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OCR for page 34
4
Safe Disposal of Infectious
Laboratory Waste
A. INTRODUCTION
Human activities produce biological waste in the
form of human excrete or other discarded materials,
much of which may contain infectious microorgan-
isms. Such waste, if untreated, has varying degrees
of potential to cause disease. Existing methods of
sanitation have served effectively to protect the pub-
lic's health from any disease associated with biologi-
cal waste. Our understanding of the conditions re-
quired to prevent the transmission of disease has
allowed the development of simple, yet highly effec-
tive management techniques for handling biologi-
cally contaminated waste. A brief review of some of
the conventional measures used to protect the pub-
lic's health follows.
Historically, human excrete have been linked to
outbreaks of disease such as dysentery, poliomyeli-
tis, typhoid, and cholera. Such waste may contain
high concentrations of pathogens that can contami-
nate food and water supplies. To minimize the op-
portunity for such cross-contamination, several fun-
damental principles of sanitation are applied. The
first principle consists of providing a physical bar-
rier. Sanitary sewer systems, which consist of pipes
and pumps to convey pathogen-laden sewage to a
treatment plant, effectively provide such a barrier.
Once the waste reaches the sewage treatment plant,
other mechanisms help to reduce the disease-causing
potential of the material.
The treatment of sewage usually consists of bio-
logical degradation of the organic material. The
physical and biochemical conditions that are optimal
for such degradation are often hostile to the survival
of many human pathogens. The end result is a sig
nif~cant reduction in the numbers of viable patho
· · . . . .
gene microorganisms rema~nmg In t he treater waste.
After the organic load in the sewage has been
degraded to the desired level, the effluent from He
sewage treatment plant is usually subjected to a final
disinfection step before being released into the envi-
ronment. This step is accomplished by chlorination/
dechlorination, exposure to ultraviolet light, ozona-
tion, or some other procedure. The process ensures
that the concentration of pathogens in the effluent is
reduced to an acceptable level.
Like sewage, much solid waste or refuse pro-
duced by man is contaminated with biological agents
capable of causing infection in man [391, and many
of the same control mechanisms apply. For both
storage and transport for disposal, the barrier system
is again particularly important for the protection of
individuals who must handle the waste. The plastic
refuse storage bag, the dumpster, and the enclosed
refuse-handling vehicle all provide barriers to mini-
mize the potential of the waste to contaminate the en-
vironment.
Most solid waste is either disposed of directly in
sanitary landfills or treated first by incineration to
reduce its volume. Sanitary landfilling is a con-
trolled disposal method designed largely to protect
the public's health and the environment and conse-
quently has largely replaced the open dump. Besides
producing smoke and odors, open dumps provide
ideal habitats for the propagation of disease-carrying
vectors of concern to man, such as rats, flies, and
mosquitoes. The sanitary landfill eliminates this
habitat by compacting the waste and providing a
daily earth cover, also compacted, to seal off the
waste from the general environment. The earth above
34
OCR for page 35
SAFE DISPOSAL OF INFECTIOUS LABORATORY WASTE
and below is the barrier. Because the conditions of
biodegradation within the landfill are hostile to many
human pathogens, their numbers decrease with time
[39,1161.
It is recognized that sanitary landfills may pro-
duce liquid leachate that can carry viable microor-
ganisms to the earth underlying the landfall. As a
leachate percolates through the earth, remaining pa-
thogenic microorganisms are reduced further in con-
centration by hostile environmental factors and by
soil filtration. This principle is used to advantage in
the leach fields of home septic systems [871.
Incineration of municipal waste is done primarily
to reduce the volume of the waste. Because munici-
pal waste is generated by both healthy and sick indi-
viduals, it contains the same array of human patho-
gens as those associated with hospital waste. A1-
though it is not their primary goal, well-designed and
well-operated municipal incinerators can provide ef-
fective destruction of pathogens in the same way that
a hospital incinerator does. Municipal incinerators
often operate at higher temperatures and with longer
gas retention times, thereby enhancing their effec-
tiveness for the destruction of pathogens.
In summary, the application of long-standing prin-
ciples of sanitation is effective in controlling the
threat to the general public's health associated with
biological waste. In general, extraordinary pathogen
control measures have not been shown to be neces-
sary except where the physical nature of the waste
(e.g., contaminated "sharps" that penetrate barriers)
presents problems directly to the waste handlers, or
the waste itself has an exceptional bioload in a mo-
bile form such as a liquid culture of a pathogenic
agent. In such cases special waste packaging may be
needed, or on-site decontamination applied, to re-
duce the concentration of pathogens to acceptable
levels.
