I’m always a little shocked when I hear otherwise very intelligent people make these sorts of statements about second hand smoke.
The second hand smoke you’d encounter on a sidewalk is completely harmless. Any affect, if any, to your health would be completely insignificant and unmeasurable.
Second hand smoke is harmful when exposed to heavy amounts of it in confined spaces for prolonged periods of time. Think decades not seconds.
In fact that was the original justification for indoor bans. It was in defence of staff who may encounter health issues after being exposed to indoor second hand smoke for 8 hours a day over decades. (Think single mom working at a bar) They weren’t put in place to preserve the health of customers, since any affect would be extremely minimal and voluntary.
I should try to dig this up some time but I recall reading once about one of the lead promoters of the first indoor smoking bans in NYC. He later had to step down out of principal, when things pivoted to outdoor bans. In his mind it would be completely irrational and unscientific.
Air pollution is definitely a significant problem but cigarette smoke is nothing more than a rounding error in the grand scheme of things. Look in to brake pad dust.