A biohazard can broadly be defined as any biological material that poses a risk to human health or the environment. In a laboratory setting, the term encompasses agents with a biosafety level (BSL) of 2 or above and includes such entities as bacteria, viruses, parasites and certain types of fungi—as well as any material that may harbor them. To avoid exposure to biohazards, researchers should always handle potentially harmful material with care. This means performing a comprehensive risk assessment before commencing any lab work, understanding the biosafety level of sample material, using suitable personal protective equipment (PPE), implementing effective cleaning and decontamination strategies, and ensuring biological safety cabinets (BSCs) and CO2 incubators are fit for purpose.
Start with a risk assessment
Before undertaking any type of lab work, it is essential that researchers perform a comprehensive risk assessment. This includes developing, implementing, and documenting a detailed biosafety plan that is commensurate with the biological material being handled and its intended use. As well as describing the biohazardous characteristics of the material in question (e.g. pathogenicity, effective dose, host range, transmission method), an effective biosafety plan should also identify any procedural hazards (e.g. spills and splashes, inhalation, sharps injuries) and the associated biosafety risk. Critical factors to consider during risk assessment include the biosafety level of the material in question; the integrity of any safeguards designed to protect personnel and the environment from exposure to potentially harmful agents; and whether those who will carry out the work have received appropriate training. Once complete, the risk assessment should be assessed and approved by qualified biosafety professionals. Moreover, following any change that could impact risk, or any “near-miss” or real-life incident, the risk assessment should be reviewed to confirm it remains fit-for-purpose.
Understand the biosafety level of your samples
To ensure researchers handle biohazardous material appropriately, a set of standards has been established that assigns work involving potentially harmful agents a biosafety level of 1 through 4. BSL-1 is the lowest level and encompasses the handling of agents that present little or no risk to laboratory personnel or the environment. Examples include canine adenovirus (the cause of infectious hepatitis in dogs) and Saccharomyces cerevisiae (commonly referred to as baker’s yeast). Material classified as BSL-1 can be manipulated on an open bench provided safe working practices are followed—spills should be cleaned up immediately, work surfaces should be decontaminated after use, waste should be disposed of correctly, and basic PPE (eye protection, gloves, and a lab coat) should be worn.
BSL-2 is the next level up and covers the handling of agents associated with human disease. These include bacteria such as Mycoplasma pneumoniae (the cause of respiratory illnesses ranging in severity from mild chest colds to pneumonia) and viruses such as Herpes simplex (associated with cold sores). Work involving BSL-2 agents should be performed in a class I or class II biological safety cabinet to protect against aerosols, and contaminated waste should be autoclaved before it leaves the facility. Again, suitable PPE should be employed—in certain situations, it may be deemed necessary to double glove—and it is recommended that access to the laboratory be restricted.
BSL-3 agents can cause serious, or even lethal, disease and pose a significant threat to the environment. Examples include Yersinia pestis (the bacterium that causes plague) and West Nile virus (a mosquito-borne flavivirus that can cause a fatal neurological condition in man). Any manipulation of material classified as BSL-3 should take place in a class II or class III biological safety cabinet and should be carried out by personnel wearing specialized protective clothing that must be either disposable, or be decontaminated before laundering. Other critical features of a BSL-3 lab are sealed walls, ceilings, and windows; self-closing double-doors that separate the lab from shared corridors; a non-recirculating airflow; and strictly limited access.
BSL-4, the highest biosafety level, encompasses the handling of material designated as being extremely dangerous and posing an acute risk of life-threatening disease. Examples are the hemorrhagic fever viruses Ebola, Lassa, and Marburg, all of which are characterized by fever and bleeding disorders and have high associated mortality rates. BSL-4 work is typically performed in a class III biological safety cabinet (better known as a glove box)—although you can also use a Class II BSC with a full body suit—and requires that numerous other safety precautions be put in place.
To determine the BSL of the biological material in question, researchers may choose to consult the American Biological Safety Association (ABSA) website. This provides an easy-to-use search function that enables users to mine an extensive, regularly-updated risk group database encompassing bacterial, viral, fungal, and parasitic organisms. The Biosafety in Microbiological and Biomedical Laboratories (BMBL) is another useful resource; this key advisory document recommends best practices for the safe conduct of work in biomedical and clinical laboratories from a biosafety perspective and is based on protocol-driven risk assessment. However, it is important to remember that while BSL levels can help guide users, biosafety hinges on the initial risk assessment.
Select a suitable biological safety cabinet
Biological safety cabinets provide an essential first line of defense for those working with biohazardous material and should be chosen to align with the biosafety level of the samples being handled. They range from class I through class III, with class III BSCs offering the highest level of protection. BSL-2 material is typically manipulated in either a class I or class II BSC, more commonly the latter; this is because class II BSCs protect the product as well as personnel and the environment by HEPA filtering air both before it enters the enclosure and before it is expelled. In contrast, class I BSCs provide zero product protection since air is only HEPA filtered prior to expulsion. Material classified as BSL-3 is usually handled in a class II BSC, although in some instances a class III BSC may be considered more appropriate. As previously mentioned, material classified as BSL-4 is typically handled in a class III BSC, although BSL-4 material may also be manipulated in a class II BSC where personnel are protected by a bubble suit. Again, the risk assessment is fundamental in determining appropriate working practices and selecting suitable engineering controls.
For BSCs to function effectively, it is important that they are used properly. This means decontaminating the enclosure prior to use and loading it with everything necessary to perform the experiment in question before initiating any work. Another way of minimizing biohazard-associated risk is to position items such that they leave ample room for maneuver and encourage working from clean to dirty; this not only helps reduce the chance of spills or cross-contamination, but also helps prevent disruption to the airflow by streamlining sequential movements.
Don’t overlook the importance of CO2 incubators
Although biological safety cabinets are often considered to be one of the highest risk areas in any lab handling biohazardous material, it is vital to remember that CO2 incubators represent another potential source of contamination. Because CO2 incubators are routinely used for culturing virally infected human cells, incubating patient serum samples, and propagating various cultures, it is essential to keep them in good working order.
To ensure the safety of personnel, CO2 incubators should, first and foremost, be easy to clean. Models fitted with a seam-free stainless steel inner chamber are widely available and many include an auto-sterilization option (e.g. using hot air) for an extra level of protection. Fanless operation is another feature that can lessen the risk of contamination; fan-free systems also provide the added benefit of reducing background noise in the lab. Lastly, where CO2 incubators can be stacked, this frees up valuable space and minimizes the likelihood of collisions that could result in biohazardous material being spilt.