https://ourworldindata.org/intelligence
https://ourworldindata.org/air-pollution
We have decades of data to show this positive correlation. Now I'm wondering how the study measured intelligence and of course who funded this study.
Edit: Seems like a lot of people are misunderstanding my point. I'm not saying air pollution is good. I think air pollution is bad. I'm just pointing out raw objective data which contradicts the study.