Firstly, you're facts are wrong. If you check the actual numbers for the 1920s, the average life span
(not life expectation) for most odf the modern world was most likely around mid-'50s to age 59 (in USA); other industrialized countries it was around 50 yrs to low-50s.
Secondly, what an odd conclusion that you propose... that breathing coal smoke has anything to do with increasing life expectancy. I've seen not one single reliable resource that makes such a claim. Can you provide a single one that states such a conclusion?
The reason life expectancy increased was due to an improvement in quality of life and economics for the average person, along with less general pollution/better urban sanitation, better nutrition, and better medication and medical expertise.