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The safe laboratory – protection through technology

When biomedical researchers or diagnosticians work with potentially contagious materials like cell cultures, blood or tissue, they need absolute protection from pathogens. Both safety measures in the workspace and the correct tools and materials are key here. Learn in our Topic of the Month what is important for protection in the lab and what a safe laboratory looks like.

1 - Laboratory safety: infection prevention in the work area

What goes in, must not come out - and must also not cause harm to anyone working inside the lab. That's perhaps a nice way of summing up "laboratory safety" in one sentence - at least wherever pathogens are handled in biological and medical settings. The necessary laboratory safety precautions primarily depend on what is waiting "inside".

Many pathogens have caused a major uproar in recent years. In the past, the Zika virus, EHEC, SARS, MERS and right now SARS-CoV-2 Coronavirus have emerged as new pathogens that infect humans and have been recognized as having animal origin. Others, including Ebola, measles, various influenza (flu) viruses or Marburg virus, have been around for a long time and continue to cause occasional disease outbreaks in some regions. These viruses not only occur in nature, in humans or animals but are also stored at research laboratories around the world in an effort to find potential medicines and vaccines as solutions.

Safety/Risk groups for biological agents

Biological agents at work such as pathogens are classified into four Risk Groups following international rules and regulations. The European Union covers this in its Directive 2000/54/EC, which is implemented by the member states in national standards for occupational safety and health. The United States follows the laboratory safety regulations as outlined by the Centers for Disease Control and Prevention (CDC).

Risk Groups are classifications that describe the relative hazard posed by infectious biological agents or toxins in the laboratory as it refers to the likelihood of causing disease in humans and transmission to the population and reflect potential treatment and prevention options. To put it in a nutshell, the more infectious and difficult it is to treat the agents, the safer the laboratory and working conditions must be.

Biological laboratories are classified into four corresponding Safety Levels, which are referred to as biological safety or biosafety levels (BSL). Risk Group 4 pertains to the most serious and deadly pathogens in the world and includes viruses such as the smallpox variola virus or the Ebola and Marburg virus, which cause hemorrhagic fever, a severe and often fatal illness in humans. These pathogens can be readily transmitted from one individual to another, rendering an effective treatment impossible. The 2014 outbreak of Ebola virus disease caused more than 11,000 deaths but has shown that intensive medical treatment can be effective until the body has successfully fought the infection. Since 2015, there has been a potential Ebola vaccine. These types of viral agents can only be handled in BSL- 4 laboratories, ensuring the highest level of biocontainment.

Risk Group 3 pathogens are also infectious agents that cause serious diseases in humans. However, treatments or prevention for these diseases are typically an option. Agents include influenza, human immunodeficiency and hepatitis viruses. SARS-CoV-2 virus also falls into the Risk Group 3 category for now.

Pathogens of Risk Group 2 pose a moderate risk and transmission is rather unlikely. There are effective treatments and preventive measures in place. Finally, Risk Group 1 contains non-pathogenic organisms unlikely to cause human or animal disease.

Safety thanks to technology

Prevention is key when it comes to laboratory work. Laboratory-acquired infection of staff or the release of infectious biological materials must be avoided at all costs. The outbreak of the Marburg virus in 1967 in the Hessian town of Marburg, Germany, shows the serious consequences of insufficient laboratory safety conditions. Laboratory workers of a pharmaceutical company became infected after handling tissue of test monkeys, leading to the initial recognition of the disease. Seven deaths were reported, while 30 people were infected. Since then, there have been recurring outbreaks of Marburg virus in various African countries until 2014.

Apart from stringent education and instruction in occupational health and safety, various laboratory safety measures and personal protective equipment of each laboratory worker prevent humans from coming into direct physical contact with potentially infectious agents. Find out how these methods work and how they ensure lab safety in our Topic of the Month.

