It is hard to think of breathing as a luxury—but for my granddaughter that is her constant reality. Our family lives in Charlotte, North Carolina, which is one of the smoggiest cities in the country, largely because it’s surrounded by a ring of five coal-fired plants. In the five generations that my family has lived here, never has there been an issue more serious than the air we breathe. Terms like “bad air days,” “extreme weather,” or “climate change” may feel vague or far away to some. But behind these words are people that are like my granddaughter and me. I came across a study [ 2010...