Urban Air Pollution - Air Pollution and Global Warming: History, Science, and Solutions - page 80

Figure 4.4. Noontime photograph of Donora, Pennsylvania, on October 29, 1948, during a deadly smog event.
Copyright Photo Archive/Pittsburgh Post-Gazette, 2001. All rights reserved. Reprinted with permission.

from steel mills and metal fumes from the Donora Zinc
Works, a zinc smelter, under a strong temperature inver-
sion resulted in the deaths of 20 people and 10 dogs,
as well as the respiratory illness of 7,000 of the town's
14,000 human residents. Of the 20 people who died, 14
had a known heart or lung problem. Both young and old
people became ill, and most of the illnesses arose by
the third day. Symptoms included cough, sore throat,
chest constriction, shortness of breath, eye irritation,
nausea, and vomiting. A sample of 229 dogs and 165
cats after the event found that 15.5 percent of dogs and
7.3 percent of cats suffered illness (Catcott, 1955). The
smog event darkened the city during peak daylight hours
(Figure 4.4).
During the 1940s and 1950s, the darkening of cities
throughout the United States and Europe during the
day due to factory smoke and vehicle exhaust was not
unusual (e.g., Figure 4.5). This unabated air pollution
shortened the lives of city dwellers by several years,
contributed to millions of illnesses and hundreds of
thousands of premature deaths per year, as well as a
general feeling of helplessness among those trapped
under the pollution.

in sunny regions gained additional notoriety in the twen-
tieth century. Most prominent was a layer of pollution
that formed almost daily over Los Angeles, California.
In the early twentieth century, this layer was caused by
a combination of directly emitted smoke (London-type
smog) and chemically formed pollution called photo-
chemical smog . Sources of the smoke were primarily
particles from fuel combustion in factories and power
plants and from the open burning of waste. Sources of
the chemically formed pollution were primarily gases
from factory and automobile emissions. In 1903, the
factory smoke was so thick that one day, residents of Los
Angeles believed that they were observing an eclipse of
the sun (South Coast Air Quality Management District
(SCAQMD), 2011). Between 1905 and 1912, regula-
tions controlling smoke emissions were adopted by the
Los Angeles City Council. However, such regulations
were of little benefit, as illustrated by Figure 4.6, which
shows clouds of dark smoke billowing out of stacks and
traveling across the city.
As automobile use increased, the relative fraction of
photochemical versus London-type smog in Los Ange-
les increased between the 1910s and 1940s. From 1939
to 1943, visibility in Los Angeles declined precipi-
tously. On July 26, 1943, a plume of pollution engulfed
downtown Los Angeles, reducing visibility to three
blocks. Even after a local Southern California Gas Com-
pany plant suspected of releasing butadiene gas was shut

4.1.7. Photochemical Smog
Although short, deadly air pollution episodes have
attracted public attention, persistent pollution problems