hazards are things found in air, water, and soil that negatively
impact living beings. These health hazards are assessed in terms
of dose-response, exposure and risk.
the Swiss physician and alchemist, the "father" of modern
toxicology (1493 1541) said, "The dose makes the poison."
In other words, for most toxic substances, the amount of a substance
a person is exposed to is as important as how toxic the substance
might be. For example, small doses of aspirin can be beneficial
to people, but at very high doses, this common medicine can be lethal.
Individual responses to dose often vary. Even in very low doses,
aspirin is deadly for some people.
can be exposed to environmental hazards in three ways:
through the skin
(entry through the respiratory system)
- Entry through
the mouth and digestive system
substances are more likely to be absorbed into the body by one means
of exposure than by another. Knowing how a hazardous substance is
likely to enter the body aids in assessing our potential for exposure.
hazards are often characterized by the risk they pose to human health
as well as by their effects on our environment. Risk is assessed
by the combined effect of the toxicity of the substance and the
amount of exposure. At least some exposure and some toxicity are
required to result in a risk. For example, if your exposure to a
non-toxic substance is high, there is no risk. By the same token,
if the substance is very toxic but no one is exposed to it, there
is no risk. Thus -
RISK = TOXICITY x EXPOSURE
It is very
important to be aware of how to minimize the risks of environmental
health hazards. In the following lessons, we will talk about
hazards and how to avoid them.