The University of Southern California Children’s Health Study measured lung development in thousands of adolescent children in communities across the Los Angeles area since 1993. The project found large gains for the children studied from 2007 to 2011, compared to children of the same age in the same communities from 1994-98 and 1997-2001. the study provides strong evidence that improved air quality by itself brings health benefits.
the combined exposure of nitrogen dioxide (NO2) and particulate matter of diameter under 2.5 microns (PM2.5) fell approximately 40 percent over the course of the study. As pollutants dropped, lung growth improved more than 10 percent, according to the long-term data. The percentage of children in the study with abnormally low lung function at age 15 dropped from nearly eight percent for the 1994-98 cohort to 6.3 percent in 1997-2001 and to just 3.6 percent for children followed between 2007 and 2011.
— source thinkprogress.org