Adults aged 40 and older completed a test of mental flexibility about 12 percent faster after using a HEPA air purifier at home for one month than they did after a month using a fake purifier, according to a randomized crossover trial published in Scientific Reports in April.
The study was conducted in Somerville, Massachusetts, a densely built city just outside Boston that sits along Interstate 93 and Route 28. That location was chosen deliberately, because traffic related air pollution there runs high, making it a useful setting for testing whether filtering indoor air produces measurable effects.
