Environmental Engineering Reference
In-Depth Information
and other inorganic and organic chemicals is often insidious. Their probable car-
cinogenic, mutagenic, and teratogenic effects are extended in time, perhaps for
10, 20, or 30 years, to the point where direct causal relationships with morbidity
and mortality are difficult if not impossible to conclusively prove in view of the
many possible intervening and confusing factors. Nevertheless, sufficient informa-
tion about many noninfectious diseases, including the chronic diseases, is available
to make possible the mounting of an attack to prevent or at least minimize the
debilitating effects. Some will say that we do not have sufficient preventive infor-
mation and should devote our attention only to screening and treatment. Where
would we be today if the same philosophy prevailed in our attack on the infectious
diseases?
An interesting analysis was made by Dever
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for use in policy analysis of
health program needs. He selected 13 causes of mortality and allocated a percent-
age of the deaths, in terms of an epidemiologic model, to four primary divisions,
namely, system of health care organization, lifestyle (self-created risks), envi-
ronment, and human biology. He envisioned the environment as composed of a
physical, social, and psychological component. Environmental factors were con-
sidered to be associated with 9 percent of the mortality due to diseases of the
heart, with the rest due to causes associated with health care, life-style, or human
biology. Similarly, environmental factors were considered the cause of 24 percent
of the cancer deaths, 22 percent of the cerebrovascular deaths, and 24 percent of
the respiratory system deaths.
Of added interest is Dever's analysis showing that environmental factors were
considered to be the cause of 49 percent of all deaths due to accidents, 20 percent
of the influenza and pneumonia deaths, 41 percent of the homicides, 15 percent
of the deaths due to birth injuries and other diseases peculiar to early infancy, 6
percent of the deaths due to congenital anomalies, and 35 percent of the deaths
due to suicides.
There are an estimated 2 million recognized chemical compounds with more
than 60,000 chemical substances in past or present commercial uses. Approxi-
mately 600 to 700 new chemicals are introduced each year, but only about 15,000
have been animal tested with published reports. Limited trained personnel and
laboratory facilities for carcinogenesis testing in the United States by government
and industry will permit testing of no more than 500 chemicals per year. The
chemicals are viewed by Harmison
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as falling into four groups:
1. Halogenated hydrocarbons and other organics; polychlorinated biphenyls
(PCBs); chlorinated organic pesticides such as DDT, Kepone, Mirex, and
endrin; polybrominated biphenyls (PBBs); fluorocarbons; chloroform; and
vinyl chloride. These chemicals are persistent, often accumulate in food
organisms, and may in small quantities cause cancer, nervous disorders,
and toxic reactions.
2. Heavy metals: lead, mercury, cadmium, barium, nickel, vanadium, sele-
nium, beryllium. These metals do not degrade; they are very toxic and
may build up in exposed vegetation, animals, fish, and shellfish.
