Finally a serious reply. Yep all that makes sense Wibbs.If there have been changes in fog frequency, rather than more public hysteria like the drone panic recently, then it wouldn't be surprising given weather is affected by global warming. The chemical smell is probably far from universal and possible explanations would be burnt ozone or pollution trapped underneath a temperature inversion or indeed fog caused by moisture being caught under a temperature inversion. Pollution or smoke (or just fog) could of course trigger allergies or similar things like asthma, and then people who get allergies in general could also be confusing correlation with causation. All whipped up into something it isn't by social and other media.
In Australia we quite often get smoke from bush fires or controlled burns getting trapped under temperature inversions, with the resultant garbage air quality until the inversion goes away.
What some people are also asking about is the texture. It’s got a snow like texture but isn’t snow. That is why some paranoid people are talking about ‘smart dust’ being trialled or a chemical of some sort. People pointing to the fact that government have done this before in the US over 200 times in one case.
https://en.m.wikipedia.org/wiki/Operation_Sea-Spray