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252 CHAPTER 5 PHYSIOLOGICAL AND TOXtCOLOGICAL CONSIDERATIONS

FIGURE 5.30 Comparison of ambient levels of I h maximum ozone, annual average of total sus-
pended participate matter (TSP), and sulfur dioxide in selected cities from around the world to illus-
trate the variation in these levels from country to country with respect to the United States.
41
[Reproduced from the National Air Quality and Emission Trends Report (1992), with permission.]

exposure to gas engine, especially diesel engine, exhausts. These individuals
are also at a larger than average risk of sudden death due to myocardial in-
farction, cardiovascular disease, and pulmonary disease. Several studies from
the U.S. and Europe have demonstrated that exposure to inhalable particles,
especially those generated by traffic and energy production, cause a one to five
percent increased risk of mortality among the general population. At the Eu-
ropean level, this would represent 50 000 to 100 000 additional deaths annu-
43 44
ally. ' It is probable that the previous examples of increased mortality
during historical air pollution episodes were largely due to exposure to small
particles. Unfortunately, no clear conclusions can yet be made concerning oc-
cupational dust exposure in general.

5.3.1.5 Concept of Risks
The term risk has wide implications. It is used to characterize difficulties
in predicting changes in the currency markets and to indicate the probability
of potential financial losses due to such changes. A surgeon prior to a major
operation also needs to evaluate the risks to the patient, not only due to the
disease, but also risks associated with the operation itself and the anesthesia.
Car drivers seldom consider the risk of a traffic accident when starting a car
even though the risk of a fatal car accident is many times greater than the cal-
culated risks associated with exposure to chemicals. Another example, widely
discussed in the media, is the comparison of risks from energy production by
fossil fuels and nuclear energy. This comparison has proven to be extremely
difficult due to a number of philosophical aspects. We can calculate with
some degree of certainty the risks involved in the production of energy with