MARY LOUISE KELLY, HOST:
Children who live in places with lots of air pollution are more likely to develop asthma. So if you clean up the air, does that protect kids' health? NPR science correspondent Richard Harris reports on a study that answers that question.
RICHARD HARRIS, BYLINE: Southern California is notorious for its poor air quality. But over the past two decades, the air has been getting better. That led Erika Garcia, a postdoc at the University of Southern California, to ask a simple question.
ERIKA GARCIA: We know that there's been reductions in air pollution. Let's see if, concurrently, there are improvements in health outcomes during that same time period.
HARRIS: As it happens, scientists have been checking in periodically on the health of students in 12 different communities in the Los Angeles area. Garcia and her colleagues tracked air quality trends in those regions during three different time periods, starting in 1993 and ending in 2014.
GARCIA: Some communities declined a little bit. Some communities declined a lot. Some communities didn't decline at all. How does that relate to the changes in asthma incidence rate in these three different sets of students?
HARRIS: They report now in the journal JAMA that overall, hazardous air pollutants, including nitrogen dioxide and fine particles, declined by about 20% over the time period.
GARCIA: This corresponded with about a 20% decline in the rate of new asthma cases in children.
HARRIS: That sounds fairly substantial - 20%.
GARCIA: Yes, it is fairly substantial.
HARRIS: John Balmes, an environmental health professor at UC San Francisco and the physician member of the California Air Resources Board, agrees. The study doesn't prove cause and effect, but it's not a big leap to find that cleaner air means less illness. And Balmes says it's important evidence in the ongoing debate over just how much money we should spend to improve the air.
JOHN BALMES: 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. And I think this study shows that it's paying off.
HARRIS: State policy aimed at both health and climate change calls for the gradual phasing out of gas and diesel vehicles in favor of electric cars, trucks and buses. Industry once resistant to these rules is now split with clean energy companies in favor of clean air regulations, Balmes says.
BALMES: That has allowed us to move forward, I think, perhaps, at a brisker pace than we might have otherwise.
HARRIS: It's a different story on the federal level, however. The Environmental Protection Agency in the Trump administration is skeptical of the link between clean air and health. George Thurston, a professor of environmental medicine at New York University, says the new study from Southern California comes at a key moment.
GEORGE THURSTON: Because it confirms what is being questioned by the present EPA, which is that - are there really health benefits to clean the air? We think that that should be obvious, but that's a question that they're asking.
HARRIS: He calls the study a landmark in demonstrating the benefits of cleaner air on asthma, which is the most common chronic disease in children.
Richard Harris, NPR News.
(SOUNDBITE OF CHRIS COHEN'S "TORREY PINE")
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.