The Science:

The UK Health and Safety Commission (as cited in Aw & Harrison, 1998) and the US Center for Disease Control and Prevention (CDC, 2009) define biological hazards as “infectious agents or products of such agents that cause human disease,” and biological agents as “any microorganism, cell culture, or human endoparasite, including any which have been genetically modified, which may cause any infection, allergy toxicity, or otherwise create a hazard to human health.” (Newman-Martin, 2012, p. 12).

Biological agents can be classified in several ways. Occupational Hygienists tend to categorise according to biological type, as follows: 

• Bacteria 

• Fungi 

• Viruses

• Parasites 

• Toxins 

• Allergens 

Micro-organisms can enter the human body via four routes of entry: through inhalation of airborne micro-organisms, by micro-organisms entering the skin via injection and absorption, and through ingestion – swallowing micro-organisms. (Crawford, 2015, pp. 2-3)

Risk Potential:

Exposure to biohazards Workers can be exposed to biohazards in the following ways:

• Host to host

• Air (bioaerosol)

• Water and food

• Vectors

Micro-organisms can enter the human body via four routes of entry:

• through inhalation of airborne micro-organisms,

• by micro-organisms entering the skin via injection and absorption, and

• through ingestion – swallowing micro-organisms.

The level of risk is dependent on a number of factors including: 

• Toxicity of the substance 

• The dose the worker is exposed to 

• The duration of exposure 

• The route of exposure (inhaled, absorbed through skin or mucous membranes, ingested) 

• The personal characteristics of the exposed worker (age, gender, general health, etc.) 

• Environmental factors (e.g. temperature, air flow)

Risks from infectious biohazards also depend on the substances virulence, its ability to survive outside the human body. Tetanus spores are an example of strong virulence, as spores can survive in the soil for long period.

Two factors that impact the effect of a biological hazard are dose and the host. The dose measurement for micro-organisms is similar to that of a toxic chemical (concentration x duration of exposure) and workers can experience either an acute or chronic exposure. Individual differences of the worker (the host) and the surrounding environment can modify toxic effects.  

The environment in which the toxic exposure takes place also plays a significant part in determining the amount of toxin the organism (the worker) is exposed to.

(Crawford, 2015, pp. 3-5).

Measurement and evaluation:

Once the potential hazard has been recognized you should:

1. Measure the worker’s actual exposure to the hazard.

2. Compare the results with an acceptable standard. 

3. Make a decision as to whether the worker’s health or safety is being placed at risk. 

Engage an occupational hygienist.

(Crawford, 2015, p. 8)