1991. They used self-administered questionnaires after the soldiers’ return and found that deployment to Kuwait was associated with an increased incidence of eye and upper respiratory tract irritation, shortness of breath, cough, rashes, and fatigue. Those symptoms were reported more often by soldiers who perceived oil-fire smoke, pollution, heat exhaustion, flying insects, and sunburn as posing substantial problems. Lange et al. (2002) examined the relationships between respiratory symptoms in military personnel 5 years after deployment to the Persian Gulf War and self-reported and modeled exposures to smoke from oil fires. Self-reported symptoms of asthma and bronchitis increased with the number of days exposed to the oil fires, but there was no correlation of reported symptoms with modeled exposures. Cowan et al. (2002) conducted a case-control study of asthma in Army Gulf War veterans and modeled exposure to oil-well fire smoke. Two modeled exposure estimates were used: cumulative smoke exposure and the number of days subjects were exposed at 65 μg/m³ or greater. They found a significant association between asthma and both estimates of exposure, and a dose-response relationship was observed for both measures.

Other studies have investigated respiratory symptoms in general in military personnel deployed to the Middle East. Sanders et al. (2005) conducted a survey to assess the prevalence of common ailments in U.S. military personnel deployed to Iraq and Afghanistan during 2003-2004, and the impact of those ailments on the military missions. Mission impact was determined by a questionnaire in which a person reported missing a patrol or being grounded from flying. They found that 69.1% of those surveyed reported respiratory illnesses; in 17% of these cases, medical care was sought. Another example is the Millennium Cohort Study, which is a 21-year longitudinal study by the U.S. Department of Defense (DOD) to evaluate risk factors related to military service that may be associated with long-term health outcomes. Participants were U.S. military personnel who were serving on active duty or in the reserves or National Guard in October 2000 (Smith et al. 2007). A recent study of this cohort investigated newly reported respiratory symptoms and conditions among military personnel deployed to Iraq and Afghanistan (Smith et al. 2009). Data from baseline and followup questionnaires found that new-onset respiratory symptoms were reported by 14% of deployed soldiers compared to 10% of nondeployed soldiers, while rates of chronic bronchitis or emphysema and asthma were similar

between the deployed and nondeployed groups. In addition, increased risk of symptoms was associated with deployments on land compared to sea-based deployments. The Millennium Cohort Study is examining PM exposures of military personnel, but the data have not yet been published.

At the beginning of Operation Enduring Freedom (Afghanistan, 2001) and Operation Iraqi Freedom (2003), DOD initiated sampling of air, water, and soil in the Central Command Area of Operations (that is, the Middle East region, including Egypt and Central Asia) to characterize the deployment environment. The most common type of ambient air sample collected was PM.

In 2005, the assistant secretary of defense for health affairs chartered the Joint Particulate Matter Working Group (DOD-NIOSH 2005) to identify health issues that were potentially associated with exposure to PM. A workshop was held at the National Institute for Occupational Safety and Health to review sampling results, potential health effects, and knowledge gaps pertaining to PM exposure of military personnel in the Middle East. Data-related needs identified in the symposium included enhanced PM surveillance, routine predeployment and postdeployment health evaluations, improved disease and nonbattle-injury data, epidemiologic study of potential adverse effects of exposures to PM in the Middle East areas of operation, and assessment of the toxicity of the PM to which deployed personnel are exposed.

In response to an identified data need, the Enhanced Particulate Matter Surveillance Program (EPMSP) was implemented by the U.S. Army Center for Health Promotion and Preventive Medicine and a report was prepared by Engelbrecht et al. (2008) that included the design, analysis, and results of the EPMSP (see Appendix D). The report presents data on PM concentrations (that is, PM_2.5, PM₁₀, and TSP), chemical composition, and bulk soil samples at 15 locations in the Middle East. The results of the EPMSP are “available to the [U.S.] Department of Defense’s occupational and health physicians, as well as environmental health professionals, to assist them in assessing potential human health risks from exposure to ambient particulate matter at their Middle East military base. In addition, information on dust allows for an assessment of its potential harmful effects on military equipment” (Engelbrecht et al. 2009).

This report constitutes an independent assessment of the DOD EPMSP report (Engelbrecht et al. 2008). The U.S. Army asked the National Research Council to review sampling and analytic approaches and potential acute and chronic health implications on the basis of information presented by Engelbrecht et al. The National Research Council was also asked to consider the epidemi-

ologic, health-surveillance, and toxicologic data collected by DOD (Abraham 2009; Ross 2009; Stockelman 2009), assess the potential health implications for deployed personnel, and make recommendations for reducing or better characterizing health risks, including improving epidemiologic investigations. In response, the National Research Council convened the committee for Review of the DOD’s Enhanced Particulate Matter Surveillance Program Report, which prepared the present report.

The committee conducted its evaluation of the EPMSP report by reviewing the sampling methodology (Chapter 2) and the analytic approaches and data presented (Chapter 3) by Engelbrecht et al. Chapter 4 moves beyond the results presented by Engelbrecht et al. to evaluate health and toxicology data presented at the committee’s first meeting (see Appendix C).¹ In this chapter, the committee addresses information needed to characterize health risks to deployed personnel. Chapter 5 presents the committee’s conclusions and recommendations and looks toward designing studies to improve understanding of the health implications of PM for personnel deployed to the Middle East.

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