2 - BSL-4 laboratories: highest levels of safety and protection

Laboratories are sectioned into four biosafety levels to dictate the precautions required to isolate dangerous biological agents. The highest level of biological safety, BSL-4, is perhaps the most well-known when we think of containing pathogens and microbes. However, the fewest number of laboratories actually fall into the BSL-4 category because they must meet the strictest, most complex and subsequently most expensive requirements.

The (official) number of biosafety level 4 (BSL-4) facilities around the world is limited. Nevertheless, they are very popular in movie or television settings, usually featuring scientists in full-body pressurized protective suits who work with highly infectious deadly pathogens that, despite all caution, manage to escape and become the main cause of disaster or the scientists frantically try to find a way to prevent a catastrophic outbreak.

To prevent infectious biological materials from escaping in real life, BSL-4 laboratories are subject to countless safety and security measures. It all starts with the right protective lab equipment and clothing. Before scientists enter the lab, clothing is put on in successive sealed airlock chambers. Street or personal clothes must not be worn inside the laboratory. The employees must take them off and – after a decontamination shower in the airlock - put on special undergarments before dressing in pressurized protective suits. Wearing these full-body protective suits for any length of time can be physically exhausting as they restrict movement and – depending on the material – can be very heavy. That’s because they not only have to successfully protect the wearer, but must also stand up to chemicals, disinfection, abrasion, wear and tear.

The suits protect against direct contact with sample material and, as a result, eliminate the risk of smear infection. They are also supplied with fresh, filtered oxygen from the outside and are under constant positive pressure. In case of damage to the suit, this ensures that no laboratory air that contains highly transmissible airborne pathogens can enter. The gear also includes two pairs of gloves. The outer pair is tightly attached to the suit.

While the air pressure in the safety suits is positive to prevent pathogens from getting inside and keeping them away from the user, the lab is kept under negative pressure (lower than the other lab premises). The laboratory’s walls, ceilings, floors and airlock security doors are airtight. As long as negative pressure is maintained, this measure prevents pathogens from escaping the lab and being released into the atmosphere in case of minor damages to the outer layer or seals. This hermetically sealed setting also facilitates safe disinfection with gases.

From an architectural perspective, the laboratory is never directly connected to the exterior wall of the building. There is always another corridor or other space in between that separates the laboratory from the outside world.

To leave the lab, laboratory staff in their protective suits pass through the airlock chambers again, though there is an additional step they must take: A chemical shower disinfects the suits for several minutes, followed by hot water and soap. This includes a disinfectant dunk bath for the soles of the overshoes or boots and ensures that there are no more biological agents left on the suits before leaving the laboratory. Materials such as sample containers are also sterilized if they are brought into the laboratory.

Needless to say, any item that is no longer needed cannot simply be thrown away. Any work equipment must be safely discarded. This is done by thermal sterilization treatment in pass-through autoclave systems. Material that must be disposed is placed in the autoclave inside the laboratory. The system sterilizes all objects using a combination of pressure, heat and water vapor (steam). Many medical and laboratory devices are not damaged during this procedure and can be reused. This process inactivates biological samples to where they are then unable to cause an infection.

But there is more that happens behind the walls of the laboratory: Breathing air, water, and liquid waste must also be filtered or sterilized, respectively. HEPA (high-efficiency particulate air) filters are used to clean the air. They are composed of a mat of randomly arranged fibers. These fibers are typically comprised of fiberglass that can trap airborne particles. Liquid waste like water is also subject to chemical or thermal sterilization.

In the real world, work in a BSL-4 lab is evidently not nearly as glamorous and heroic and much less prone to error than television would have us believe. In fact, it is shaped by countless tight security measures that must be taken to safely handle dangerous pathogens, such as Ebola or Marburg virus.

3 - Laboratory work: the right personal protective equipment is crucial

When working with infectious materials and organisms in the laboratory, safe handling and appropriate training are of utmost importance. Another central component is personal protective equipment designed to prevent contact with tissue, liquids and aerosols and protect the wearer.

