David Peat

Re-envisioning the Planet 175cient and powerful. As automobile engines became bigger, the problemof “knocking,” or pre-ignition of the gasoline/air mixture in theengine cylinders, became a major problem. For the engine to workefficiently, this mixture had to explode at just the right moment—whenit is ignited by the spark plug—so as to force down the piston and turnthe engine. But as an engine heats up, this mixture can also explodespontaneously producing a “knock” or backfire that reduces efficiency.The solution to the problem of knocking was discovered in 1921by Thomas Midgley who, not content with discovering Freon, alsofound that when a compound of lead is added to gasoline it preventspre-ignition. Thanks to Midgley’s discovery automobiles could becomebigger, faster, and more powerful. Two generations of motorists worldwidewould have thanked Midgley had they but known his name.Then, in the 1970s, scientists became concerned about the pollutionof the atmosphere from automobiles. Cities had banned the use ofsmoke-producing fuels for heating, and the age of Sherlock Holmes’sLondon fogs was past. But on hot days people now suffered from thechoking haze produced by car exhausts. One of these effluents was leadfrom gasoline, and experts wondered about the effects of prolongedexposure to low lead levels, particularly on young children. Some scientistsnow believe that lead pollution is responsible for the decline inIQs of American children born between 1950 and the 1980s (whenleaded gas began to be phased out for automobile use).Having discovered both Freon and leaded gas, it is no wonder thatMidgley is described by the author J. R. McNeil as having had “moreimpact on the atmosphere than any other single organism in earth’shistory.” 3DDTDDT was first synthesized during chemical research at the end of thenineteenth century, but its powerful effects as an insecticide were not3J. Robert McNeil. Something New Under the Sun: An Environmental History ofthe Twentieth-Century World (New York: Norton, 2001).