[coffeecat]

"Correlation does not imply causation" is a simple idea, but it truly cannot be emphasized enough. Establishing a correlation certainly does help to strengthen an already-compelling causal mechanism theory. Pulling high doses of carcinogen-filled particles into your lungs causes lung cancer? Sounds about right. Reduced IQ from exposure to a neurotoxin at levels significantly lower than that which produces clinical symptoms? Maybe, but I'd say the burden of evidence is higher on that one.

> Finally, when you suggest there are confounders, that's a causal claim. What confounders do you have in mind here, what standard of evidence do you need to accept them as confounders, and do they supersede the evidence we have for lead and IQ?

Dirt and dust ingestion, for which lead is a noisy metric. It's no accident that the correlation between lead and IQ is strongest at age 2. That's the age by which the smarter children have figured out that dust bunnies don't taste very good.