Biohazards are harmful organisms or byproducts, including bacteria, viruses, medical waste, and toxins. Precautions are necessary when working with them, including using protective equipment and following strict protocols. The CDC has four levels of biohazard, with increasing precautions for more dangerous pathogens.
A biohazard, also known as a biohazard, is an organism or byproduct of an organism that is harmful or potentially harmful to other living things, primarily humans. Common types of biohazards include bacteria, viruses, medical waste, and toxins produced by organisms. The ‘biohazard’ symbol is a familiar sight in hospitals and any item carrying it should be treated with extreme caution. Biohazards vary in their degree of severity and the precautions employed during handling, storage or disposal are determined accordingly.
Chemical and biological hazards differ in that the latter can potentially pass from person to person. This makes it especially important that all precautions are strictly observed by those who work with or come into contact with biologically hazardous materials. In the worst case, inadequate precautions or failure to observe them could lead to a major outbreak of a deadly disease. This is extremely unlikely, however, as establishments that research infectious disease-causing agents are carefully designed to prevent accidental release and have strict biosafety rules.
Working with biohazards
Hospital staff routinely come into contact with potentially hazardous materials, such as used syringes and discarded dressings. These are normally placed in specially marked bags and containers clearly marked for incineration. The use of disposable gloves, combined with basic hygiene practices, such as frequent hand washing and disinfecting surfaces, helps prevent these materials from causing illness.
The need to develop new treatments and vaccines means there is sometimes a need for people to work with life-threatening biological agents. Bacteria can acquire resistance to antibiotics, so new compounds or alternative treatment methods need to be found. Some viruses mutate rapidly, making vaccines ineffective and requiring new ones to be developed and tested. In other cases, there has never been a vaccine. Research into dangerous microorganisms, or pathogens, is carried out at highly specialized facilities, which employ a variety of precautions, procedures and equipment to prevent infection and escape.
Equipment and precautions
Microorganisms could potentially escape from laboratories either through infection of personnel or directly, through materials originating from the laboratory without being decontaminated. This could include waste material, clothing worn by staff, or aerosols – tiny droplets or suspended particles – that could leave the building through doors, windows or ventilation systems. When handling biohazards, a number of devices are used.
A biological safety cabinet (BSC) is employed when working with pathogens where there is a risk of splashing or aerosol formation. It is a self-contained unit with its own air supply into which the sample is placed. Laboratory personnel work with the material using protective gloves integrated into the cabinet.
High Efficiency Particulate Air Filters (HEPA) can also be employed to filter all air leaving the work area. Another common precaution is to have negative air pressure within the hazard area so that when the doors are opened the air will flow in rather than out. In extreme cases, personnel may need to wear protective suits sealed with their own air supply.
Precautions include taking extra care with sharp tools, limiting access to areas handling dangerous pathogens to suitably qualified individuals, and ensuring that nothing leaves the laboratory without first being decontaminated. This can include people who may need to shower before leaving. Generally, personnel will be required to put on appropriate laboratory attire before entering the hazardous area and change back on when exiting. In addition to standard procedures, there are additional requirements relating to the nature of the hazardous material.
Biohazard levels
In the United States, the Centers for Disease Control and Prevention (CDC) has determined four levels of biohazard. A similar system exists in Europe and many other parts of the world. The categories depend on factors such as the infectivity of the agent, the severity of the disease it can cause, and whether or not there are effective treatments and vaccines. If any of these factors are unknown, they will typically be assigned the highest level of risk until more information becomes available.
Biohazard level 1 (BSL-1) is assigned to agents that generally do not cause disease in healthy humans. An example would be bacillus subtilis, a common soil bacterium that is highly studied by geneticists and can occasionally cause disease in people with severely weakened immune systems. No special containment is required for these agents and normal microbiology laboratory procedures, such as wearing gloves and a face mask, are adequate. Agents are considered suitable to work with university students and staff in training.
BSL-2 is for agents that can cause disease, even serious, in healthy humans, but which already exist in the external population and are not transmissible by inhalation. These agents can cause infection only through direct contact with infected material through cuts and abrasions or through ingestion. Examples are human immunodeficiency virus (HIV), hepatitis B virus and salmonella. Biohazard symbols must be clearly displayed and BSCs or similar devices are used for any work that could cause splashes or produce aerosols. An autoclave must be present to allow the sterilization of the instruments. Access to BSL-2 areas is restricted to trained personnel.
BSL-3 applies to pathogens that cause serious, life-threatening disease that can spread through the air, such as the bacterium that causes tuberculosis. These microorganisms can infect without direct contact with contaminated material, so they require particularly stringent precautions. Access to the work area is very limited and BSCs are used for all work with materials that may contain the pathogen.
BSL-4 is reserved for pathogens that cause diseases with high mortality rates and for which there are no effective treatments or vaccines, such as Marburg virus. It can also be used for agents whose characteristics are unknown or not fully understood, such as a new strain of influenza or a disease that has not previously been seen in humans. In addition to procedures for BSL-3, all personnel are required to work in full body pressure suits with their own air supply and are required to shower before departing. All materials leaving the laboratory must be decontaminated.
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