(Created 12/02)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
(Revised 1/03)
TOXICOLOGY AND EXPOSURE GUIDELINES
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(For assistance, please contact EHS at (402) 472-4925, or visit our web site at
http://ehs.unl.edu/
)
"All substances are poisons; there is none which is not a poison. The right dose differentiates a
poison and a remedy."
This early observation concerning the toxicity of chemicals was made by Paracelsus (1493-
1541). The classic connotation of toxicology was "the science of poisons."
Since that time, the
science has expanded to encompass several disciplines. Toxicology is the study of the interaction
between chemical agents and biological systems. While the subject of toxicology is quite
complex, it is necessary to understand the basic concepts in order
to make logical decisions
concerning the protection of personnel from toxic injuries.
Toxicity can be defined as the relative ability of a substance to cause adverse effects in living
organisms. This "relative ability is dependent upon several conditions. As Paracelsus suggests,
the quantity or the dose of the substance determines whether the effects
of the chemical are toxic,
nontoxic or beneficial. In addition to dose, other factors may also influence the toxicity of the
compound
such as the route of entry, duration and frequency of exposure, variations between
different species (interspecies) and variations among members of the same species (intraspecies).
To apply these principles to
hazardous materials response, the routes by which chemicals enter
the human body will be considered first. Knowledge of these routes will support the selection of
personal protective equipment and the development of safety plans.
The second section deals
with dose-response relationships. Since dose-response information is available in toxicology and
chemistry reference books, it is useful to understand the relevance
of these values to the
concentrations that are actually measured in the environment. The third section of this chapter
includes the effects of the duration and frequency of exposure, interspecies variation and
intraspecies variation on toxicity. Finally, toxic responses associated
with chemical exposures
are described according to each organ system.
