Scientist Claire Patterson spent over 20 years trying to convince the public that lead was poison.
The inventor of leaded gasoline meanwhile once went to New Jersey to argue that leaded gasoline was perfectly safe, by pouring tetraethyllead onto his hands, and then putting a bottle of it under his nose and inhaling it for 60 seconds saying he could do it every day without any problems. He then had to leave work after being diagnosed with lead poisoning.
He also went on to invent Freon, a CFC that was later banned after being shown to be responsible for ozone depletion.
Then he got polio, so he invented another thing, a pulley system that let him pull himself out of bed. He would then die after becoming entangled in this and strangling himself.