Living very close to busy highways is known to generate poor air quality. I recommend anyone in those locations buy an air purifier for their kids' rooms.

I bought a couple reasonably priced HEPA purifiers and I change the filters on schedule. Replacement HEPA filters are very cheap.

Also watch out for things that we do indoors that can generate bad air quality. I had a friend who bought a VOC meter and noticed very high readings in his kid's room. He traced the source to his chemical and paint cabinet nearby, which he never considered because he couldn't smell anything. Throwing out a lot of the old containers dropped the measurements to the unmeasurable range.

NO2 is a very hazardous air pollutant which doesn’t get a ton of attention. The main sources are combustion engines and gas stoves. Asthma looks to be mostly caused by gas stoves.

I’ve got a sensor that can detect no2 and it noticeably spikes when using gas. Switched to induction after that.

Doctors used to prescribe a "change of air" in the 18-19th centuries. Maybe they still should.

I don't understand why we keep on building right next to highways which are some of the worst things for our health. You don't need to live in the countryside for that. Just stay roughly 1km away from them and the situation is significantly better.

There is evidence of a lot of ugly diseases caused by this, without even mentioning the constant 40+ dB background noise.

A friend of mine does research on air pollution from cars - the TL;DR is you should not live within a third of a mile of a highway. The falloff is pretty sharp, but you don't want to be in that zone.

My anecdote would be the revesre.

Living in the country gave me bad hay fever/asthma in the city much less asthma.

As long as the country doesn’t involve large scale farms because the glyphosate sprayed on them causes serious issues.