How safe is the air to breathe? 50M people in the US don't know

Study:

Identifying air quality monitoring deserts in the United States - https://www.pnas.org/doi/10.1073/pnas.2425310122 | https://doi.org/10.1073/pnas.2425310122

Having lived in the suburbs most of my life, I always considered air quality to be an important societal issue but not something to worry about as an individual.

Then I went on vacation to the carribean. At home I sometimes get out of breath climing a few flights of stairs.. but down in Puerto Rico I was able to go snorkeling and even hike up a mountain without any problems.