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Biological Risk Assesment

Risk assessment is a process used to identify the hazardous characteristics of a known infectious or potentially infectious agent or material, the activities that can result in a person’s exposure to an agent, the likelihood that such exposure will cause a laboratory acquired infection (LAI), and the probable consequences of such an infection. The information identified by risk assessment will provide a guide for the selection of appropriate biosafety levels and microbiological practices, safety equipment, and facility safeguards that can prevent LAIs. There are four primary resources to assist in the risk assessment process.

The primary factors to consider in risk assessment and selection of precautions fall into two broad categories: agent hazards and laboratory procedure hazards. The agent summary statements contained in BMBL5 identify the primary agent and procedure hazards for specific pathogens and recommend precautions for their control. A review of the summary statement for a specific pathogen is the starting point for assessment of the risks of working with that agent and those for a similar agent.

The principal hazardous characteristics of an agent are: its capability to infect and cause disease in a susceptible human or animal host, its virulence as measured by the severity of disease, and the availability of preventive measures and effective treatments for the disease. The NIH Guidelines assigns human etiological agents into four risk groups on the basis of hazard. Agents are classified into four Risk Groups (RGs) according to their relative pathogenicity for healthy adult humans by the following criteria:  Risk Group 1 (RG1) agents are not associated with disease in healthy adult humans. Risk Group 2 (RG2) agents are associated with human disease which is rarely serious and for which preventive or therapeutic interventions are often available. Risk Group 3 (RG3) agents are associated with serious or lethal human disease for which preventive or therapeutic interventions may be available. Risk Group 4 (RG4) agents are likely to cause serious or lethal human disease for which preventive or therapeutic interventions are not usually available. 

See also:

The American Biological Safety Association also maintains a risk database.


The Public Health Agency of Canada maintains Pathogen Safety Data Sheets on infectious agents


BL 2 practices and containment must be followed when handling human materials that may contain bloodborne pathogens, e.g. HBV, HCV and HIV. The OSHA Bloodborne Pathogens Standard (29 CFR 1910.1030) applies to all occupational exposure to blood or other potentially infectious materials. Under the OSHA BBP Standard employers are required to develop a written Exposure Control Plan, offer employees the hepatitis B vaccination, and provide annual training. For more information on the OSHA BBP standard see the Clemson University Exposure Control Plan.


OSHA considers both primary and established human cell lines to potentially contain bloodborne pathogens unless tests have shown them to be free of BBP. Cultured cells that are known to contain or be contaminated with a biohazardous agent (e.g. bacteria or viral) are classified in the same biosafety level as the agent. All cell and organ cultures of human origin, including well established cell lines, human bodily fluids, non-human primate and mammalian cells and tissues should be handled in accordance with the OSHA Bloodborne Pathogens Standard and under Biosafety Level 2 (BL2) containment.


The end product of risk assessment is the assignment of an appropriate biosafety level (BL) for an experiment. BL’s will be discussed in detail in Chapter 4. The initial risk assessment from the preceding resources should be followed by a thorough consideration of how the agent is to be manipulated.  Factors to be considered in determining the BL include agent factors such as:  virulence, pathogenicity, infectious dose, environmental stability, route of transmission, communicability, operations, quantity, availability of vaccine or treatment, and gene product effects such as toxicity, physiological activity, and allergenicity.  Any strain that is known to be more hazardous than the parent (wild-type) strain should be considered for handling at a higher BL. Certain attenuated strains or strains that have been demonstrated to have irreversibly lost known virulence factors may qualify for a reduction of the containment level compared to the RG assigned to the parent strain.


A final assessment of risk based on these considerations is then used to set the appropriate BL for the experiment.  The containment level required might be equivalent to the RG classification of the agent or it might be raised or lowered as a result of the above considerations.  The Institutional Biosafety Committee must approve the risk assessment and the BL for recombinant DNA.



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