[hedora]

I assume the study authors controlled for such things. For example, they could bin the study participants by socioeconomic group, race, location, etc, etc, etc, and then show the average IQ loss per bin.

I haven't read the study, but statisticians do this stuff for a living, and there are definitely ways to control for sample biases that let you distinguish between "poorer people have lower IQs and are exposed to more lead, and the root cause of both is being poor", and "lead leads to lower IQs within all socioeconomic groups we could think of and measure"

[cltby]

But these controls could be done for any IQ-related study. Is IQ-skepticism based on the belief that IQ researchers generally don't use controls? That lead-IQ researchers alone do this?

[astrange]

You can't demonstrate causation by controlling for things, because of collider bias.

https://en.wikipedia.org/wiki/Bad_control

You need better methods like an intervention study or a natural experiment to show causation.