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250 CHAPTER 5 PHYSIOLOGICAL AND TOXICOLOGICAL CONSIDERATIONS

many cases, reduction of exposure will suffice to prevent many occupation-
related diseases after the first symptoms, but the exposure may also need to
be stopped completely. However, before such radical measures can be
taken, the association between the exposure and the disease has to be estab-
lished, i.e., the occupational nature of the disease needs to be demonstrated.
Therefore, occupational medicine relies on toxicological and occupational
hygienic knowledge in solving occupational health problems. However, the
scope of occupational medicine is much wider than simply examining
chemical-induced toxicity, as it covers a wide area of interests such as occu-
pational ergonomics and psychophysiological factors in the occupational
35
setting.
Poisoning Incidents in the Workplace
The hazards of chemicals are commonly detected in the workplace
first, because exposure levels there are higher than in the general environ-
ment. In addition, the exposed population is well known, which allows
early detection of the association between deleterious health effects and
the exposure. The toxic effects of some chemicals, such as mercury com-
pounds and soot, have been known already for centuries. Already at the
end of the eighteenth century, small boys who were employed to climb up
the inside of chimneys to clean them suffered from a cancer of the scrotum
due to exposure to soot. This was the first occupational cancer ever identi-
fied. In the viscose industry, exposure to carbon disulfide was already
known to cause psychoses among exposed workers during the nineteenth
century. As late as the 1970s, vinyl chloride was found to induce angiosar-
coma of the liver, a tumor that was practically unknown in other in-
stances. 36
Even in the Nordic countries, exposure to carbon disulfide still caused
severe central nervous effects among exposed workers during the late 1960s
and early 1970s, and exposure to lead caused several lead poisonings at the
same time. Exposure to asbestos remained a major health hazard until the
1970s. The use of asbestos is nowadays strictly controlled and it has been
banned in many countries. Nevertheless, it continues to be an important oc-
cupational health problem because of the long latency period of asbestos for
causing lung cancer and mesothelioma, a time period of 20-40 years. In ad-
dition, there are large amounts of asbestos remaining in buildings, and reno-
vation of old buildings will pose a health risk to workers for a long time to
come. 37
Many very hazardous solvents, such as benzene and carbon tetrachloride,
were widely used until the 1970s. The situation was very similar for the use of
pesticides. Among the toxic pesticides that were still in wide use 20 years ago
were chlorophenols, DDT, lindane, and arsenic salts, all of which are classified
4 38
as human carcinogens as well as being acutely toxic. ' Fortunately, use of
these kinds of very toxic chemicals is now limited in the industrialized world.
However, because the number of chemicals used in various industries contin-
ues to increase, the risks of long-term health hazards due to long-term expo-
sure to low concentrations of chemicals continues to be a problem in the
workplace.