Describing environmental exposure to hazards

To reduce the adverse impacts of environmental hazards on human health you need to understand where the hazard comes from, identify it and the pathway it can take to affect people.

The source of the hazard is the place of origin from proposed and existing activities. Patients and carriers discharge infectious agents (biological hazards) that could infect healthy people. Industrial processes in a factory release chemical hazards that may be found in sewage; the sewage could reach drinking water, thereby creating the possibility of ingesting these chemicals. Household activities could also be sources of hazards, for example, cooking with fuels such as animal dung and charcoal produces toxic smoke that can cause lung diseases.

The type of hazard is the particular chemical, infectious agent or other agent involved. The pathway is the route by which the hazard gets from the source to the person.

The response or the effect is the health outcome (changes in body function or health) after the hazard has affected the person. The amount and type of change (or response) depends on the type of hazard and the effect it can have on different people. This would depend on the person's individual health and factors such as their age; for example, young children or people who are already sick are often more harmed by diseases such as diarrhoea than healthy adults.

If you want to prevent a hazard, you need to understand the source of the hazard (where it comes from), the type of hazard (for example the type and concentration of a chemical), the pathway (the affected environment and how the exposure could take place), and the response (the effect the hazard could have on people).

We will demonstrate this with an example. Sewage containing cadmium (a toxic chemical) is produced by a hide-processing factory and flows into a river. People downstream of the point of discharge drink the contaminated water and become sick. The hazard exposure is described as follows:

• The source is sewage from a factory.
• The type of hazard is chemical, in this case cadmium.
• The pathway or affected environment is the river that is used by the public as a source of drinking water and the exposure took place by swallowing/ ingesting the chemical with drinking water. In addition, any fish contaminated with cadmium may have been eaten.
• The response is that people who consumed the contaminated water and fish had symptoms of cadmium poisoning (i.e. joint and spinal pains, pains in the abdomen) and they complained to a health centre.