The water crisis in Flint, Michigan, has brought the health effects of lead back into the public eye, and in a big way.
In that context, it's worth noting that lead was still a part of everyday gasoline more recently than many drivers remember.
Leaded gasoline was sold in the U.S. until January 1996.
While the environmental issues surrounding leaded fuel were well known by that time, it was kept available for pre-1975 cars that required lead to lubricate their valves.
Lead was developed into an additive for gasoline in 1920s to help engines run better.
It is poisonous to humans, leading to severe effects including neurological damage--something that has been known ever since lead was first mined.
Nonetheless, leaded gasoline became the standard in the U.S. and around the world for decades to come.
The tremendous public-health consequences of releasing so much lead into the atmosphere through exhaust emissions became apparent largely through the work of geochemist Clair Patterson in the 1960s.
While attempting to determine the age of the Earth by precisely measuring the amounts of lead in rock samples, Patterson became aware that there were large amounts of material in the environment.
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He subsequently measured lead levels in the ocean, and in ice cores taken from the Arctic, and found that higher levels of lead corresponded to the time period when leaded gasoline was in use.
This created a public outcry against lead in consumer products--but may not have been the ultimate cause of leaded gasoline's demise.
Perhaps just was important to regulators was the fact that leaded gasoline fouled the new catalytic converters that were the only way to meet new emissions standards mandated for 1975-model-year cars.
In 1973, the U.S. Environmental Protection Agency (EPA) unveiled a plan to gradually phase out leaded gasoline, beginning in 1976.
To account for the fact that cars built before the new regulations were enacted would stay on the road for some time, that process took 20 years.
Virtually every motor vehicle built in the world today now uses a catalytic converter of some sort to reduce tailpipe emissions of carbon monoxide, nitrogen oxides, and hydrocarbons.
There has even been some speculation that lead reduction helped contribute to the significant drop in crime during the 1990s.
A 2013 study argued that lower levels of lead reduced instances of learning disabilities in children, although there likely other factors behind the crime drop.
But there is no doubt that the end of leaded gasoline was a major victory for public health.
[hat tip: Brian Henderson]