You may have never heard of him, but Thomas Midgley was considered one of the great chemists and inventors of his time. But perhaps no single person in history has done more harm to our earth.

While working at a subsidiary of General Motors in 1921 he developed tetra-ethyl lead, or TEL. This was an additive for gasoline to reduce the problem of ‘knocking’ in car engines.

In a few years, nearly every automobile on earth was pumping lead into the air. This lead, a known neurotoxin, ended up in our blood. After TEL’s introduction, nearly 90% of children in America had twice the level of lead in their blood that is considered safe. Even light exposure can cause a decrease in intelligence and an increase in antisocial behavior. Before lead was phased out in the last decades of the last century it caused perhaps millions of illnesses and deaths around the world.

But our story does not end here. In the late twenties, Midgley synthesized the first fluorocarbon, commonly known as CFCs. These are the same CFCs that left a big hole in our protective ozone layer. CFCs are now banned but the damage is unlikely to heal until well past our lifetimes.

Midgley’s inventions seemed brilliant at the time but we will be living with their consequences for a long time. Let’s hope we can learn a lesson from Midgley’s story.