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BMBL Section VRisk Assessment
"Risk" implies the probability that harm, injury,
or disease will occur. In the context of the microbiological and biomedical laboratories,
the assessment of risk focuses primarily on the prevention of laboratory-associated
infections. When addressing laboratory activities involving infectious or potentially
infectious material, risk assessment is a critical and productive exercise. It helps to
assign the biosafety levels (facilities, equipment, and practices) that reduce the
worker's and the environment's risk of exposure to an agent to an absolute minimum. The
intent of this section is to provide guidance and to establish a framework for selecting
the appropriate biosafety level. Risk assessment can be qualitative or quantitative. In the
presence of known hazards (e.g., residual levels of formaldehyde gas after a laboratory
decontamination), quantitative assessments can be done. But in many cases, quantitative
data will be incomplete or even absent (e.g., investigation of an unknown agent or receipt
of an unlabeled sample). Types, subtypes, and variants of infectious agents involving
different or unusual vectors, the difficulty of assays to measure an agent's amplification
potential, and the unique considerations of genetic recombinants are but a few of the
challenges to the safe conduct of laboratory work. In the face of such complexity,
meaningful quantitative sampling methods are frequently unavailable. Therefore, the
process of doing a risk assessment for work with biohazardous materials cannot depend on a
prescribed algorithm. The laboratory director or principal investigator is
responsible for assessing risks in order to set the biosafety level for the work. This
should be done in close collaboration with the Institutional Biosafety Committee (and/or
other biosafety professionals as needed) to ensure compliance with established guidelines
and regulations. In performing a qualitative risk assessment, all the risk
factors are first identified and explored. There may be related information available,
such as this manual, the NIH Recombinant DNA Guidelines, the Canadian Laboratory Biosafety
Guidelines, or the WHO Biosafety Guidelines. In some cases, one must rely on other sources
of information such as field data from subject matter experts. This information is
interpreted for its tendency to raise or lower the risk of laboratory-acquired infection.(1) The challenge of risk assessment lies in those cases where
complete information on these factors is unavailable. A conservative approach is generally
advisable when insufficient information forces subjective judgement. Universal precautions
are always advisable. The factors of interest in a risk assessment include: The pathogenicity of the infectious or suspected
infectious agent, including disease incidence and severity (i.e., mild morbidity versus
high mortality, acute versus chronic disease). The more severe the potentially acquired
disease, the higher the risk. For example, staphylococcus aureus only rarely
causes a severe or life threatening disease in a laboratory situation and is relegated to
BSL-2. Viruses such as Ebola, Marburg, and Lassa fever, which cause diseases with high
mortality rates and for which there are no vaccines or treatment, are worked with at
BSL-4. However, disease severity needs to be tempered by other factors. Work with human
immunodeficiency virus (HIV) and hepatitis B virus is also done at BSL-2, although they
can cause potentially lethal disease. But they are not transmitted by the aerosol route,
the incidence of laboratory-acquired infection is extremely low for HIV, and an effective
vaccine is available for hepatitis B . The route of transmission (e.g., parenteral,
airborne, or by ingestion) of newly isolated agents may not be definitively established.
Agents that can be transmitted by the aerosol route have caused most laboratory
infections. It is wise, when planning work with a relatively uncharacterized agent with an
uncertain mode of transmission, to consider the potential for aerosol transmission.
