Page 295 - Industrial Ventilation Design Guidebook

5.3 TOXiCITY AND RISKS INDUCED BY OCCUPATIONAL EXPOSURE TO CHEMICAL COMPOUNDS 25 I

Association of Industrial Activity and Poisonings
in the General Environment
The harmful effects of industrial emissions are not confined to the work-
ers but extend beyond the plant boundary line. Chemically-induced diseases
among workers exposed to industrial chemicals are a warning sign of the risks
to which a larger population is also being exposed; usually the chemical haz-
ards are in principle similar in the occupational and general environment.
However, occasionally environmental exposures can be qualitatively different
from the occupational environment and may also cause deleterious health ef-
39 40
fects in the general population. '
Since the general population is much larger than the occupationally ex-
posed worker groups, and also includes very sensitive individuals, some del-
eterious effects have been detected only in the general population. Urban air
pollution is a good example. In the 1930s, an air pollution incident in the
valley of the River Maas in Belgium was responsible for the deaths of tens of
individuals due to increased concentrations of coal dust and sulfur dioxide
in the ambient air. At that time, it was already predicted that this could be a
harbinger of future catastrophes in a major city like London, and, indeed, in
1952, a dramatic increase of concentrations in small coal particles and sul-
fur dioxide took place during weather inversion in the London metropolitan
area. In consequence, an excess mortality of more than 4000 individuals oc-
curred during a few days. Similar though less severe smogs (a fog caused by
air pollution) took place in the late 1950s. Subsequently the use of coal was
prohibited in London and today the air quality in the city is much better
than it was 40 years ago. In addition to this classic kind of smog, photo-
chemical smog, consisting of nitrous oxides and ozone and their reaction
products with hydrocarbons, is encountered in warm and sunny areas where
there is major traffic-related pollution. A model area for such a situation is
Los Angeles, California, where the air quality is a continuous concern. 41
The emphasis on air pollution in different parts of the world has led to
marked improvements in air quality. However, there are several metropolitan
areas in the world where the air pollution situation is still deteriorating. Ex-
amples of such areas are Mexico City, Mexico, New Delhi, India, Cairo,
Egypt, and Sao Paulo, Brazil. Most of these badly polluted areas are in devel-
oping countries where resources for improving the situation are limited. Thus,
these problems are difficult to solve (see Fig. 5.30). 41
Recently, much emphasis has been put on the harmful effects of small par-
ticles, i.e., particulate matter (PM), on human health. A number of standards
have been established to characterize the PM fractions in the air and their ef-
fects on human health. A widely used PM standard in force in both Europe
and the United States is based on the mass concentration of particles with a di-
ameter of 10 JJUTI or less (PM 10). However, recently the U.S. Environmental
Protection Agency (EPA) proposed a new standard that is based on the aero-
dynamic diameter of 2.5 u,m particles. This new standard emphasizes the sig-
nificant impact of small particles on human health, especially on the
41 42
respiratory and cardiovascular systems. '
It has been known for years that professional bus and truck drivers as well
as railroad workers suffer a larger than average risk of lung cancer because of