It is not been proven that second-hand smoke causes miscarriage, although, there’s a an increase of risk. Definitely not the cause of thousands and thousands of deaths.
And even the studies that have been performed, it was done in households in which the pregnant woman was constantly exposed to secondhand smoke. Occasional second hand smoke has no known side effects.
In terms of triggering asthma attacks, many, many environmental factors trigger asthma attacks. Yes, secondhand smoke is on the list as well. As is exercise, changes in weather, pollination, some medications, perfume, deodorant, paint, nights, fog, excitement, stress, anger, Etc. Of the hundreds of triggers, second hand smoke is one of them. Banning something because of it is nonsense.