The greater the aerosol potential, the higher the risk. Agent stability is a consideration that involves
not only aerosol infectivity (e.g., from spore-forming bacteria), but also the agent's
ability to survive over time in the environment. Factors such as desiccation, exposure to
sunlight or ultraviolet light, or exposure to chemical disinfectants must be considered. The infectious dose of the agent is another factor
to consider. Infectious dose can vary from one to hundreds of thousands of units. The
complex nature of the interaction of microorganisms and the host presents a significant
challenge even to the healthiest immunized laboratory worker, and may pose a serious risk
to those with lesser resistance. The laboratory worker's immune status is
directly related to his/her susceptibility to disease when working with an infectious
agent. The concentration (number of infectious organisms
per unit volume) will be important in determining the risk. Such a determination will
include consideration of the milieu containing the organism (e.g., solid tissue, viscous
blood or sputum, or liquid medium) and the laboratory activity planned (e.g., agent
amplification, sonication, or centrifugation). The volume of concentrated material being
handled is also important. In most instances, the risk factors increase as the working
volume of high-titered microorganisms increases, since additional handling of the
materials is often required. The origin of the potentially infectious material
is also critical in doing a risk assessment. "Origin" may refer to geographic
location (e.g., domestic or foreign); host (e.g., infected or uninfected human or animal);
or nature of source (potential zoonotic or associated with a disease outbreak). From
another perspective, this factor can also consider the potential of agents to endanger
American livestock and poultry. The availability of data from animal studies, in
the absence of human data, may provide useful information in a risk assessment.
Information about pathogenicity, infectivity, and route of transmission in animals may
provide valuable clues. Caution must always be exercised, however, in translating
infectivity data from one species of animal to another species. The established availability of an effective
prophylaxis or therapeutic intervention is another essential factor to be considered.
The most common form of prophylaxis is immunization with an effective vaccine. Risk
assessment includes determining the availability of effective immunizations. In some
instances, immunization may affect the biosafety level (e.g., the BSL-4 Junin virus
can be worked on at BSL-3 by an immunized worker). Immunization may also be passive (e.g.,
the use of serum immunoglobulin in HBV exposures). However important, immunization only
serves as an additional layer of protection beyond engineering controls, proper practices
and procedures, and the use of personal protective equipment. Occasionally, immunization
or therapeutic intervention (antibiotic or antiviral therapy) may be particularly
important in field conditions. The offer of immunizations is part of risk management. Medical surveillance ensures that the safeguards
decided upon in fact produce the expected health outcomes. Medical surveillance is part of
risk management. It may include serum banking, monitoring employee health status, and
participating in post-exposure management. Risk assessment must also include an evaluation of the experience
and skill level of at-risk personnel such as laboratorians and maintenance,
housekeeping, and animal care personnel (see Section III). Additional education may be
necessary to ensure the safety of persons working at each biosafety level. The infectious agents whose risk is evaluated often will
fall into the following discrete categories. Materials containing known infectious agents
Materials containing unknown infectious agents
Materials containing recombinant DNA molecules
Materials that may or may not contain unknown infectious agents
Animal studies
Other applications
Other Resources
References1. Knudsen, R.C. 1998. Risk Assessment for Biological Agents in the Laboratory. In J. Y. Richmond, Ph.D, R.B.P. (ed.) Rational Basis for Biocontainment: Proceedings of the Fifth National Symposium on Biosafety. American Biological Safety Association, Mundelein, IL. 2. Benenson, Abram S., Editor. Control of Communicable Diseases Manual. 16th Edition, 1995. American Public Health Association, Washington, D.C. 20005. 3. Collins, C.H. Laboratory-acquired infections, history, incidence, causes and prevention. Butterworths, and Co. Ltd. 1983. 4. Richmond, Jonathan Y., and McKinney, Robert W., Editors. Biosafety in Microbiological and Biomedical Laboratories. Public Health Service, 3rd Edition, May, 1993. 5. Sewell, David L. Laboratory Associated Infections and Biosafety. Clinical Microbiology Reviews, 8:389-405, 1995 6. Sulkin, S.E., Pike, R.M. 1949. Viral Infections contracted in the laboratory. New England J. Medicine. 241:205-213. 7. Sulkin, S.E., Pike, R.M. 1951. Survey of Laboratory acquired infections. Am J Public health 41:769-781. 8. Sullivan, J.F. Songer, J.R., Estrem, I.E. 1978. Laboratory acquired infections at the National Animal Disease Center, 1960-1975. Health Lab Sci 15: 58-64. 9. National Institutes of Health.
Guidelines for Research Involving Recombinant DNA Molecules. (Washington: GPO, 1998)
Federal Register. 59FR34496.
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