B. INFECTIOUS POTENTIAL OF
LABORATORY WASTE
For laboratory waste to cause infection, six essen-
tial factors must be present. These factors are as fol-
lows:
1. The presence of an infectious agent that is ca-
pable of invading and multiplying within a human
host.
35
2. An environment for the infectious agent that
functions as a reservoir, allowing it to survive and,
perhaps, to multiply.
3. A mechanism for the agent to escape from the
reservoir.
4. A mode of transmission from the reservoir to
a human host.
5. A means for the agent to invade, penetrate, or
enter a human host.
6. A human host that is susceptible to infection
by the agent.
The absence of any one of these factors will interrupt
the infectious process and human disease will not
ensue.
An understanding of these factors is necessary for
assessing public health risks and the risk of occupa-
tionally acquired illness that may be associated with
the management of infectious waste. Infectious waste
implies the presence of viable pathogenic microor-
ganisms in sufficient concentration to infect a sus-
ceptible human host. There is no risk of disease
when the concentration of pathogenic organisms is
below that which is capable of invading the host and
multiplying within it. The source of the infectious
waste may be a patient in a health care facility, an
experimental animal in an infectious disease vivar-
ium, or the culture medium used for the propagation
of an infectious agent. The processes that generate
the waste provide the means by which the infectious
agent escapes from the reservoir. Thus the agent,
reservoir, and means of escape will always be pres-
ent in institutions that generate infectious waste.
Treatment and disposal strategies that protect the
public's health and prevent occupationally associ-
ated infection will therefore be necessary to block
transmission of the agent and exposure of a suscep-
tible host.
1. Risks to the General Public's Health
Risks to the general public's health can be associ-
ated only with indirect modes of transmission, be-
cause the public is not directly exposed to the institu-
tional reservoirs or the infectious waste generated by
them. For indirect transmission to occur, the infec-
tious agent must be capable of survival outside of the
reservoir for an extended period of time. There also
must be an opportunity for a susceptible host to be
OCR for page 36
36
exposed to the agent. Modern sanitation practice, as
discussed in the introduction, minimizes the occur-
rence of such events. A properly functioning com-
munity sanitary landfill, solid waste incinerator, or
municipal sewage treatment facility provides ade-
quate containment and treatment for infectious waste,
even when the waste is introduced without prior treat-
ment.
2. Occupational Risks
Unlike the general public, workers who generate,
handle, and process infectious waste have the poten-
tial for direct exposure to infectious agents. Expo-
sures can occur through direct inoculation, such as
when a worker is cut accidentally by a piece of
contaminated glass, or through inhalation when the
handling process generates aerosols. Occupationally
acquired illness associated with the handling of in-
fectious waste has been reported [591. Protection
against occupationally acquired illness is achieved
through appropriate waste handling and treatment
methods, which either contain the waste or inactivate
the infectious agent. This chapter provides guidance
to assist institutions and generators in establishing
prudent practices for the management of infectious
waste.
C. CHARACTERISTICS OF INFECTIOUS
LABORATORY WASTE
Infectious laboratory waste is characterized prin-
cipally as waste that contains microorganisms ca-
pable of causing infection in a healthy, susceptible
host. Hospitals, health care facilities, medical re-
search institutions, and industrial facilities can gen-
erate infectious laboratory waste. Categories of op-
eration that produce infectious waste include the fol-
lowing:
· operations that involve the processing and
analysis of specimens for diagnosis, separation or
purification of cells or substances from human
blood and body fluids, and in vitro and in vivo
methods for the propagation of pathogenic micro-
organisms;
· medical operations in which invasive proce-
dures are likely to result in waste contaminated
with blood and body fluids from an individual
who harbors an infectious agent;
BIOSAFETY IN THE LABORATORY
· veterinary operations involving the study of
zoonotic disease in which infected animal carcasses
and tissues, contaminated fomites such as dispos-
able instruments and supplies, and contaminated
bedding materials are produced;
· anatomical pathology services where work-
ers process specimens from individuals either
known to harbor, or who are at an increased risk
of harboring, an infectious agent;
· diagnostic, research, and industrial opera-
tions that involve the collection and processing of
bulk quantities of human blood, blood deriva-
tives, or body fluids; and
· the production of biological products in
which pathogenic microorganisms are used, such
.
as vacclnese
Biological waste with objectionable or putrescent
characteristics, containing viable microorganisms that
are either not known to be hazardous to humans or
are minimally potentially hazardous, is not consid-
ered infectious laboratory waste. Examples include
tissues or medical waste generated from the care of
individuals who have not contracted an infectious
disease; solid waste including such items as soiled
diapers, animal bedding materials or pet litter, ani-
mal carcasses, and garbage from food processing
plants and eating establishments. Objectionable
nonhazardous medical waste is typically generated
in extended care facilities and ambulatory health care
services. Adherence to good personal hygiene and
prudent sanitation practice affords adequate protec-
tion to individuals involved in the handling and dis-
posal of this type of waste.
