Page 300 - Industrial Ventilation Design Guidebook

256 CHAPTER 5 PHYSIOLOGICAL AND TOXICOLOGICAL CONSIDERATIONS

Seveso, Italy, caused wide-spread pollution of the industrial site as well as its
surroundings. Serious effects of dioxin were detected both in domestic animals,
such as cows and sheep, and in humans, the most serious early effects being a
serious skin disease, chloracne, and alterations in the function of the immune
system. Follow-up studies have demonstrated that this accident also increased
the cancer risk in exposed individuals. 51
Outdoor inhalation exposure is mainly due to traffic, energy production,
heating, and natural factors such as pollen and mineral dusts. These outdoor
sources of pollution also affect indoor air quality. The indoor concentration is
typically 20-70% of the corresponding outdoor concentration. Occasionally
the indoor concentrations of an external pollutant (especially radon) may even
exceed the concentrations outdoors. 41
In densely populated areas, traffic is responsible for massive exhausts of ni-
trous oxides, soot, polyaromatic hydrocarbons, and carbon monoxide. Traffic
emissions also markedly contribute to the formation of ozone in the lower parts
of the atmosphere. In large cities, fine particle exposure causes excess mortality
43
which varies between one and five percent in the general population. Con-
tamination of the ground water reservoirs with organic solvents has caused con-
cern in many countries due to the persistent nature of the pollution. A total
exposure assessment that takes into consideration all exposures via all routes is
52 5
a relatively new concept, the significance of which is rapidly increasing. ' '
Characteristics of Industrial Processes
The in-plant emissions can be divided into process and manual emissions.
In the process industry, the emission sources can usually be enclosed and the
workers do not need to stay for long periods close to the emissions. The emis-
sions are minor, and even if they do occur, they are generally released far from
the areas where workers have their accommodation. Often, workers can
spend most of their time in clean control rooms. In certain process industries,
such as the petrochemical industry, the processes are located largely outdoors,
and the emissions are mainly fugitive emissions from leaking seals of flanges,
valves, and pump shafts. Manual emissions occur in the immediate vicinity of
the worker due to the task he or she is performing. Typical examples include
welding, painting, gluing, sawing, and grinding. It is natural that the exposure
control is much easier for process emissions than for manual ones. Even very
toxic substances can be used safely in the process industry whereas even mod-
erately noxious chemicals may cause major problems in manual tasks. Thus,
avoidance of those manual tasks with chemicals known to cause adverse
health effects is important. If the automation of these tasks becomes very ex-
pensive, it may be possible to use subcontractors who specialize in this kind of
work and have adequate control arrangements in their production facilities.
The best way to control exposure is to replace dangerous agents with
safer ones. Today, highly toxic solvents, such as benzene, bromobenzene, car-
bon tetrachloride, and chloroform are no longer extensively used. Benzene re-
mains, however, an important chemical in the petrochemical industry, but the
processes where it is used are closed.
The use of other highly toxic substances, such as lead and carbon disul-
fide, which have in the past caused many occupational diseases, is also rare in