A two-decade study that looked at 2,000 kids in 5 cities in Southern California was recently published in the New England Journal of Medicine. Its results remind us once again of the importance of clean air. After all, air is now the world’s biggest environmental health risk with 7 million deaths per year. The researchers found the relationship between the decline of air pollution in the region since the early 1990s and the “statistically and clinically significant improvements” in children’s lung function and growth. In fact, the number of school-age kids with “abnormally low lung faction” dropped by more than half between the 1994-1998 group (7.9% with abnormally low lung function) and the most recent…