That's one hard to parse sentence there... or maybe I've been exposed to too much lead as a child :)

In all seriousness, IQ is an important component of intelligence, mainly "fluid intelligence" that correlates well to learning speed in science and technology field, so for anyone that needs to do lots of learning/unlearning and career/domain hopping like we're all going to do more and more in the future it matters a hell of a lot!

I a world where someone could pick a job/domain and stick to it for life, IQ would matter but less... but it's not the world we're living in, everything is accelerating and our kids are likely to go through quite a few career changes / professional re-conversions etc.

Seems a reasonable assumption that lowering IQ is a decent proxy for other damage lead does to the brain, right? It would be weird if it just damaged the bits associated with doing well on IQ tests, and left the rest alone.

E.g. it happens that IQ is something we measure, and EQ much less so. That lead leads to measurable reductions in IQ is strong evidence that it damages EQ too. (As its association with crime would suggest.)

Adding this to the list of things IQ tests accurately predict:

1) school performance

2) job performance

3) income

4) crime rate

5) health and mortality

6) quantity of lead exposed to

7) NOT intelligence

>3) income

Hm, I know some obvious contradictions. Just saying.. not interested in discussing this.

Individual cases do not invalidate statistical trends...

every rule has its exception(s)

Genuinely curious, Where are you learning this from?