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Midgley, Thomas
(1889-1944)
American chemist

Thomas Midgley was a brilliant industrial chemist and had more impact on the atmosphere than any other single organism in the history of life on earth.

Midgley was born 18 May 1889 in Beaver Falls, Pennsylvania. He studied engineering at Cornell University and learned chemistry on his own. In 1916 he joined the laboratory of Charles Kettering in Dayton, Ohio, sponsored by the General Motors Research Corporation, where he sought additives for gasoline that would reduce ‘knocking’ and thereby allow higher-compression engines. In late 1921 he found that lead did the job admirably. Soon tetraethyl lead became a standard gasoline additive, first in the United States and eventually around the world.

A public health controversy arose in 1924, and lead gasoline was briefly withdrawn from the U.S. market. But by 1926 authorities found the risk acceptable. Thereafter, millions of tons of lead entered the atmosphere with vehicle exhausts, some of which found its way into plant and animal tissues, and into human bodies, where, in sufficient doses, it caused disorders in nervous systems and brains, especially those of children. Ambient lead derived from several sources, but mainly from vehicle exhausts. Most countries phased out leaded gasoline gradually in the late twentieth century, and ambient lead concentrations dropped dramatically, as did the lead levels in human bloodstreams.

In the late 1920s Midgley took up research on refrigerants. At that time, chemical refrigeration involved dangerous gases, such as ammonia. Midgley in 1930<N>31 developed the first of the chlorofluorocarbons, Freon (dichlorofluoromethane), an inert gas that made safe refrigeration feasible and air-conditioning practical. Chlorofluorcarbons (CFCs) also proved useful in solvents, spray propellants, and insulation.

CFC production remained small until after World War II, but by 1970 some 750,000 tons of CFCs entered the atmosphere annually. They drifted up to the stratosphere intact (because as inert gases they react with very few chemicals), where ultraviolet radiation broke up CFC molecules, releasing agents that in turn ruptured ozone molecules. Stratospheric ozone has for roughly a billion years formed a shield that minimizes the amount of ultraviolet-B radiation reaching the earth’s surface, making life as it has evolved possible. Enhanced UV-B radiation endangered phytoplankton (the basis of the oceans’ food web), human immune systems, and raised skin cancer rates. By the year 2000, perhaps two million excess cases of skin cancers were attributable to the thinning of the ozone shield.

In the 1970s scientists suggested that CFCs might erode the ozone layer, and in the 1980s careful measurements showed this had indeed happened. International agreements followed quickly, limiting further CFC production. But, as inert gases, CFCs linger in the atmosphere for about a century, so that some of those released in the twentieth century will still be rupturing ozone molecules late in the twenty-first century.

Midgley won most of the prizes an industrial chemist can win in the U.S. and became president of the American Chemical Society. He died in 1944, strangled by the ropes of a rope-and-pulley system he had invented to help him in and out of bed after he contracted polio.

J. R. McNeill

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