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Biosafety Risk Assessment / Risk Groups 

The biological risk assessment process is used to identify the hazardous characteristics of an infectious or potentially infectious agent or material, if known; the activities that can result in a person's exposure to an agent; the likelyhood that such exposure will cause a laboratory associated infection (LAI); and the probable consequences of such an infection.  The information identified by risk assessment will provide a guide for the selection of the appropriate mitigations, including the application of Biosafety Levels and good microbiological practices, safety equipment, and facility safeguards that can prevent LAIs. Risk Assessments should be performed prior to beginning work with a biohazardous agent or at any time when a change occurs to existing procedures, protocols and SOP's. A six-step approach to risk assessment is summarized below.

  1. Identify hazardous characteristics of the agent and perform an assessment of the inherent risk (i.e. what is the agent Risk Group?) Risk Group classifications indicate the specific hazards associated with a particular bacteria, virus, or other biohazard. Risk Group classifications are based on an agent's capability to infect and cause disease in a susceptible host, severity of disease, and the availability of preventative measures and effective treatments.  Other items of concern include possible routes of transmission of infection, infectious dose, host range, genetic characteristics of the agent. Consult the references listed below for your agent(s).
  2. Identify laboratory procedure hazards. Procedures that produce aerosols, working with sharps, working with animals (zoonotic diseases), working with large/concentrated volumes of biohazardous agent(s), working with cell cultures derived from human/primate cultures or materials (bloodborne diseases) as well as many other procedures carried out in a typical laboratory can have varying levels of risk associated with them.
  3. Determine the appropriate BSL and select additional precautions indicated by the risk assessment  The selection of the appropriate BSL and any additional laboratory precautions require a comprehensive understanding of the practices, safety equipment, and facility safeguards described in the BMBL 6th ed.
  4. Review the selected safeguards with a biosafety professional, subject matter expert, and the IBC or equivalent resource This review is strongly recommended and may be required by regulatory or funding agencies.
  5. Evaluate the proficiencies of the staff regarding safe practices and the integrity of safety equipment Laboratory directors or principal investigators should ensure that laboratory personnel have acquired the technical proficiency in the use of microbiological practices and safety equipment required for safe handling of the agent(s). This includes the ability to recognize hazards and how to handle emergency situations and obtain assistance if necessary.
  6. Regularly revisit and verify risk management strategies and determine if changes are necessary This includes a regular update of biosafety manuals and SOPs when changes in procedures or equipment occur.

Click for more on Biological Risk Assessment (Section II - BMBL 6th ed.)

Learn more about Hazard Reviews and Safety Protocols

Risk Groups

Infectious agents or pathogens are disease-causing microorganisms.  There are hundreds of microorganisms that cause disease in humans and animals. They can be classified as bacteria, fungi, viruses, prions, or parasites. The principal hazardous characteristics of an agent are its capability to infect and cause disease in a susceptible human, animal or plant host, its virulence as measured by the severity of disease, and the availability of preventive measures and effective treatments for the disease. Other hazardous characteristics of an agent include probable routes of transmission of laboratory infection, infective dose, stability in the environment, host range and endemic nature.  Each infectious agent or microorganism can be categorized by four levels of hazard known as Risk Groups. It is important to keep in mind that in many instances a risk group will correlate with a biosafety level (e.g. RG-2 agent will be handled at BSL-2) but they are not equivalent (e.g. some RG-3 agents may be safely manipulated at a BSL-2 under certain conditions).

NIH Guidelines Definition of Risk Groups

Risk Group 1 (RG1) - Agents that are not associated with disease in healthy adult humans.  This group includes a list of animal viral etiologic agents in common use.  The agents represent no or little risk to an individual and minimum risk to the community.

Risk Group 2 (RG2) - Agents that associated with human disease which is rarely serious and for which preventative or therapeutic interventions are often available.  These agents represent moderate risk to an individual but a low risk to the community.

Risk Group 3 (RG3) - Agents that are associated with serious or lethal human disease for which preventative or therapeutic interventions may be available.  These agents represent a high risk to the individual and a low to moderate risk to the community depending on the pathogen.

Risk Group 4 (RG4) - Agents ("Exotic Agents") that are likely to cause serious or lethal human disease for which preventative or therapeutic interventions are not ususally available.  The agents represent a high risk to the individual and a high risk to the community.

Routes of Exposure and Disease Transmission

For biological agents to cause disease, they must first enter of invade the body in sufficient numbers. Routes of entry include oral, respiratory, parenteral, mucus membrane, and animal contacts (bites or scratches). Once inside the body, biohazardous agents must colonize cells, tissues and/or organs and overcome the body's defense mechanisms in order to cause disease.

Other factors contribute to an individual's susceptibility to the disease process. These include age, immunological state, predisposing conditions, occupation physical and geographic location.  

Investigations of Laboratory Acquired Infections (LAIs) have identified 5 principal routes of laboratory transmission. These are parenteral inoculations with syringe needles or other contaminated sharps, spills and splashes onto skin and mucus membranes, ingestion, animal bites & scratches, and inhalation exposures to infectious aerosols. The first four routes of transmission re fairly easy to detect. However, up to 80% of all reported LAIs are suspected to be caused by infectious aerosols thereby making them the predominant route for transmission of biologically hazardous agents.

Route of Exposure

Protective Measures

Mucous Membranes – Exposure via the mucous membranes, eyes, nose, or mouth due to splash/splatter.

Protect face by:

•    Wearing safety glasses and a surgical mask or a full face shield.

•    Working in a BSC or behind a protective shield.

•    Following good microbiological practices.


Inhalation – Breathing in respirable aerosols (particles <5 µm) due to centrifuge leaks, spills, or aerosol-generating procedures such as pipetting and homogenizing

Avoid exposure to aerosols by:

•    Working in a BSC.

•    Using sealed rotors or canisters when centrifuging.

•    Following good microbiological practices.

•    Using respiratory protective equipment.


Ingestion – Exposure from mouth pipetting or eating, drinking, or smoking in the laboratory.

Prevent exposure via ingestion by:

•    Never eating, drinking, or smoking in the laboratory.

•    Always using mechanical pipettors.

•    Following good microbiological practices.

•    Using gloves and frequent hand washing.


Percutaneous – Exposure through intact or non-intact skin via needlestick, puncture with a contaminated sharp object, animal scratch or bite, or through wounds, abrasions, or eczema.

Prevent percutaneous injuries by:

•    Substituting plastic for glass.

•    Using extreme caution and/or engineering controls with sharps. i.e., never recapping needles.

•    Discarding sharps immediately into a rigid leakproof sharps container.

•    Wearing cut-resistant gloves and sleeves.

•    Properly restraining animals.

•    Covering non-intact skin with waterproof bandages and wearing double gloves.


Indirect Contact – Touching mucous membranes or non-intact skin with hands that have been in contact with contaminated surfaces, such as benches, phones, and computers, or hands that were not washed after working.

Prevent indirect exposure by:

•    Decontaminating work surfaces frequently (at least once a day)

•    Always washing hands when finished working, after removing gloves, and before leaving the lab.

•    Not touching face (either with gloves or non-gloved hands - good personal hygiene).

•    Not applying cosmetics within the laboratory.

References - Biological Agent Risk Groups