Observational evidence is confounded by numerous variables, to say that “urban centers have clusters of asthma and rural centers don’t” ignores all of the extant factors of the urban environment. Studies have found that gas stoves could play a role in development of childhood asthma. It may not scale to the magnitude of that seen in urban cores, with the addition of other sources of air pollution, but it’s weird to discount the studies entirely as a propaganda campaign by Con Ed.