A couple recent stories about air pollution…

This one, which affects me personally because I live on the east coast, and illustrates the far-reaching effects of point-source pollution:
Western Wildfires Are Making Easterners Sick: U.S. Study, US News, 7 October 2021

What’s inside that smoke is part of the problem. Besides toxic gases, smoke contains tiny particles called PM2.5 that enter the lungs and contribute to multiple health problems. The study also looked at 18 hazardous air pollutants (HAPs) present in smoke, such as formaldehyde and benzene.

And this one which underscores the global problem of pollution:

The authors of a study published in PLOS Medicine* estimated that exposure to PM2.5 — pollutant particles with widths 30 times smaller than a human hair — was linked to almost 6 million premature births and 3 million underweight babies across the world in 2019.

* Ambient and household PM2.5 pollution and adverse perinatal outcomes: A meta-regression and analysis of attributable global burden for 204 countries and territories, PLoS Medicine, 28 September 2021

Both of those mentioned particles with a diameter less than 2.5 micrometers (PM2.5). Here’s a good map for assessing PM2.5 at any time of the day, anywhere in the world:
windy.com
Click “Air Quality” on the right side bar and pick PM2.5

This is PM2.5 across the US this morning, 8:00 am. eastern time: