Leaded gasoline has a really crazy story. People have known that lead is highly toxic since the mid 1800s, and when tetraethyl lead was invented by Thomas midgley Jr in the 1910s, pretty much everybody at GM knew how toxic it was. Dozens of workers died from exposure, and Thomas himself was sick with lead poisoning when it was unveiled to the public. GM even went as far as naming it “ethyl” to avoid public backlash.
The reason it wasn’t banned until the 90s was because health officials in the 20s thought that exposure to drivers was so low that it wouldn’t reach toxic levels until decades down the line. Like, the 1970s. This wasn’t reviewed until the mid 70s and by that point the consequences were disastrous.There were some studies between the 20s and 70s, but most didn’t gain much traction. Many adults and children had increased levels of lead in their blood and lead has contaminated the groundwater and polluted the air. For instance, there is NO safe level of lead in blood, and Herbert needleman in the early 70s found some American schoolchildren had as much as 14 micrograms per deciliter This is the reason it wasn’t banned until the 90s in most countries. One could say we’re still recovering from that in some ways.
And the worst part? They could have used ethanol, an organic substance that’s a major additive in alcoholic beverages. It also prevents engine knocking and is highly flammable, but otherwise not even close to as toxic as TEL was. You still woudlnt want to breathe it in, but it probably wouldn’t have polluted our air and ground so much. GM refused to use ethanol though because it couldn’t be patented (being naturally produced?) and it wouldn’t be very profitable to use it to prevent knocking. TEL was far more profitable.