You can try to bike behind a hybrid during a cold winter morning.

In the US, near a major roadway on a cold morning, the fumes are strong. Not every car or truck is maintained properly and running in cold weather really magnifies that effect.

You might have very good smog checks. Here in NZ I've recently replaced my Tesla's HEPA air filters which includes carbon filter which. I've got them slightly cheaper from somewhat ok supplier. Turns out there's ton of fake filters out there (i.e. vacuum filters).

I was suffering every day I was driving it. Smog is insane everywhere.