Tires! THE TIRES.

[Lynn]

This may be one of the dumbest statements in history:

"Anecdotally, although London is not a Victorian industrial smog city anymore, if you blow your nose here there's a hefty chance the snot comes out black; nitrous oxide doesn't have a color and there aren't many open hearths here so that points horribly to tire particulates in the air you breathe."

Without ANY OTHER process of elimination it "points horrbly to tire particulates.....???"

At least the writer used the term "anecdotally"; so he isn't representing it as hard science.

But still, in such a crowded City, how did the writer come to the conclusion that there are no other causes of pollution?