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Risk Groups and Biosafety Levels

Risk Groups

Biohazardous agents are classified into Risk Groups by regulating agencies such as the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH). The classification of many biohazardous agents can be found in the CDC (BMBL), the NIH (NIH Guide), or from the American Biological Safety Association (ABSA) . The risks are generically defined as follows:

Risk GroupDefinition
RG 1Well characterized agents that are not known to cause disease in healthy adults, or agents that present a minimal risk to the environment.
RG 2Agents that are known to cause disease in healthy adults which is rarely serious and for which prevention or treatment options are available, or agents that pose a moderate risk to the environment.
RG 3Agents that are known to cause serious or fatal disease, particularly by the inhalation route, and for which there may be preventive or treatment options available, or agents that pose a high risk to the environment.
RG 4Agents that are likely to cause serious or fatal disease for which prevention or treatment options are not usually available, or those agents that pose a serious threat to the environment.

Biosafety Levels

The same regulatory groups have created Biosafety Levels (BSL) that define a set of laboratory practices, facilities and equipment that are appropriate to contain and safely work with the different Risk Groups. The determination of appropriate biosafety level for a project or for a laboratory is made by evaluating the agents in use and the specific procedures and experiments being performed with those agents. Unless specified by regulation, the determination of Biosafety Level for a project or laboratory is made by the 91原创 IBC in conjunction with the PI. In general, the Biosafety Level will be the same as the highest Risk Group for the agents involved. The following table gives an overview of Biosafety Levels; it is taken from the CDC BMBL 5th Edition, 2007. For a detailed description of Biosafety Levels, see the BMBL.

Table I - Summary of Recommended Biosafety Levels for Infectious Agents
BSLAgentsPracticesPrimary Barriers and Safety EquipmentFacilities (Secondary Barriers)
1Not known to consistently cause disease in healthy adults (RG1)Standard Microbiological PracticesNone requiredLaboratory bench and sink required
2
  • Agents associated with human disease
  • Routes of transmission include percutaneous injury, ingestion, mucous membrane exposure (RG2)

BSL-1 practice plus:

  • Limited access
  • Biohazard warning signs
  • 鈥淪harps鈥 precautions
  • Biosafety manual defining any needed waste decontamination or medical surveillance policies

Primary barriers:

  • Class I or II BSCs or other physical containment devices used for all manipulations of agents that cause splashes or aerosols of infectious materials PPE*:
  • Laboratory coats; gloves; face protection as needed

BSL-1 plus:

  • Autoclave available
3
  • Indigenous or exotic agents with potential for aerosol transmission
  • Disease may have serious or lethal consequences (RG3)

BSL-2 practice plus:

  • Controlled access
  • Decontamination of all waste
  • Decontamination of laboratory clothing before laundering
  • Baseline serum

Primary barriers:

  • Class I or II BSCs or other physical containment devices used for all open manipulation of agents PPE:
  • Protective laboratory clothing; gloves; respiratory protection as needed

BSL-2 plus:

  • Physical separation from access corridors
  • Self-closing, doubl door access
  • Exhaust air not recirculated
  • Negative airflow into laboratory
4
  • Dangerous/exotic agents which pose high risk of life threatening disease
  • Aerosol-transmitted laboratory infections have occurred; or related agents with unknown risk of transmission (RG4)

BSL-3 practices plus:

  • Clothing change before entering
  • Shower on exit
  • All material decontaminated on exit from facility

Primary barriers:

  • All procedures conducted in Class III BSCs or Class I or II BSCs in combination with full-body, air-supplied, positive pressure personnel suit

BSL-3 plus:

  • Separate building or isolated zone
  • Dedicated supply and exhaust, vacuum, and decontamination systems
  • Other requirements outlined in the text

* PPE 鈥 Personal Protective Equipment