3. Leaded gasoline in the United States created high levels of lead in the food supply
In the 1920s, as the internal combustion engine began to require greater levels of power to move the increasingly heavy automobiles being produced at the higher rates of speed demanded by an enthusiastic motoring public, engineers at Dayton Engineering Laboratories in Ohio arrived at a novel solution. Though lead was known to be a poison and its dangers were well documented, its addition to gasoline to increase octane levels and decrease engine knock began in 1923 and continued for over fifty years. The result was toxic levels of lead in the atmosphere, which leached into agricultural soil and the water supply. By the 1950s the neurotoxin was prevalent everywhere, yet Americans continued to blithely pump lead into the environment, reassured by studies which declared the additive to be harmless, nearly all of which were funded by General Motors, owner of the company which manufactured it.
In the 1970s actions to clean up the environment led to the removal of leaded gasoline, though some aviation fuels continue to use it, and all gasoline available at the pump became lead free. Forty years later excessive amounts of lead were still present in many soil surveys, though they have been reduced. Social scientists and criminologists also noted a decrease in violent crime of all types, a trend which began about two decades following the removal of lead from gasoline. Tetraethyl lead, (TEL) was patented and sold to gasoline producers for more than fifty years despite the same benefits being available from ethyl alcohol, which could be distilled from plant waste and did not present the same risks as those posed from lead. Leaded gasoline was a fact of life for half a century, and its effects continue to be felt.