D. RESPONSIBILITY FOR THE SAFE
HANDLING AND DISPOSAL OF
INFECTIOUS WASTE
The primary responsibility for the safe handling
and disposal of infectious waste resides with the
generator of the waste. This responsibility extends
to the ultimate point of disposal even when there are
other parties involved in handling the waste. The
generator should conduct inspections or take other
measures to ensure that the waste is being handled
and disposed of properly, even though management
of infectious waste is also the concern of waste haul-
ers and treatment facility operators. In addition,
OCR for page 37
SAFE DISPOSAL OF INFECTIOUS LABORATORY WASTE
there may be federal, state, or local regulations con-
trolling medical waste disposal and recordkeeping
that must be observed.
The major problem associated with infectious
waste is the potential for occupational exposure. The
disposal of infectious waste should, therefore, be
performed in an effective manner that minimizes the
potential for exposure of those who, by virtue of their
employment, must handle the material.
It is incumbent upon the scientific community to
educate the general public about the effectiveness of
current sanitation practices in protecting the public's
health, and to direct legislators' attention to the prob-
lems of the occupational hazards associated with the
handling of infectious waste.
1. Generators of Infectious Waste
The initial recognition of a potential hazard should
set in motion all of the mechanisms from source to
final disposal. Recognition is made most effectively
by the generator of the waste. The responsibility for
proper handling, treatment, and disposal of infec-
tious waste materials resides with all those who know-
ingly come in contact with these materials. How-
ever, the major responsibility for proper handling
belongs to the initial generator of potentially hazard-
ous materials, because such waste material should be
identified and segregated according to its degree of
potential hazard. Once the material has been identi-
f~ed as infectious waste, proper packaging and con-
tainment should be ensured until decontamination or
inactivation can be accomplished.
The most senior official of the facility generating
the waste has the responsibility for the development
of a waste management program. Such a program
should ensure proper containment of infectious waste
and the development and implementation of appro-
priate methods for the efficacious decontamination
of this waste. It is incumbent upon management to
ensure that proper operational controls of selected
treatment methods are maintained.
No waste management program is functional un-
less all appropriate personnel are cognizant of the
aims of the program and trained in the procedures for
handling the waste. Management should provide
resources and ensure that training programs are de-
veloped and implemented. Training should be a
continuing process.
37
2. Haulers and Waste Treatment Facilities
Infectious waste is often decontaminated at the
generating facility prior to its transport to a disposal
site. Decontamination protects the waste hauler from
the risk of infection.
In those instances where the waste hauling com-
pany transports untreated infectious waste to a treat-
ment and disposal site, adequate physical contain-
ment measures should be provided to minimize oc-
cupational exposure. The processing of infectious
waste by a treatment facility requires the same strin-
gent attention to detail that is required of the genera-
tor treating its own waste. The treatment company
has the responsibility for ensuring that all procedures
are adequate and that all systems are functioning
correctly. Both hauling and treatment companies
should ensure that all of their personnel are made
aware of the potential hazards of exposure. Person-
nel should be properly trained in all of the pertinent
aspects of the containment, the handling, and the
treatment of infectious waste. Contingency plans
should be developed to handle accidents that may
occur.
E. WASTE HANDLING AND
TREATMENT METHODS
The prudent management of infectious laboratory
waste requires the development of site-specif~c plans.
Procedures developed by personnel within a facility
will be appropriate for the specific needs of that
facility and may gain a higher level of acceptance
than will procedures imposed from outside sources.
The process of developing a waste management plan
is, in itself, acknowledgment of the need to accept
responsibility for laboratory waste.
1. Basic Principles
Persons who generate infectious laboratory waste
are responsible for preparing the waste so that poten-
tial occupational exposures and environmental con-
t~nination are minimized. Infectious waste needs to
be segregated by the generator from other waste
streams. This process will obviate the need for deci-
sion-making by support services personnel. The waste
can then be treated on-site to reduce the concentra-
lion of the pathogen to an acceptable level (decon
OCR for page 38
38
lamination), or packaged in a way to prevent subse-
quent exposure of other persons having to handle the
waste prior to terminal bmaunent. Packages of infec-
tious waste need to be identified so that the potential
hazard clearly can be recognized and understood by
others. The universal biohazard symbol is used for
this purpose.
