Structure and Composition of the Present-Day Atmosphere - Air Pollution and Global Warming: History, Science, and Solutions - page 68

people more susceptible to allergic response to indoor
allergens (Jones, 1999). At mixing ratios much higher
than normal indoor or outdoor conditions, NO 2 (g) can
result in acute bronchitis (25-100 ppmv) or death (150
ppmv).

3.6.9. Lead
Lead [Pb(s)] is a gray-white, solid heavy metal with
alow melting point that is present in air pollution as
an aerosol particle component. It is soft, malleable, a
poor conductor of electricity, and resistant to corrosion.
It was first regulated as a criteria air pollutant in the
United States in 1977. Many countries now regulate the
emission and outdoor concentration of lead. Neverthe-
less, lead poisoning, particularly in children, is still a
pervasive problem in many countries of the world.

3.6.9.1. Sources and Sinks
Table 3.14 summarizes the sources and sinks of atmo-
spheric lead. Lead is emitted during combustion of vehi-
cle fuel containing a lead additive, manufacture of lead
acid batteries, crushing of lead ore, condensation of
lead fumes from lead ore smelting, solid waste disposal,
uplift of lead-containing soils, and crustal weathering
of lead ore. Between the 1920s and 1970s, the largest
source of atmospheric lead was vehicle combustion.
In December 1921, General Motors researcher
Thomas J. Midgley, Jr .(1889-1944) (Figure 3.16)
discovered that adding tetraethyl lead to fuel reduced
automobile engine knock, increased octane levels, and
increased engine power and efficiency. Midgley later
discovered chlorofluorocarbons (CFCs), the precursors
to stratospheric ozone destruction (Section 11.5.1).

Figure 3.16. Thomas J. Midgley, Jr. (1889-1944).
Inventor of leaded gasoline and chlorofluorocarbons
(CFCs), Midgley was born in Beaver Falls,
Pennsylvania, in 1889. He grew up in Dayton and
Columbus, Ohio, and graduated from Cornell
University with a degree in mechanical engineering in
1911. In 1916, he joined the Dayton Engineering
Laboratories Company (DELCO) as a researcher.
DELCO became the main research laboratory for
General Motors in 1919. In 1921, Midgley invented
leaded gasoline, which he named ethyl. In 1923, he
became vice president of the Ethyl Gasoline
Corporation, a subsidiary of General Motors and
Standard Oil. In 1924, he was forced to step down
due to management problems. He returned to
research on synthetic rubber at the Thomas and
Hochwalt Laboratory in Dayton, Ohio, with funding
from General Motors. In 1928, Midgley and two
assistants invented CFCs as a substitute refrigerant
for ammonia. Midgley moved on to became vice
president of Kinetic Chemicals, Inc. (1930); director
and vice president of the Ethyl-Dow Chemical
Company (1933); and director and vice president of
the Ohio State University Research Foundation
(1940-1944). In 1940, he became afflicted with polio,
causing him to lose a leg and design a system of
ropes to pull himself out of bed. On November 2,
1944, he died of strangulation in the rope system,
possibly by suicide. Edgar Fahs Smith Collection,
University of Pennsylvania Library.

Table 3.14. Sources and sinks of atmospheric lead

Sources Sinks

Leaded fuel combustion in
transportation vehicles
Lead acid battery
manufacturing

Deposition to oceans, sea
ice, snow, soil, and
vegetation
Inhalation

Lead ore crushing and
smelting
Dust from soils
contaminated with
lead-based paint
Solid waste disposal
Crustal physical weathering