Marshall at Ban the Ban points out this little fact.
Asthma incidence in under 15-year-olds has increased from 5.8 per 10,000 in 1970 to 35.8 per 10,000 in 1997. (These are hospital discharge figures, not initial diagnoses.) During the same period, smoking rates dropped from 40% to 24% and according to the CDC, exposure of children to ETS decreased 75%. (The National Asthma Campaign, American Academy of Allergy, Asthma and Immunology, Jim Pirkle MD, PhD, CDC’s Environmental Laboratory)