2. Containmen
A variety of packaging items for containment and
transport of infectious waste are available. Infec-
tious waste containers serve as primary barriers to
protect the worker and to minimize the chance of
environmental contamination Figure 4.1~. Typically,
these containers are made from leak-resistant paper
or cardboard, stainless steel, or temperature-resistant
polymers. The nature and volume of the waste, the
terminal treatment method, and their costs are princi-
pal factors to consider in the selection of the mode of
packaging.
: :~ ~ if: ~ ~:~ ~ ~ ::~:~;~;~._
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BIOS0ETY IN THE ORATORY
Solid waste can be packaged safely in sturdy bags
or boxes. Flat trays with sealable lids are suitable for
containing pipettes and other laboratory supplies
during decontamination. Built liquids may be col-
lected in leak-proof containers, decontaminated, and
then safely discharged into the sewer system. Rigid,
puncture-resistant, sealable containers are necessary
for packaging "sharps," e.g., broken glass, brittle
plasticware, needles, and scalpel blades. Wet waste
should be packaged with sufficient absorbent materi-
als to contain residual liquids and to minimize leak-
age. In packaging wet materials for transport, it is
prudent to double-bag the waste, sealing each bag
independently. Heavy waste such as anatomical speci-
mens, animal bedding, and laboratory specimens need
to be placed in rigid containers. Care must be taken
that the weight of the waste load does not exceed the
burst strength of the container.
The physical properties of the container should
be compatible with the treatment process. Waste
placed in stainless steel pans, waxed-lined paper bags,
FIGURE 4.1 Biohazardous waste should be segregated from over types of waste prior to its disposal. Courtesy, National
Institutes of Healths
OCR for page 39
SAFE DISPOSAL OF INFECTIOUS LABORATORY WASTE
tempered glass, and heat-resistant plastics can all be
safely processed in an autoclave. Metal containers
have been shown to enhance the transfer of heat to
the waste load during autoclaving, whereas contain-
ers made of plastic retard steam penetration. Pro
cessing smaller waste loads and extending the treat-
ment period can compensate for this feature of plastic
containers.
Most chemical disinfectants have no appreciable
effect on high-strength plastics at room temperature,
but may be corrosive to metals. Liquid infectious
waste often is stored in plastic carboys designed for
chemical disinfection. Metal receptacles can be auto-
claved and recycled but are not suitable for incinera-
tion. Ideally, waste should be packaged in dispos-
able receptacles that minimize handling of the waste
and are suitable for the waste stream treatment
method. Cleaning containers that are to be reused is
labor intensive and increases the risk of occupational
injuries and exposures to biohazards.
3. Personal Protection
The most important precautions for all personnel
handling infectious waste are the wearing of protec-
tive gloves and frequent handwashing. Gloves and a
laboratory coat are recommended for all activities
involving manipulations of contaminated items.
Gloves and clothing should be changed when soiled
or damaged. Thorough handwashing is recommended
after working with infectious materials. Scavenging
through waste, as well as eating, drinking, and smok-
ing while working with waste, must be prohibited.
The type of laboratory activity will determine if
there is a need for additional protective measures.
Laboratory activities with a high probability of con-
tamination caused by spills of infectious fluids, or
the production of droplets, should be performed on
plastic-backed absorbent bench paper. Workers who
process infectious waste in an autoclave should wear
a rubber apron, sturdy shoes, asbestos-free heat-
resistant gloves, and a face shield, to protect against
accidents that may occur while loading or unloading
the autoclave.
4. Chemical Decontamination
Liquid and gaseous chemicals are used routinely
for decontaminating infectious waste. Table 4.1
summarizes use parameters and applications for
39
chemical decontamination of specific types of fre-
quently generated infectious waste from laboratories
[1401. Some examples of these applications are as
follows:
· Use of an intermediate decontamination step
during the storage or transport of waste, e.g., the
addition of liquid chlorine bleach, iodophors, or phe-
nolic disinfectants to pipette discard pans at work
stations. The concentration of decontaminant for
this use should be such that the addition of liquid
waste will not interfere with its effectiveness.
· Gaseous decontamination of HEPA fetters in
biological safety cabinets. This procedure should be
carried out prior to removal of the filter for replace-
ment or prior to repairing the cabinet. Decontamina-
tion is usually carried out with formaldehyde sub-
limed by heat from pamformaldehyde flakes in the
presence of high humidity. The cabinet must be
sealed with plastic sheets and tape prior to initiating
decontamination. Human contact with the formalde-
hyde should be prevented because of the highly irn-
tating, toxic, and possibly carcinogenic properties of
the gas (the OSHA limit for permissible exposure is
2 ppm). A detailed description of the method is
available [95].
