Biological Risk Assessment and Containment Levels

Biosafety Levels 1, 2, 3

The concept of "biosafety levels" (BSL) is the basis for laboratory practices designed to prevent laboratory acquired infections. The Center for Disease Control (CDC) and National Institutes of Health (NIH) identify four levels of containment. Levels are designated in ascending order, by degree of protection provided to personnel, the environment, and the community. Protection is accomplished through proper containment.

Containment is achieved by a combination of laboratory practices and techniques, safety equipment, and facility considerations as outlined by the CDC and NIH in Biosafety in Microbiological and Biomedical Laboratories (BMBL). Required containment measures for a given protocol will depend on the results of a risk assessment of the work to be done with a specific agent. Protocols for all work at Biosafety Level 2 and above must be approved by the Institutional Biosafety Committee (IBC).

The principal investigator or laboratory director is responsible for assessing risks in order to determine the necessary biosafety level practices (containment) required to perform a task with a specific organism. This should be done in close collaboration with the Institutional Biosafety Committee (IBC) and/or University Health and Safety's biosafety professionals in order to ensure compliance with established guidelines and regulations.

The CDCs Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th Edition explains the essential elements of the biosafety containment levels. 

See BMBL Section IV for elements of: 

  • Biosafety Level 1 
  • Biosafety Level 2 
  • Biosafety Level 3

Steps to Perform a Biological Risk Assessment

  1. Identify biohazardous materials to be used in research protocol.
  2. Identify the protocol's specific risk factors for exposure to the identified hazards. This includes modes of infectious transmission for the organism (inhalation, ingestion, etc.), steps in the protocol that may create an exposure risk (use of sharps, creation of aerosols, injecting animals, etc.), and the possible consequences of an accidental exposure.
  3. Review available resources for health hazards, laboratory hazards, handling procedures, and recommended precautions.
  4. From information gathered in Step 3, determine appropriate biosafety level.
  5. Identify specific exposure control measures that will be implemented to reduce each exposure risk as identified in Step 2. Incorporate these exposure control measures into written Standard Operating Procedures (SOPs).