BSL Basics

By Vince McLeod, CIH, Glenn R. Ketcham, CIH Article Posted: September 01, 2007

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Whether performing research or production, activities working with infectious micro-organisms, or laboratory animals, require the proper degree of protection – protection for laboratory personnel, the environment, and the local community. The protections afforded to these types of activities are defined as biosafety levels. Biological safety levels are ranked from one to four and are selected based on the agents or organisms on which the research or work is being conducted. Each level up builds on the previous level adding constraints and barriers. The Centers for Disease Control (CDC) and the National Institutes of Health (NIH) are our main sources for biological safety information for infectious agents. Their publication, Biosafety in Microbiological and Biomedical Laboratories,1 is a principle reference and the resource for much of the information presented in this month’s column. So, to get started we will summarize what the different biosafety levels encompass in terms of the typical biological agents used, safe work practices, specialized safety equipment (primary barriers), and facility design (secondary barriers).

The four biosafety levels were developed to protect against a world of select agents. These agents include bacteria, fungi, parasites, prions, rickettsial agents, and viruses, (probably the largest and most important group). In many instances the work or research involves vertebrate animals; everything from mice to cattle. When vertebrates are involved additional precautions and safety requirements are required. Using the most infectious agents also means extensive security measures are in place not only because of their virulence but also because of their potential for use in bioterrorism.

Biosafety Level 1
Biosafety Level one, the lowest level, applies to work with agents that usually pose a minimal potential threat to laboratory workers and the environment and do not consistently cause disease in healthy adults. Research with these agents is generally performed on standard open laboratory benches without use of special containment equipment. BSL-1 labs are not usually isolated from the general building. Training on the specific procedures is given to the lab personnel, who are supervised by a trained microbiologist or scientist.

BSL-1 Safety Tips
Standard microbiology practices are usually enough to protect laboratory workers and other employees in the building. These include mechanical pipetting only (no mouth pipetting allowed), safe sharps handling, avoidance of splashes or aerosols, and decontamination of all work surfaces when work is complete. Decontamination of spills is done immediately and all potentially infectious materials are decontaminated prior to disposal, generally by autoclaving. Standard microbiological practices also require attention to personal hygiene, i.e. hand washing and a prohibition on eating, drinking, or smoking in the lab. Normal laboratory personal protective equipment is generally worn consisting of eye protection, gloves, and lab coat or gown. Biohazard signs are posted and access to the lab is limited whenever infectious agents are present.

Biosafety Level 2
Biosafety Level 2 would cover work with agents associated with human disease, in other words pathogenic or infectious organisms posing a moderate hazard. Examples are the equine encephalitis viruses and HIV when performing routine diagnostic procedures or work with clinical specimens. Therefore, because of their potential to cause human disease, great care is used to prevent percutaneous injury (needle sticks, cuts and other breaches of the skin), ingestion and mucous membrane exposures, in addition to the standard microbiological practices of BSL-1.

BSL-2 Safety Tips
Contaminated sharps are handled with extreme caution, for example use of disposable syringe-needle units and appropriate puncture-resistant sharps containers, no direct handling of broken glassware, and decontamination prior to disposal. The laboratory’s written biosafety manual details any needed immunizations (e.g. Hepatitis B vaccine or TB skin testing) and whether serum banking is required for at-risk lab personnel. Access to the lab is more controlled than for BSL-1 facilities. Immuno-compromised, immuno-suppressed, and other persons with increased risk for infection may be denied admittance at the discretion of the laboratory director.

BSL-2 labs must also provide the next level of barriers, i.e. specialty safety equipment and facilities. Preferably, this is a Class II biosafety cabinet or equivalent containment device for work with agents and an autoclave or other suitable method for decontamination within the lab. A readily available eyewash station is needed. And self-closing lockable doors and biohazard warning signs are also required at all access points.

Biosafety Level 3
Yellow fever, St. Louis encephalitis, and West Nile virus are examples of agents requiring BSL-3 practices and containment. These are indigenous or exotic agents that may cause serious or lethal disease via aerosol transmission, i.e. simple inhalation of particles or droplets. The pathogenicity and communicability of these agents dictates the next level of protective procedures and barriers.

BSL-3 Safety Tips
Add to all the BSL-2 practices and equipment even more stringent access control and decontamination of all wastes, including lab clothing, before laundering all within the lab facility. Baseline serum samples are collected from all lab and other at-risk personnel as appropriate.

More protective primary barriers are used in BSL-3 laboratories including solid-front wrap around gowns, scrub suits or coveralls such as Tyvek®, and respirators as necessary. Facility design should incorporate self-closing, double-door access separated from general building corridors. The ventilation must provide ducted, directional airflow by drawing air into the lab from clean areas and with no recirculation.

BSL-4,Health and Safety,BSL-3

BSL Basics