· Decontamination of large items of equipment
that are to be removed from the laboratory for repair
or discard. Care should be taken to avoid corrosion
of sensitive parts if the equipment is to be reused
rather than discarded. A disinfectant that has low
corrosive properties and has been proven to be effec-
tive against the specific microorganism should be
used for this purpose.
· Treatment of mixed hazardous waste such as
combinations of infectious agents and radioisotopes.
After an appropriate assessment of the waste, it may
be prudent to use chemically compatible decontami-
nants to avoid the release of potentially hazardous
emissions. See the section on mixed waste (Chapter
4, Section F. Part 1) for a more detailed discussion of
such problems.
5. Steam Autoclaving
Steam autoclaving usually is considered to be the
method of choice for decontaminating cultures, labo
ratory glassware, pipettes, syringes, or other small
items known to be contaminated with infectious
agents. Location of the autoclave within the labora
OCR for page 40
40
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OCR for page 41
SAFE DISPOSAL OF INFECTIOUS LABORATORY WASTE
tory minimizes storage and transport problems. It
provides a technically proved treatment method for
rendering infectious material safe. Autoclaved waste
can be disposed of as general waste.
Certain waste materials are difficult to decon-
taminate in the autoclave because they insulate and
protect the cont~ninating organisms from heat and
steam penetration. Examples include animal car-
casses, human body parts, and large volumes of con-
taminated clothing. The preferred method for decon-
tamination of animal remains and human body parts
is incineration. Routine laundering is appropriate for
clothing contaminated with all but the most haz-
ardous infectious agents. Autoclaving is not the re-
commended method for decontaminating very large
volumes of waste because the time required for pro-
cessing is too long, and the chamber size is usually
too small. The lack of volume reduction and the
failure of the autoclave process to render body parts
unrecognizable are also limitations to this process.
Operational considerations based on specific load
conditions are very important to ensure adequate
decontamination in autoclaves. Most laboratories
have gravity displacement autoclaves, which operate
at 121°C (15 lbs/in2of pressure). Because of the high
levels of organic matter normally associated with
infectious waste, these types of autoclaves should be
operated for a minimum of 60 minutes. Some labo-
ratories may have vacuum-~e autoclaves, which
operate at 132°C (27 lbsfin2 of pressure). It is recom-
mended that these autoclaves be operated for a mini-
mum of 10 minutes. The shorter time period for this
type of autoclave is due to the higher temperatures
and pressures attainable with the vacuum cycle and
the more effective penetration of steam.
It may be desirable to add water to a load of waste
to be decontaminated in an autoclave to facilitate
steam formation and penetration, as well as to avoid
the collection of residues on reusable items that may
be difficult to remove in subsequent cleaning pro-
cesses. Caution is essential while adding water to a
load, to minimize the potential for aerosolizing in-
fectious agents in the waste. Drain lines from steam
autoclaves can be connected to the sanitary sewer
except for those installed in maximum containment
laboratories (Biosafety Level 4~.
When loads contain both reusable and disposable
items, the material should be separated to prevent
melted plastic from encapsulating items to be reused.
41
6. Incineration
Incineration is the method of choice for treating
large volumes of infectious waste, animal carcasses,
and contaminated bedding materials. Because incin-
erators usually are located some distance from the
laboratory, additional precautions for handling and
packaging of infectious waste are necessary.
Incinerators require approval and permits from
local and state pollution control authorities. Although
the initial capital costs and maintenance costs are
high, incineration offers many advantages as a method
for the treatment of infectious waste [16,491. Incin-
eration significantly reduces waste volume and pro-
duces an unobjectionable end-product, ash. Proper
design and operation can provide for energy (heat)
recovery, making the operation more economical [251.
Although specific operating standards have not
been set for the incineration of infectious or patho-
logical waste, the principles of effective combustion
are well understood. Waste and the hot gaseous
products of its volatilization should be retained in the
combustion chambers) for a long enough time and
at a high enough temperature to allow for mixing
(turbulence) with excess oxygen, so that the combus-
tion reactions can go to completion. A deficiency in
any one or more of these critical combustion parame-
ters can result in smoke or odor production, exces-
sive emissions of harmful gaseous by products, and
the discharge of incompletely burned waste residue.
