I don't understand the correlation between air quality and asthma. In the United States, asthma rates are way up. This article blames at least part of the increase on air pollution, specifically nitrogen dioxide. But nitrogen dioxide concentrations in the United States are down by 54% since 1990 alone. https://gispub.epa.gov/air/trendsreport/2021/#air_trends It isn't outdoor air pollution that's driving the increase in asthma because outdoor air quality is improving (and has been improving for over 50 years in the United States.

I would imagine that today's natural gas stoves are cleaner than in the past, natural gas appliance don't seem to be driving the increase in asthma either.

My point is that the data isn't clear what is driving the increase in asthma.