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332 CHAPTER 5 PHYSIOLOGICAL AND TOXICOLOGICAL CONSIDERATIONS

and the general population. It simply means that the nature of exposures and their
consequences have changed; rather than causing acute poisonings, exposures in
these societies cause long-term effects such as allergies, cancers, and other chronic
diseases such as cardiovascular diseases and asthma. The risk assessment of long-
term effects of chemical exposures is much more demanding than assessing the
49 180 201 204
risks of deterministic effects due to high exposures. ' ' "
In developing countries, exposure to chemicals, e.g., pesticides, is respon-
sible for millions of acute poisoning cases and hundreds of thousands of fatal-
203
ities every year. This is due to the low standard of living, poor education,
failure to appreciate the significance of hygienic measures and the effects of
the compounds, and general attitudes. Furthermore, most developing coun-
tries are situated in subtropical or tropical areas where the use of a number of
chemicals, such as pesticides, is a necessity. Thus, inadequate safety measures,
regulations, and education easily lead to careless use of highly toxic com-
pounds. Much can be done to alleviate this situation, e.g., experts can visit to
highlight problems in these countries, but ultimately the situation can only be
improved by measures in each country. These measures will include improved
education and increased awareness of the toxicity of the compounds and ap-
propriate safety measures.
A good example is the accident that took place in Bhopal, India, in 1984.
An explosion in a pesticide plant producing carbaryl, a highly toxic insecti-
cide, caused a release of the raw material of the pesticide, methyl isocyanate,
into the environment. In all, 10-25 tons of this highly toxic and reactive com-
pound were released into the densely populated area surrounding the plant.
The LC 50 value (concentration that kills 50% of the exposed experimental
animals) of the gas is 10-30 ppm. In the Bhopal region, the exposure resulted
in 5000 deaths and 100 000 less severe poisonings, with 5000 persons suffer-
ing permanent damage to their respiratory systems. 41

5.3.6.3 Perception of Risks by Experts and the General Population
Communication of risks to the general public is extremely important for
policy-making in consideration of toxic substances. Policy makers should be
able to educate the public concerning the differences between different
chemical hazards, and that the magnitude of the exposure and thus the dose
is essential for assessing the magnitude of the risk. The existence of a chemi-
cal hazard does not imply as such a risk to human populations. However,
risk communication is usually a difficult task because the concept of risk is
so difficult to understand, and, especially in a crisis, failure in risk communi-
cation is the rule rather than the exception. Several investigators have exten-
sively studied risk perception and risk communication between lay people
and experts. They have found marked differences in the perception of risks
between these groups. Especially among the lay people, the familiarity of the
risk (e.g., occupational exposure vs. smoking), the magnitude of the out-
come of the risk (release of a chemical in the workplace vs. car accident),
and the severity of the outcome of an event (release of minute amounts of ra-
don within a nuclear plant vs. fire) all have a major impact on the perception
49
of risks (see Fig. 5.58). Alcohol consumption is a good example. Con-
sumption of ethyl alcohol is one of the most important health hazards in in-