That is, in fact, what he's saying, although it wasn't definitively shown. But clearly it was known to be a carcinogen when they built my high school in the ea

That is, in fact, what he's saying, although it wasn't definitively shown. But clearly it was known to be a carcinogen when they built my high school in the early 70's, and yet they were still using it as a standard insulation and fireproofing material. I have lots of asbestos tape in my house, too. Lead paint, though - there's a good one. Everybody knew you shouldn't drink it, but nobody suspected the dust was a problem. (Although Japan had already banned it by the 20's, if I recall correctly, while America was still merrily painting everything in sight with toxins). And of course, the Romans didn't even know you shouldn't drink it. Although the benefits lead plumbing in Rome due to widespread availability of clean water almost certainly outweighed the costs of some stupider Romans.