BSL-3

The Biosafety in Microbiological and Biomedical Laboratories (BMBL) is in principle the basis of design for every biocontainment facility in the U.S. and for many other parts of the world. Because of its far reaching effects on biocontainment, I am starting a new series on containment with a look at the latest version, the BMBL 5th Edition. My focus will be on understanding the document for BSL-3 and ABSL-3 containment design.

I will review some of the principles on which it is based, as well as some of the changes from the previous, 4th Edition that are relevant to BSL-3 design. In real-life application, the 5th Edition is relatively new; it was published in February 2007 and we are only now seeing its impact on completed projects. The emerging picture is that overall the BMBL 5th Edition represents continuity with previous editions. However, some new language and information in this edition present both challenges and opportunities that are worth identifying and discussing.

Before we examine some of the new language and features, I would like to begin with an important characteristic of the BMBL that is not new but continues to be misunderstood. The BMBL is not an overly prescriptive document, especially for BSL-3 requirements. Refer to the Summary of Recommended Biosafety Levels Tables at the end of Sections IV and V to see the basic requirements for BSL-3 and ABSL-3. They are intentionally very simple and do not include many features that you may think are required in a BSL-3 space: for example, room air exhaust HEPA filtration is not. But this is exactly right, as the basic requirements to handle the risk associated with working with dangerous pathogens under simple, low-risk procedures (such as simple diagnostic testing).

This approach is rooted in the concept that BSL-3 solutions are highly dependant on risk assessment; on the nature of specific pathogens and the nature of the work being conducted. There is no universal checklist for BSL-3 projects; no one-size fits all. Unlike in Lake Woebegone, we don’t want all children to be “above average.” We want each to be productive, safe, and affordable. To more clearly understand this approach, the 5th Edition provides an updated chapter on risk assessment which “represents the foundation—a code of practice for safe handling of infectious agents in microbiological and biomedical laboratories.”¹ It is important to use these tools and methods in conjunction with performance-based design criteria to determine the specific requirements for your particular program.

Appendix D: Agriculture Pathogen Biosafety
Continuing the examination of the necessary enhancements to basic BSL-3 space based on risk, the BMBL 5th Edition clarifies the effect agricultural concerns have on BSL facility design. The new Appendix D, Agriculture Pathogen Biosafety, provides guidance on what features are necessary when work is done with agents that are deemed Pathogens of Veterinary Significance.²

There are two principles to keep in mind that can help you apply Appendix D correctly. First, understand that the practices and control measures for BSL and ABSL in Sections IV and V of the BMBL have a different objective and emphasis than the practices and control measures found in Appendix D. They can be seen as two separate guidance documents developed by different groups: Sections IV and V by the CDC/NIH and Appendix D by the USDA. It may be self-evident, but the first guidance is designed to protect people: those working directly with or around the agent (the most at risk) and also those in the community. The agricultural guidance on the other hand is protecting animals or plants in the outside environment. Appendix D therefore emphasizes enhancements to the containment boundary to ensure that infectious material cannot escape the laboratory or animal room by air (as aerosols), with liquids, or on objects (including people) leaving the facility (as fomites). Barrier enhancements common to agricultural facilities include personnel showers on exit, movement (quarantine) restrictions on workers in contact with agricultural pathogens when outside the facility, greater air-tightness of rooms, and HEPA filtration of the exhaust and supply air. As an agricultural enhancement, the personnel shower is used to ensure that a person is not carrying a pathogen out on them. The shower is not designed to protect the person’s health. However, if the pathogen is infectious to humans as well as animals (a zoonotic agent), the risk assessment could require the same shower-out procedure for health-safety reasons also. As this example illustrates, the two guidance items co-exist but for separate reasons; and they are complimentary. You will never diminish health protection by adding additional environmental protection and vice-versa. Whether you will need to follow one or both sets of guidance requirements depends on the agent: whether you are working with human health risks or agricultural risks only, or risks to both populations.