Earlier quoted context omitted.
Article says > It's not clear precisely how pollution impacts cognitive decline, though Chen suggests that pollution may have a negative effect on the brain's white matter, which could vary between men and women. As NPR has reported, "the brain's white matter coordinates communication among brain regions." > James Hendrix, the director of Global Science Initiatives at the Alzheimer's Association, was skeptical of the…
Re the second quote, what about lead levels (in air or water pollution), I thought they'd been linked pretty effectively with cognition issues.
But there are many different ways cognition can be effected, white matter isn't the only brain matter. Also this study wasn't specifically about lead.