And there's claim that lead is maybe overrated after all https://www.cremieux.xyz/p/who-gets-exposed-to-lead
> With all said and done, it is abundantly clear that the effect of lead on IQ is overestimated and studies claiming that there’s no lower-bound for negative effects have not been adequately testing their hypothesis. Instead of effects of lead, what they've really been testing has largely been stratification of lead exposures by various causes of variation in IQ.