Air pollution is not due to climate change, unless you count CO₂ as air pollution, but that's eargrayish misreasoning — that's not the kind of air pollution that causes 10% of all deaths. The sort of local air pollution we're talking about amounts to factories strip-mining local children's lungs for profit; it's a form of fighting each other.
Rainwater harvesting risks seem to be primarily due to birds pooping on your roof and other fecal contamination, and they can be adequately mitigated by boiling or chemical sterilization: https://www.nature.com/articles/s41545-019-0030-5.
Climate change very likely would collapse your civilization, given enough time, but that isn't what is happening now.
10% of all deaths each year are due to air pollution. There's pretty much no place on earth where unfiltered rainwater is still safe to drink. Ocean acidification is accelerating and killing off the organisms that are both the biggest producers of oxygen and the biggest sequesterers of carbon.