Health hazard

A hazard is any agent that can cause harm or damage to life, health, property or the environment.

Hazards can be dormant or potential, with only a theoretical probability of harm. An event that is caused by interaction with a hazard is called an incident. The likely severity of the undesirable consequences of an incident associated with a hazard, combined with the probability of this occurring, constitute the associated risk. If there is no possibility of a hazard contributing towards an incident, there is no risk.

Identification of hazards is the first step in performing a risk assessment.

Kates (1978) defines environmental hazard as "the threat potential posed to man or nature by events originating in, or transmitted by, the natural or built environment". This definition includes a broader range of hazards ranging from long term environmental deterioration such as acidification of soils and build-up of atmospheric carbon dioxide to communal and involuntary social hazards such as crime and terrorism to voluntary and personal hazards such as drug abuse and mountain climbing. Environmental hazards usually have defined or common characteristics including their tendency to be rapid onset events meaning they occur with a short warning time, they have a clear source of origin which is easily identified, impact will be swift and losses suffered quickly during or shortly after on-set of the event, risk of exposure is usually involuntary due to location or proximity of people to set hazard and the "disaster occurs with an intensity and scale that justifies an emergency response" .

Hazards were grouped by Hewitt and Burton (1971) according to their characteristics. These were factors related to geophysical events which were not process specific. They were:

In defining hazard it is important to distinguish between natural hazards which may be defined as "extreme events that originate in the biosphere, hydrosphere, lithosphere or atmosphere" or "a potential threat to humans and their welfare" which include earthquake, landslide, hurricane and tsunamis and technological and man made hazards including explosions, release of toxic materials, episodes of severe contamination, structural collapses, and transportation, construction and manufacturing accidents etc. There is also a distinction to be made between rapid onset natural hazards, technological hazards and social hazards which are described as being of sudden occurrence and relatively short duration, and the consequences of environmental degradation such as desertification and drought, (McGuire, et al., 2002).

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