Page 423 - Fundamentals of Air Pollution 3E

III. Conversion of Physical Data and Criteria to Standards 375

costs and air quality standards. This argument certainly does hold with
respect to the soiling of materials and structures. In fact, it is frequently
the protective coatings themselves that require replacement because they
become dirty long before their useful life as protectants has terminated. It
can readily be shown that there are costs associated with soiling, including
the cost of removing soil, the cost of protective coatings to facilitate the
removal of soil, the premature disposal of material when it is no longer
economical or practicable to remove soil, and the growth inhibition of
vegetation due to leaf soiling. However, decision making for air quality
standards related to soiling is based less on economic evaluation than on
aesthetic considerations, i.e., on subjective evaluation of how much soiling
the community will tolerate. This latter determination is judgmental and
difficult to make. It may be facilitated by opinion surveys, but even when
the limit of public tolerance for soiling is determined, it still has to be
restated in terms of the pollution loading of the air that will result in this
level of soiling.
An important effect of air pollution on the atmosphere is change in
spectral transmission. The spectral regions of greatest concern are the ultra-
violet and the visible. Changes in ultraviolet radiation have demonstrable
adverse effects; e.g., a decrease in the stratospheric ozone layer permits
harmful UV radiation to penetrate to the surface of the earth. Excessive
exposure to UV radiation results in increases in skin cancer and cataracts.
The worldwide effort to reduce the release of stratospheric ozone-depleting
chemicals such as chlorofluorocarbons is directed toward reducing this
increased risk of skin cancer and cataracts for future generations.
The fact that after a storm or the passage of a frontal system the air
becomes crystal clear and one can see for many kilometers does not give a
true measure of year-round visibility under unpolluted conditions. Between
storms, even in unpolluted air, natural sources build up enough particulate
matter in the air so that on many days of the year there is less than ideal
visibility. In many parts of the world, mountains are called "Smoky" or
"Blue" or some other name to designate the prevalence of a natural haze,
which gives them a smoky or bluish color and impedes visibility. When
the Spanish first explored the area that is now Los Angeles, California,
they gave it the name "Bay of the Smokes." The Los Angeles definition
of air quality before the advent of smog was that "You could see Cata-
lina Island on a clear day." The part of the definition that is lacking is
some indication of how many clear days there were before the advent
of smog.
There are costs associated with loss of visibility and solar energy. These
include increased need for artificial illumination and heating; delays, dis-
ruptions, and accidents involving air, water, and land traffic; vegetation
growth reduction associated with reduced photosynthesis; and commercial
losses associated with the decreased attractiveness of a dingy community