When the sky becomes orange and hazy from wildfire smoke, modern humans are at greater risk than our earlier ancestors would have been.

This is because mutations that occurred tens of thousands of years ago made humans exquisitely sensitive to some types of air pollution.

Wildfire smoke includes two dangerous components: volatile chemicals, which include the things you can smell, and small particles, which you can’t. Both these components cause a lot of inflammation when we breathe them in and can trigger asthma attacks, and exacerbate chronic obstructive pulmonary disease (COPD) and heart attacks.

We don’t have any immune defences to stop the volatile chemicals, but we do have a few layers of protection from the small particles.

Some of these particles get trapped in the mucus that lines our nose, mouth and lungs and are cleared out as the mucus moves up and out of our lungs and is swallowed. (Count how many times you swallow while you read this article — you probably do it so automatically you aren’t aware of just how often you are helping clear the gunk out of your lungs).

Macrophages and the scourge of tuberculosis

Particles that aren’t cleared out by the mucus are........

© The Conversation