N. Mueller wasn’t sure whether the air purifiers in his living room and bedroom were real. That was the point. The Navy veteran had signed up to have them whir away in the background of his life, either filtering or just pretending to, while he submitted to regular blood draws, nostril scrapes, and breathing tests, to help figure out whether the working machines improved chronic obstructive pulmonary disease beyond the placebo effect.

Harvard researchers had spent five years and some $3.8 million from the National Institutes of Health trying to answer this question when Mueller heard that the study might never yield results. In May, amid a feud with the university, the Trump administration had abruptly terminated the grant that was funding it with one year and some $734,000 still to go. W

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