Clean up the smog, reduce kids' asthma cases. It might seem like a logical one-two, but now researchers at USC have put some hard data behind it, reports NPR. In the study published in JAMA, the scientists looked at how asthma rates have changed as air quality has improved in Southern California. Generally speaking, pollutants in the air—nitrogen dioxide as well as fine particles—dropped by 20% over a 20-year period beginning in 1993. "This corresponded with about a 20% decline in the rate of new asthma cases in children," says postdoctoral fellow Erika Garcia. "It's fairly substantial." The study took advantage of the Southern California Children's Health Study, which has tracked the health of thousands of children over the years, per Popular Science.
The advantage of that is researchers could compare asthma rates of kids who grew up in the 1990s with those who grew up in the same area a decade later. The results were consistent: As the air improved, asthma cases dropped. The study lends evidence to advocates who say the cost of pollution control is worth it, says a physician on the state's Air Resources Board. "There's been a concerted effort in California over the period of this study to reduce motor vehicle emissions in general and diesel emissions in particular," says John Balmes. "And I think this study shows that it's paying off." Both stories note that the study comes amid growing skepticism at the federal level of a link between air pollution and public health. (In Britain, a young girl's death is being blamed on air pollution in a first-of-its-kind case.)