Page 30 - Fundamentals of Air Pollution 3E

III. The Twentieth Century 9

At the start of this period, steam locomotives came into the heart of the
larger cities. By the end of the period, the urban terminals of many railroads
had been electrified, thereby transferring much air pollution from the rail-
road right-of-way to the electric generating station. The replacement of coal
by oil in many applications decreased ash emissions from those sources.
There was rapid technological change in industry. However, the most
significant change was the rapid increase in the number of automobiles
from almost none at the turn of the century to millions by 1925 (Table
1-1).
The principal technological changes in the engineering control of air
pollution were the perfection of the motor-driven fan, which allowed large-
scale gas-treating systems to be built; the invention of the electrostatic
pretipitator, which made particulate control in many processes feasible;
and the development of a chemical engineering capability for the design
of process equipment, which made the control of gas and vapor effluents
feasible.

B. 1925-1950
In this period, present-day air pollution problems and solutions emerged.
The Meuse Valley (Belgium) episode (4) occurred in 1930; the Donora,
Pennsylvania, episode (5) occurred in 1948; and the Poza Rica, Mexico,
episode (6) in 1950. Smog first appeared in Los Angeles in the 1940s (Fig.
1-5). The Trail, British Columbia, smelter arbitration (7) was completed in
1941. The first National Air Pollution Symposium in the United States was
held in Pasadena, California, in 1949 (8), and the first United States Techni-
cal Conference on Air Pollution was held in Washington, D.C., in 1950 (9).
The first large-scale surveys of air pollution were undertaken—Salt Lake
City, Utah (1926) (10); New York, New York (1937) (11); and Leicester,
England (1939) (12).
Air pollution research got a start in California. The Technical Foundation
for Air Pollution Meteorology was established in the search for means
of disseminating and protecting against chemical, biological, and nuclear
warfare agents. Toxicology came of age. The stage was set for the air
pollution scientific and technological explosion of the second half of the
twentieth century.
A major technological change was the building of natural gas pipelines,
and where this occurred, there was rapid displacement of coal and oil as
home heating fuels with dramatic improvement in air quality; witness the
much publicized decrease in black smoke in Pittsburgh (Fig. 1-6) and St.
Louis. The diesel locomotive began to displace the steam locomotive,
thereby slowing the pace of railroad electrification. The internal combustion
engine bus started its displacement of the electrified streetcar. The automo-
bile continued to proliferate (Table 1-1).