III. WORKING SAFELY WITH BIOLOGICAL MATERIALS

A. Exposure Control

The term "containment" is used in describing safe methods for managing infectious agents in the laboratory environment where they are being handled or maintained. The purpose of containment is to reduce or eliminate exposure of laboratory workers, other people, and the outside environment to potentially hazardous agents.
The three elements of containment include laboratory practice and technique, safety equipment, and facility design.

Laboratory Practice and Technique

The most important element of containment is strict adherence to standard microbiological practices and techniques. Persons working with infectious agents or infected materials must be aware of potential hazards, and must be trained and proficient in the practices and techniques required for handling such material safely. The PI or laboratory supervisor is responsible for providing or arranging for appropriate training of personnel.

Each PI should identify specific hazards that will or may be encountered, and consider practices and procedures needed to minimize or eliminate risks. Personnel should be advised of special hazards and are expected to follow the required practices and procedures.

Safety Equipment (Primary Barriers)

Safety equipment includes biological safety cabinets, enclosed containers, and other engineering controls designed to eliminate or minimize exposures to hazardous biological materials. The biological safety cabinet (BSC) is the principal device used to provide containment of infectious splashes or aerosols generated by many microbiological procedures. More information on BSCs may be found in Section IV.B.

Safety equipment may also include items for personal protection such as personal protective clothing, respirators, face shields, safety glasses or goggles. In some situations, personal protective clothing may form the primary barrier between personnel and the infectious materials.

Facility Design (Secondary Barriers)

The design of a facility is important in providing a barrier to protect those working inside and outside the laboratory and to protect people or animals in the community from infectious agents which may be accidentally released from the laboratory. Facilities must be commensurate with the laboratory's function and the recommended biosafety level for the agent being manipulated.

The secondary barrier(s) needed will depend on the risk of transmission of specific agents. For example, all Princeton University research falls within Biosafety Levels 1 and 2 (see Biosafety Levels below) and exposure risks involve direct contact with the agents, or inadvertent contact through contaminated work environments. Secondary barriers in these laboratories includes separation of the laboratory work area from public access, availability of a decontamination facility (e.g., autoclave) and handwashing facilities.

B. Laboratory Biosafety Levels (top)

CDC-NIH has established four levels of biosafety, based on the degree of hazard associated with an organism, to describe the combination of laboratory practices and techniques, safety equipment, and facilities needed to protect against exposure. These four biosafety levels (BSL) require successively more restrictive practices and facilities as work moves from the least restrictive BSL1 to work with the highest hazard level of BSL4. Exposure to biohazardous agents is intended to be prevented or limited by establishing and following the appropriate biosafety level practices and conditions. Research in Princeton University facilities is currently limited to BSL1 and BSL2. (See Section IV.A. for an outline of good practices at BSL1 and BSL2).

BSL1 applies to the basic level of containment and essentially represents good microbiological practice with no special primary or secondary barriers required. This applies to work with defined and characterized strains of viable microorganisms not known to consistently cause disease in healthy adult humans. This includes such organisms as the bacteria Bacillus subtilis, Vibrio harveyi, or host/vector strains of E coli and yeast Saccharomyces cerevisiae.

BSL2 applies to work with a broad spectrum of moderate-risk agents that are generally present in the environment at large and are associated with human disease of varying severity.

All of the viral agents used in campus research, such as adenovirus, cytomegalovirus, and other herpes viruses fall within the BSL2 level of work. Other microorganisms assigned to this containment level include salmonella spp., toxoplasma spp., hepatitis B, and HIV. With the use of good microbiological techniques, much of this work can be done on open bench tops as long as there is limited potential for splashes and aerosol creation. In addition to BSL1 conditions, this level of work also requires that:

• Laboratory personnel have specific training in handling any pathogenic agents used
  
• Access to the laboratory is limited when BSL2 work is being done
  
• Gloves and other suitable personal protective equipment are worn
  
• Extreme precautions are taken with contaminated sharps
  
• Biosafety cabinets are used when there is potential for splash or aerosol creation

BSL3 and BSL4 apply to work with exotic agents of increasingly greater potential for causing serious human illness or death. No work at the BSL3 or 4 is currently being done and facilities that would meet the requirements of these biosafety levels are not available at Princeton.

A good summary of requirements at each laboratory biosafety level can be found at http://bmbl.od.nih.gov/sect3tab1.htm.

C. Animal Biosafety Levels (top)

A similar set of four biosafety levels are provided for work with vertebrate animals infected with agents which may infect humans. These Animal Biosafety Levels, ABSL 1 thru 4, provide for practices, equipment, and facilities that are comparable to the laboratory biosafety levels described above. However, there are unique hazards associated with infected animals that must be understood by those personnel with animal contact and addressed in the animal facility. Animal activity can create aerosols and bites and scratches can occur.

See http://bmbl.od.nih.gov/sect4tab1.htm for a good summary of the Animal Biosafety Levels.

Last Page

Next Page