“One of the new White House appointees to a critical environmental panel once said that the air these days is just too clean to promote good health. Robert Phalen, an air pollution researcher at the Irvine campus of the University of California, said in 2012 that children need to breathe irritants so that their bodies learn how to ward them off. “Modern air,” he told the American Association for the Advancement of Science, “is a little too clean for optimum health.””

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