In this photo taken April 4, 2017, Javier Sua, 11, demonstrates how he uses an inhaler at his home in Fresno, Calif. He uses it to combat asthma, made worse by air pollution in the San Joaquin Valley. On some days, his mother keeps him inside, when he would rather be rough-housing on the backyard trampoline, but the risks are too high. Hundreds of people each year in the San Joaquin Valley die premature deaths from poor air quality. (AP Photo/Scott Smith)
Read more »In this photo taken April 4, 2017, Javier Sua, 11, demonstrates how he uses an inhaler at his home in Fresno, Calif. He uses it to combat asthma, made worse by air pollution in the San Joaquin Valley. On some days, his mother keeps him inside, when he would rather be rough-housing on the backyard trampoline, but the risks are too high. Hundreds of people each year in the San Joaquin Valley die premature deaths from poor air quality. (AP Photo/Scott Smith)