Depending on the biological safety level set for the laboratory facility, employees might be allowed to wear their own street clothes (for biosafety levels BSL-1 and BSL-2), but they must also put on a laboratory coat on top of this layer. Biosafety level 3 laboratories (BSL-3) require a tie-back or solid-front wraparound gown, scrub suits or coveralls and closed-toe shoes. It is important for personal protective equipment to be customized. This means it must only be worn by the designated employee the gear was fitted for.

The use of personal protective equipment is always subject to the materials and the hazard they present. Not all biological agents require full-body protection. At any rate, lab coats and coveralls must prevent the wearer’s clothing from biocontamination. There must also be a separate changing room. Work clothes are collected here and distributed for laundering or disposal.

To guard from chemical splashes, associates should also wear eye protection. Options include safety goggles and face shields. Face masks are used to cover the mouth and nose area. However, these masks do not offer respiratory protection against aerosols containing pathogens. This requires special system filters. They must be able to filter out infectious particles or droplets that are smaller than 5 µm (microns) as some of them can spread across the work station.

Clean air thanks to particle filters

The simplest and best solution in this case are so-called FFP3 masks (FFP stands for filtering face piece), which have to fit as closely as possible over the wearer’s mouth and nose. Filter materials behind the exhalation valve vary and include activated carbon, which filter many particles from the air. The major drawback of these masks is that they must be tight-fitting. The fit largely depends on the wearer’s physiognomy, but beards can be a problem in this case. What’s more, breathing is difficult if the mask is worn for long periods of time.

Another alternative are wearable filter systems, which can be combined with helmets or hoods and a tight, secure-fit visor. They use HEPA (high efficiency particulate air) filters to purify the air by using fiberglass fibers to trap and capture particles that are smaller than 1 µm. These systems make breathing easier and provide a better and more secure fit than FFP3 masks. Generally, however, this equipment cannot be worn indefinitely because it is physically demanding and the filter materials don’t last forever and have to be changed.

To prevent biological agents from escaping the lab or avoiding exposure, labs typically use so-called biosafety cabinets or microbiological safety cabinets. This is an enclosed, ventilated laboratory workspace that can be adjusted by positioning the safety glass sash. The employee works in the space that’s created under the opened window sash. To prevent the escape of aerosols, the air is extracted from inside the cabinet and passed through a particulate air filter. Laminar airflow provides an extra layer of protection. Air is blown from the top of the hood straight down and suctioned. This airflow serves as an additional barrier against particles from inside the biosafety cabinet. It is very precisely adjusted and can be easily disturbed by devices inside the cabinet or external turbulence in the lab such as the air conditioning system.

An even safer option is a totally enclosed, ventilated cabinet with leak-tight construction and attached rubber gloves for performing operations in the cabinet. Materials have to be brought in and removed through an airlock. Both types of biosafety cabinets are maintained under negative pressure and supply air is drawn in through HEPA filters. This ensures that aerosol generated within the cabinet is contained within the cabinet even in case of damage.

Personal protective equipment – Building block of a safe workplace

These measures protect workers in the laboratory. They vary depending on the specific substances used and the potential hazard they pose. Added to this are organizational precautions including lab-specific training of employees, access controls, cleaning and disinfection measures, as well as structural provisions, such as the safe operation and allocation of spaces within the laboratory as designated storage spaces or changing rooms. This also includes the spatial separation of the laboratory work area and – for biosafety levels BSL-3 and BSL-4 - safe building services that filter and sterilize exhaust air and waste water and guarantee the safe disposal of waste and incidentals.

Personal protective equipment and work practices are just two building blocks of the overall laboratory safety principles and concepts that – combined with the application of many other safety precautions - address the safe handling and containment of infectious microorganisms and hazardous biological materials.

The right protective equipment is key when working with infectious materials.

Details

  • Germany
  • Timo Roth