Is there a link between air conditioning and asthma? This report in the April 2009 issue of Environmental Health Perspectives suggests there might be. Over a thirty year period, the number of homes with air conditioning went from 15 percent in 1972 to over 60 percent in 2002. Over the same period the nation has witnessed a doubling of the number of asthma cases, from 3.4 percent to 7.8 percent. The authors concede they cannot tell if air conditioning directly causes asthma or if other factors, such as the more indoor-based, sedentary lifestyle that may go along with it, are to blame. But they do assert that reduced fresh air infiltration and increased exposure to airborne particulate matter (dust, etc.) may negatively impact indoor air quality. For tips on how to counteract this, read our article "Is Your Home's Air Safe" and this one on cleaning air ducts.