Many modern incinerators achieve the proper
conditions for complete and effective combustion by
providing secondary combustion chambers or zones
with burners to ensure that adequate conditions for
time, temperature, and mixing are achieved. Primary
combustion temperatures of at least 1600-F win good
mixing and a gaseous retention time of about 2 sec-
onds should provide for good burnout for the waste
described in this chapter. All pathogens and protein-
aceous materials are denatured at temperatures well
below that just cited [491.
Complete combustion also is dependent on cor-
rect operation of the equipment. The operator of Be
incinerator should be careful to avoid overfeeding
with waste materials. Too much raw waste in the
primary combustion chamber can overwhelm the
combustion zones with more volatile products than
the equipment is designed to handle within a fixed
gas retention time. The result of overfeeding will be
OCR for page 42
42
smoke and odors. Overfeeding an incinerator also
can result in the bottom ash being moved though the
primary chamber too quickly, and consequently being
discharged before complete burnout takes place.
Another condition that can result in incomplete
burnout of the bottom ash (uncombusted feed mate-
rial) is the lack of tumbling of the solid waste feed
pile in the primary chamber. This is a common
condition developing in top-fed incinerators where
waste continually is fed directly on top of the exist-
ing pile of previously loaded waste materials. In this
situation an outer layer of insulating ash can form
that retards combustion of the contents in the center
of the pile. To achieve complete residue burnout,
provisions should be made to agitate or break up the
pile periodically. This can be done mechanically
with an oxygen pulse or manually with a rake.
In selecting a new incinerator for a facility, it is
critical that the actual waste stream to be treated be
characterized. Too often in the past the term `'patho-
logical waste" has been used to determine the size of
an incinerator. True pathological waste consists of
animal tissue that is quite wet and has an approxi-
mate heat content of 1000 BTU/lb (555.6 kcal/kg).
Infectious waste incinerators should burn a wide va-
riety of materials including significant amounts of
paper and plastics as well as pathological waste. The
effective heat content of the actual waste mix usually
will be well above 1000 BTU/lb. Only by knowing
the specific composition of the facility's waste stream
can a vendor properly size the unit.
In summary, safe, effective incineration can be
achieved by (1) proper equipment design; (2) provi-
sion for the time, temperature, turbulence, and air
required for complete oxidation; and (3) careful feed-
ing of the unit. To assist the laboratory manager in
the selection of equipment, a consultant knowledge-
able in the field of incineration should be retained to
help develop a site-specif~c procurement specif~ca-
tion [491.
7. Validation of Decontamination Methods
Sterility testing or testing for survival of an indi-
cator microorganism is neither applicable nor practi-
cal to verify the adequacy of the treatment of infec-
tious waste, since sterility is not an objective of
decontamination methods, and indicator microorgan-
isms do not simulate typical waste load composition.
Rather, precise reproduction of each of the condi
BIOSAFETY IN THE LABORATORY
lions (operational parameters) prescribed for the dif-
ferent treatment methods should be relied upon to
ensure adequate treatment each time waste is pro
cessed. This reliance, however, is justifiable only if
all of the measuring devices used to monitor the
treatment process (e.g., thermometers, pressure
gauges, and timing mechanisms) are functioning
properly. It is imperative that the accuracy of these
measuring devices be certified independently by the
user, after the equipment is first installed and before
any waste is treated, and again thereafter at regularly
scheduled intervals (at least annually). This process
should be repeated after maintenance work or repairs
are carried out, and if the equipment is relocated.
Each of the different treatment methods for infec-
tious laboratory waste requires a different set of con-
ditions to be effective. Effective autoclaving is
dependent upon time, temperature, and steam pene-
tration, whereas effective incineration is dependent
upon time, temperature, and turbulence. Chemical
decontamination is dependent upon several parame-
ters, including selection of an effective chemical,
contact time, concentration, and the presence of or-
ganic materials or other interfering substances. Op-
erator controls include such matters as procedures
for packaging the waste, placement of the load, feed
rate, and-perhaps most important-the keeping of
an accurate record of the operational parameters
achieved for each load processed. Detailed informa-
tion regarding the principles of efficacious treatment
is available [48,49,52,75,111,1401.
Chemical indicators are of limited value in veri-
fying the decontamination of infectious waste.
Chemical indicator inks printed on waste packaging
materials intended for autoclaving provide a color
change that serves only to distinguish treated waste
from waste requiring treatment i.e., failure of an
indicator to change to its signal color after the proc-
ess demonstrates immediately that the equipment has
malfunctioned.
F. INFECTIOUS WASTE REQUIRING
SPECIAL CONSIDERATION
1. Milled Waste
Mixed waste consists of materials that exhibit
multiple hazardous properties, such as infectivity
radioactivity, and chemical toxicity. Frequently, some
of the components are strictly regulated by environ
OCR for page 43
SAFE DISPOSAL OF INFERIORS "BO~TORY WASTE
mental protection and transportation agencies of the
local, state, and federal governments. However, treat-
ment and disposal strategies for mixed waste gener-
ally are not addressed by most regulatory agencies.
