Biological hazards

A microbiological laboratory where workers may be exposed to biological hazards while handling microorganisms. The door is marked with a “Biohazard” sign. ^{© G. Tjalvin}

A biological hazard refers to any microorganism, cell, or organic material of plant, animal, or human origin, including genetically modified organisms, that can harm human health. This encompasses bacteria, viruses, parasites, fungi, prions, DNA materials, bodily fluids, and other microorganisms, along with their associated allergens and toxins. Health impacts can range from infectious and non-infectious diseases to injuries. In the workplace, biological hazards also include vectors or transmitters of disease.

Biological hazards can be divided into contagious and non-contagious categories based on their ability to spread from person to person.

Contagious biological hazards

These are biological agents that can be transmitted from one individual to another, either directly or indirectly. Typical examples of contagious microorganisms include bacteria, viruses, fungi, and parasites. While microorganisms are a normal part of our environment and most pose no threat to our health, some can be harmful depending on the organism’s characteristics, the amount present, and human susceptibility. Human susceptibility varies based on how biological factors enter the body and the body’s ability to defend itself. Our ability to protect ourselves is lower among elderly individuals, during sickness, severe injuries, and periods of immunodeficiency. Protection is also decreased with open wounds, eczematous skin, and lack of preventive measures such as gloves, suits, respiratory protection, or vaccinations.

Workers in a waste disposal facility can easily come into contact with materials contaminated by body fluids, suffer cuts, or be pricked by needles. This exposure can lead to contact with biological agents, potentially resulting in diseases such as hepatitis B, hepatitis C, and HIV. ^{© Colourbox}

The most common infectious sources in workplaces are:

• Patients suffering from a contagious disease
• Stool, blood, saliva, and other body fluids from infected humans or animals
• Healthy carriers of an infectious disease who are not ill themselves
• Work processes producing dust, droplets, and aerosols containing a range of microorganisms
• Work processes where microorganisms may contaminate instruments, tools, or facilities

Spreading of Infectious Diseases

Workers may develop infections through both direct and indirect contact with infectious agents.

Direct Contact

• Person-to person contact. Spread of infectious agents by skin or mucous membrane contact, including blood or other body fluids, and transmission of infectious diseases via placenta in pregnant workers. Examples: Skin infections due to Staphylococcus aureus, Ebola.
• Droplets spread containing infectious agents. Due to their size, these droplets travel only a short vertical distances (less than a metre) from the infected person before falling down. Example: Rubella, COVOD-19.

Indirect Contact

• Airborne transmission. Droplets evaporate quickly, but the microorganisms can stay airborne for a long time. Due to their tiny size, small particle aerosols can travel long distances on air currents and remain suspended in the air for minutes to hours and can infect anyone who breaths the contaminated air. Example: Tuberculosis.
• Contaminated objects including needles, syringes and contaminated blood products, surfaces and materials. Examples: HIV infection, hepatitis B and C due to needle stick injuries, Ebola.
• Food and drinking water.
• Animal-to-person contact. Infectious disease due to bites or scratches by an infected animal, or handling of animal waste.
• Zoonosis. Example: Anthrax (from sheep) in farmers and veterinarians.
• Soil, water and vegetation containing infectious organisms. Examples: Toxoplasmosis in cat feces. Legionella spread due to aeration of water by cooling towers.

Non-contagious biological hazards

Non-contagious biological hazards are biological materials that do not spread from person to person but can still pose significant health risks. Examples include non-pathogenic live or dead bacteria as well as fungi, viruses, high molecular weight allergens, bacterial endotoxins and biotoxins.

Bagging coffee husk material, a byproduct of coffee production, can lead to significant exposure to organic dust and endotoxins. ^{© B.E. Moen}

An allergen is a substance that can trigger an allergic reaction in some people. When an allergen enters the body, the immune system may mistakenly identify it as harmful and induce an immune response. This immune response may lead to allergy symptoms, which can range from mild (like sneezing and itching) to severe (such as anaphylaxis).

An endotoxin is a toxic substance that is part of the outer membrane of Gram-negative bacteria. These toxins are released when the bacterial cell disintegrates, and they can trigger strong immune responses in humans.

A biotoxin is a toxic substance produced by living organisms, such as plants, animals, fungi, or bacteria. Tetanus toxin is an example. It is a potent neurotoxin produced by the bacterium Clostridium tetani.

According to ILO the following biological agents and infectious or parasitic diseases should be considered as being occupational: Brucellosis, Hepatitis viruses, Human immunodeficiency virus (HIV), Tetanus, Tuberculosis, toxic or inflammatory syndromes associated with bacterial or fungal contaminants, Anthrax and Leptospirosis. See the ILO list of Occupational Diseases (2010)