1. Make up some scientific "evidence" that exposure to some common, harmless substance is actually harmful.
2. People believe it. Smart people make an effort to avoid it. Dumb people don't care.
3. Measure it 30 years later, and now there's a correlation between higher IQ and lower exposure to the substance. Higher IQ causes lower exposure to the substance.
I'm not saying this is the case with Pb, it's just a funny idea.
There are longitudinal studies that track people from childhood before the dangers of lead were widely known. There are also comparative studies where populations are studied with respect to occupational exposure.
Made me think of this:
1. Make up some scientific "evidence" that exposure to some common, harmless substance is actually harmful.
2. People believe it. Smart people make an effort to avoid it. Dumb people don't care.
3. Measure it 30 years later, and now there's a correlation between higher IQ and lower exposure to the substance. Higher IQ causes lower exposure to the substance.
I'm not saying this is the case with Pb, it's just a funny idea.