One difficulty, in part due to conflicting regulations,
is that mixed waste frequently is not accepted at
disposal facilities operating under permits issued by
the Environmental Protection Agency (EPA) or li-
censed by the Nuclear Regulatory Commission
(NRC). Waste managers should anticipate that dis-
posal problems will occur. Also, the concern of the
public regarding hazardous waste disposal, in gen-
eral, is likely to influence the development of more
restrictive mandates for handling mixed waste. The
uncertainty that exists with regard to the treatment
and disposal of mixed waste emphasizes the impor-
tance of the prudent practice of implementing waste
minimization and separation strategies for the types
of operations that generate mixed waste.
Waste minimization should be attempted at sev-
eral levels to address effectively the problem of mixed
waste. Researchers should be encouraged to plan
experiments and select reagents that minimize the
production of mixed waste. Experimental design
may be modified such that the wastes are generated
separately and in minimal volumes. Microscale tech-
niques are now available for most experimental pro-
cedures. When feasible, substitution of less hazard-
ous materials should be considered. Appropriate
waste containers should be made available at the
work site to ensure convenient and correct segrega-
tion and labeling of the waste.
Waste managers commonly have to make a deci-
sion about the method to be used for the treatment
and disposal of mixed waste. If unusual disposal
problems are anticipated by the generator of mixed
waste, the waste manager for the institution should
be informed prior to generation of the waste. Rou-
tinely, the regulated hazardous waste component takes
precedence in any treatment and disposal strategy. It
is important to recognize, however, that the most
serious hazard associated with the waste may not be
the regulated component. Placing emphasis on the
regulated component therefore may not be the safest
approach; in fact, the risks involved in the handling
of mixed waste could be exacerbated. A careful
assessment of the waste composition is required in
order to select the appropriate strategy for treating
the mixture. Thermal or chemical inactivation of the
infectious component of mixed waste is commonly
43
recommended by waste managers after assessing the
potential for toxic emission and chemical incompati-
bility. Once a strategy for handling the mixed waste
is decided upon, it is important that the infectious
component be decontaminated along with, or prior
to, final beannent and disposal.
Several factors in addition to Pose associated
with the infectious nature of the waste should be
considered in selecting an appropriate method of treat-
ment. Some of the more implant factors are the
type and volume of waste generated; other hazardous
properties of the waste (e.g., radioactivity, volatility,
flammability, chemical toxicity, and temperature
sensitivity [22,911~; the availability of validated treat-
ment methods and recommended safety precautions;
the permit and license status of the generator to treat
hazardous waste; the quantity and characteristics of
the end products after treatment; and the relevant
regulations, permits, and packaging requirements for
the disposal of the regulated hazardous materials in
the mixed waste.
When autoclaving mixed waste, precautions
should be taken to avoid the release of volatile radi-
onuclides (e.g., radioiodine) and toxic chemicals (e.g.,
mercury, solvents, and carcinogens). The potential
volatility of the mixture when subjected to the ele-
vated temperatures necessary to achieve thermal bio-
logical inactivation is therefore an important factor
in the assessment of these types of mixed waste.
Mixed waste containing conjugated tritium, techne-
tium-99, carbon-14, and other radionuclides has been
autoclaved safely at various institutions, but this
method should be approved by the radiation safety
officer of the institution. Waste containing flam-
mable or reactive chemicals should not be autoclaved.
Care should be taken to avoid contamination of the
equipment. Autoclaves used for processing radioac-
tive waste should be labeled with the universal radia-
tion symbol.
Excreta that contain radionuclides from patients
undergoing diagnostic nuclear medicine procedures
may be discharged into the sanitary sewer if the
activity levels in the sewage do not exceed license
limitations. Excreta from patients receiving che-
motherapeutic drugs may be discharged into the sani-
tary sewer, if this practice is in compliance with local
regulations. Specimens of blood and body fluids
obtained from these classes of patients often are sub-
mitted for laboratory analysis. These diagnostic speci-
mens can be discharged into the sanitary sewer un
OCR for page 44
44
ureas, or autoclaved and disposed of as general
waste.
The incineration of mixed waste is dependent
upon the regulatory requirements and permits for the
hazardous chemical or radioactive components.
Volatile metals (mercury) should not be incinerated
but may easily be treated by other methods. Waste
management strategies are hindered when the mix-
ture contains volatile metals in addition to other haz-
ardous waste components that dictate incineration as
the treatment of choice.
