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Principles & Concepts

The principles and definitions of the biological safety described in MS&T Biological Hygiene Plan. Biohazard classifications, biosafety containment levels (BSL1-4 & ABSL1-4), infectious agent Risk Groups (RG1-4), infectious dose, concentration, and immune status are defined in this section.

Key Risk Assessment Factors

  • Infectious Dose: The minimum number of microorganisms required to initiate an infection in a host. This threshold varies significantly—from a single organism to hundreds of thousands—depending on the specific agent, route of exposure, strain's virulence, and the host's immune status and susceptibility.
  • Agent Concentration & Volume: The quantity of infectious organisms per unit volume. Risk elevates as the concentration of viable agents or the total volume increases. Risk assessments must evaluate the culture media/reservoir, experimental procedures, and total fluid volume—noting that volumes exceeding 10 liters trigger specialized large-scale oversight.
  • Host Immune Status: The host's physiological capacity to recognize, resist, and overcome infectious agents. Susceptibility directly influences the risk of contracting a disease following exposure. Note: Standard CDC and NIH biosafety guidelines assume exposure to a population of immunocompetent individuals; heightened precautions may be required if working near immunocompromised populations.

Laboratory Biosafety Level Criteria

Biosafety levels (BSLs) prescribe specific combinations of laboratory practices, safety equipment, and facility design. These criteria are tailored to the operations performed, suspected routes of transmission, and overall laboratory function.

Biosafety Level 1 (BSL-1)

  • Scope: Work with well-characterized agents not known to consistently cause disease in healthy adult humans, presenting minimal hazard to personnel and the environment.

  • Containment & Facilities: Special containment equipment and dedicated facility features are generally not required.

  • Personnel & Supervision: Staff receive specific procedural training and operate under the supervision of a scientist with general microbiology or related expertise.

Biosafety Level 2 (BSL-2)

  • Scope: Work involving agents of moderate potential hazard to personnel and the environment.

  • Containment & Equipment: Procedures generating infectious aerosols or splashes must be conducted within Biosafety Cabinets (BSCs) or other physical containment. Extreme precautions are enforced for contaminated sharps.

  • Facility Access & Personnel: Access is restricted during active work. Personnel must hold specific training in handling pathogenic agents and work under competent scientific direction.

Biosafety Level 3 (BSL-3)

  • Scope: Research, diagnostic, or teaching facilities working with indigenous or exotic agents that pose a risk of serious or potentially lethal infection via aerosol transmission.

  • Containment & Equipment: All manipulations of infectious materials must occur within BSCs, physical containment devices, or by personnel equipped with specialized PPE.

  • Facility & Personnel: The facility features specialized engineering controls (e.g., directional airflow). Staff undergo specialized training in handling hazardous agents under the guidance of experienced scientists.

Biosafety Level 4 (BSL-4)

  • Scope: Work with dangerous and exotic agents posing a high individual risk of life-threatening, aerosol-transmitted laboratory infections.

Animal Biosafety Level Criteria (ABSL)

Animal Biosafety Levels establish containment practices, equipment, and facility standards for in vivo experiments with infected animals. In general, animal biosafety levels correspond to their in vitro BSL counterparts.

Animal Biosafety Level 1 (ABSL-1)

  • Scope: Work involving animals infected with well-characterized agents not known to cause disease in healthy adult humans, presenting minimal hazard to personnel and the environment.

Animal Biosafety Level 2 (ABSL-2)

  • Scope: Work involving animals infected with agents associated with human disease (hazards from ingestion, percutaneous exposure, or mucous membrane contact). Builds upon ABSL-1 standards.

  • Containment & Equipment: Procedures creating aerosols or splashes are conducted inside physical containment devices (e.g., BSCs).

  • Facility Access & Personnel: Facility access is restricted exclusively to essential personnel who are informed of potential hazards. Staff receive specific training in handling pathogens and infected animals.

Animal Biosafety Level 3 (ABSL-3)

  • Scope: Work with animals infected with indigenous or exotic agents presenting a risk of aerosol transmission and serious or lethal disease. Builds upon ABSL-2 standards.

  • Containment & Engineering: All manipulations of animals and infectious materials require physical containment or specialized PPE. Facilities require specialized engineering controls and negative-pressure HVAC systems.

  • Personnel: Personnel undergo advanced training in handling animals infected with high-consequence pathogens under expert scientific oversight.

Animal Biosafety Level 4 (ABSL-4)

  • Scope: Work involving dangerous or exotic agents posing high individual risks of life-threatening disease, aerosol transmission, or agents with unknown transmission risks.

Recombinant & Synthetic Nucleic Acid Guidelines (NIH Framework)

Per the NIH Guidelines, investigators must perform an initial risk assessment based on the Risk Group (RG) of the parent organism, categorized by human pathogenicity:

  • Risk Group 1 (RG1): Agents not associated with disease in healthy adult humans.

  • Risk Group 2 (RG2): Agents associated with human disease that is rarely serious, for which preventive or therapeutic interventions are typically available.

  • Risk Group 3 (RG3): Agents associated with serious or lethal human disease, for which preventive or therapeutic interventions may be available.

  • Risk Group 4 (RG4): Agents likely to cause serious or lethal human disease, for which preventive or therapeutic interventions are usually unavailable.

NIH Containment Designations

The NIH Guidelines define standard practices, containment equipment, and facility requirements across specialized research settings:

  • Standard Research Laboratories: Biosafety Levels 1 through 4 (BL1 to BL4)

  • Large-Scale Operations (>10 Liters): Large scale (BL-1 Large scale to BL-4 Large scale): large scale (over 10 liters) research and production governed by Good Large Scale Practices (GLSP)

  • Plant Research (Greenhouses): B -1P through BL-4P

  • Animal Research (Whole Animals): BL-1N through BL-4N

NIH Guidelines pdf version

NIH Guidelines