Since learning about air pollution, it turns out that the main problem (at least in temperate developed regions) is PM2.5 or PM0.1 particles in urban areas.

Things like CO, NOx, SO, O3 etc are at very low levels. The major problem is tiny particles <2.5um across (and especially those <0.1um across) coming mostly from diesel engines. They are small enough to be inhaled and go into the blood stream, and into the bodily organs. They are made of many different chemicals, so they have many different effects on the body, both physical and psychological. Research is ongoing.

The effects on pollinating insects, wild animals, crops and wild plants, I think it’s all still unknown. But it has been shown to affect bacterial growth and urban bacterial ecology.

This is fantastic.

It means that the problems of society - the depression and mental health crises, the mysterious rise in autoimmune diseases and food allergies, the obessity crisis, the birth rate crisis. They have no explanation but they are new and sudden. Maybe they all have a common cause - PM2.5 particles. It means that all we have to do is reduce the particle concentration from the air, and all these problems could disappear. Society could recover from the last 50ish years of madness.