Treatment of all regulated waste and regulated
components of mixed waste is restricted to facilities
holding the necessary permits. At the time of this
writing, none of these facilities accepts waste con-
taining the"dioxin group" compounds (chlorinated
phenols and phenoxy acetic acids, chlorinated di-
benzo-p-dioxins, or chlorinated dibenzofurans) for
treatment or disposal. Thus, mixed waste containing
any of the dioxin group compounds is difficult to
manage. Due to the lack of permitted facilities and
the resulting requirement for long-term storage at the
producing institution, stringent waste minimization
strategies should be implemented to minimize the
generation of this type of mixed waste.
Chemical decontamination of mixed waste re-
quires an assessment prior to treatment to avoid po-
tential occupational hazards or difficult disposal prob-
lems. For example, decontamination of mixed waste
containing radioiodine with sodium hypochlorite
could result in the release of the radionuclide.
2. Human Cadavers and Other Anatomical
Waste
All anatomical waste requires special handling
and packaging due in part to its putrescent properties
at ambient temperatures. Cold storage is necessary
for nonpreserved anatomical waste to minimize odors
and leakage problems. Human body parts, bodies,
and cadavers should be disposed of by cremation,
burial, or incineration as stipulated in regulations
promulgated by the state anatomy board.
Biomedical laboratory and veterinary research
operations also generate anatomical waste such as
pathological specimens and animal carcasses. Stud-
ies of animal and human infections may generate
infectious anatomical waste. This waste may be
packaged in a durable, preferably opaque, plastic
liner that is placed in a sturdy paper fiber box or
BIOS~ETY IN THE LABORATORY
drum. As a precaution, absorbent material can be
added to contain any fluids that might be present.
Incineration is the treatment of choice for anatomical
waste derived from infected hosts. A facility with a
properly designed and operated medical waste incin-
erator can effectively treat infectious anatomical 1
ratory and veterinary waste for disposal.
3. Animal Bedding Materials
Soiled animal bedding material also becomes
malodorous when stored at ambient temperatures for
extended periods of time. Adherence to good sanita-
tion practices can minimize potential problems.
Bedding materials obtained from healthy laboratory
animals are managed as solid waste and disposed in a
sanit~y landfill. Institutional or local requirements
may apply to the management and disposal of animal
waste containing excrete. Decontamination of soiled
bedding materials from healthy animals is not indi-
cated, although containment precautions should be
instituted to minimize the production of allergenic
aerosols.
Contaminated bedding materials and disposable
fomites associated with infected animals are also
examples of infectious waste. Incineration is the
decontamination treatment recommended for com-
bustible, high-density waste. Incinerable small-ani-
mal cages are often used in Biosafety Level 3 facili-
ties. This practice avoids the formation of infectious
aerosols during the handling and disposal of bedding
and related waste. Autoclaves may be available on
site or in close proximity to the animal holding areas
to decontaminate bedding materials or excrete con-
tained in metal or heat-resistant plastic cages. De-
contaminated solid waste then may be managed as
general waste.
4. "Sharps"
Needles and other penetrating items such as sur-
gical blades, pipettes, broken glass, and laboratory
instrument sampling probes pose a physical hazard
to laboratory and support service personnel and, if
used to process infectious materials, may transmit
infection. All disposable "sharps" should be placed
in a prominently labeled, leak- and puncture-resis-
tent container that is consistent with the institution's
waste management plan. Sturdy corrugated fiber
boxes are used routinely for packaging broken glass
OCR for page 45
SAFE DISPOSAL OF INFECTIOUS LABORATORY WASTE
and brittle plasticware such as pipettes. The addition
of an absorbent material such as crushed cons cob to
the package will retain residual fluids and enhance
the incineration of waste containing large quantities
of plastic and glass. Hypodermic needles and surgi-
cal blades often are packaged in disposable buckets
made from a high-strength, temperature-resistant
plastic. Used disposable needles and syringes should
be placed, intact, directly into the waste receptacle
without recapping. Other safety design features may
include a sturdy handle to transport the waste safely,
45
a restricted opening with a self-activating flap to
keep the waste covered while in use, and sealable
lids to contain the waste during beabnent and dis-
posal. Placing the waste receptacle in a location
convenient to the activity generating the waste (e.g.,
in animal procedure rooms, at patient's bedside, and
on the laboratory workbench) is one strategy to en-
sure proper segregation and packaging of the waste
and to minimize the risk of injury to housekeeping
personnel.
Representative terms from entire chapter:
mixed waste
