Study shows decrease in children's asthma from traffic-related air pollution

Children's asthma attributable to traffic-related air pollution dropped substantially from 2000 to 2010, a new study in the peer-reviewed journal Environment International concludes.

By the numbers ... Researchers found a 33% drop over the study period: "[W]e estimated on average 209,100 and 141,900 attributable cases due to NO2 in 2000 and 2010, respectively, which accounted for 27% and 18% of all childhood asthma incident cases."

What they did: The study combined a series of datasets to produce a granular nationwide analysis, focusing on the link between vehicle nitrogen dioxide (NO2) emissions and asthma.

The big picture: Co-author Haneen Khreis of Texas A&M University, writing in The Conversation, looks at what's behind the decline...

"There may be multiple causes, including more fuel-efficient vehicles, more stringent regulation on nitrogen oxide emissions and, potentially, reductions in total vehicle miles traveled due to the recession."

But, but, but: Despite the progress, Khreis notes that traffic is still making lots of kids sick, and that children in urban areas had twice the NO2-linked percentage of asthma compared to rural kids.

• She's hopeful that their mapping and analysis will help policymakers, transportation agencies, medical groups and others address the problem.

Go deeper: Wildfires cause more than breathing problems across California