They may not have had the imagination to envision the scale of the resulting problem; but the producers of organolead anti-knock compounds had no reason to be cheerful about its safety. The good Mr. Midgley had a number of workers die during his R&D, and got a pretty stiff hit of lead poisoning himself.
Freon, he arguably has clean hands on, since he died decades before its ozone depleting effects became known. Lead? He just didn't give a fuck, apparently.