No, we knew lead was bad. We knew what heavy metal poisoning looked like, we knew lead caused heavy metal poisoning. We knew of a hell of a lot more concrete effects than average lower scores on IQ tests.

> The loss of IQ points happens to all kids living in cities

No, it didn't. The reduced test scores happened _on average_.

I won't rule out that what you said is correct, in that it may well be the fear that "my child may lose 1-5 IQ points!" helped get lead banned, but if so, that's an indictment of society.