Here's the point I'm trying to articulate: we used to blame nearly all the non-smoker lung cancer incidents on 2nd hand smoke. Smoking was everywhere. It was terrible. I hated it so much.

Now smoking has dropped significantly and smoking indoors and in many public spaces is banned. But the non-smoker lung cancer rates don't appear to be dropping accordingly.

Did we replace the 2nd hand smoke with some other cancer causing particulates? Or were we wrong about 2nd hand smoke and there was something else in our environment the whole time?