Leaded gas was never fine. GM avoided using the word lead about their tetraethyllead product because everyone knew lead was problematic. Lies and lobbying assured that they knowingly could go ahead and poison the whole world.

Wikipedia has a history of how lead was known to cause problems, dating back to antiquity. Some excerpts:

> Dioscorides, a Greek physician who lived in the 1st century AD, wrote that lead makes the mind "give way".[121][274]

> Lead poisoning from rum was also noted in Boston.[291] Benjamin Franklin suspected lead to be a risk in 1786

> The first legislation in the UK to limit pottery workers' exposure to lead was included in the Factories Act Extension Act in 1864, with further introduced in 1899. William James Furnival (1853–1928), research ceramist of City & Guilds London Institute, appeared before Parliament in 1901 and presented a decade's evidence to convince the nation's leaders to remove lead completely from the British ceramic industry.

I don't know much about forever chemicals. Is there the same level of evidence as we had for lead?

It was pretty obvious from the get-go that leaded gas was an absolutely horrible idea, but this was before the mass-media age, so people didn't know that people who worked at the tetraethyl lead plant were going mad so often that it became known as the "looney gas building".[0]

Doses make the poisons, and apparently the dose for some of these chemicals is much, much higher than tetraethyl lead.

Also, apparently the molecular diagram for TEL sorta looks like a hackenkreuz. How appropriate.

[0]https://www.wired.com/2013/01/looney-gas-and-lead-poisoning-...