A scientist at the University of Connecticut stumbled on a surprising finding when studying the effect of indoor air filters on people exposed to particulate matter — like from vehicle exhaust and hot cooking oil.
“I assumed we would see benefits on inflammatory markers in the blood system for a large percentage of people, maybe most or almost all of them,” said Douglas Brugge, professor and chair of the Department of Public Health Sciences at the University of Connecticut School of Medicine.
On average, Brugge and his team found no impact in levels of certain inflammatory proteins IL-1β and IL-6.
The study, in collaboration with the Tufts University School of Medicine, published in the American Journal of Preventive Cardiology, was conducted among people living within 200 meters of Interstate 93 in Massachusetts, just north of Boston. This demographic’s exposure to ultrafine particulate matter is much higher than average in the U.S.
Brugge instead found that inflammatory levels dropped in just a small subset of people who had a lot of belly fat — “abdominal fat, at an excess amount,” he said.
“There was a benefit on blood pressure, but only for people who had elevated blood pressure, and there was also a benefit on cognitive function, but only for people who were age 40 and older,” he said. “So the bottom line message that's emerging, in my opinion, is that there are vulnerable subgroups that benefit much more from these air purifiers than more generally young, healthy populations.”
Among this group, High-Efficiency Particulate Air filters reduced concentrations of the protein by nearly a quarter, significant because airborne pollution is linked with diabetes, fatty liver and heart disease.
The other unexpected finding was that people who had elevated Body Mass Index showed no benefit in inflammatory levels from HEPA filters.
“It was only people who had excess belly fat [visceral fat] that had a benefit from the air purifiers,” Brugge said.
Obesity medicine specialists like Dr. Wajahat Mehal, director of the Yale Weight Loss Program and professor of medicine at the Yale School of Medicine, have long known that higher fat around the abdomen is associated with higher inflammation.
“The two are very closely associated,” he said. “But it was not clear whether the inflammation that occurs in these people is entirely intrinsic or whether there are external factors, and this clearly seems to identify an external factor, which is very important because obviously you could potentially remove the external factor as opposed to an intrinsic process. So it clearly opens the door for some types of intervention.”
But the team could have, at the outset, compared people with truncal or visceral fat with those that did not have it, Mehal said.
“It's much more rigorous to have the idea ahead of time rather than find an association after the study has been completed,” he said.
Dr. Devika Umashanker, who practices bariatric medicine at the Hartford HealthCare Comprehensive Weight Management Program, also weighed in on the findings, urging further research.
“This is an interesting study. However, IL-1β is one of several pro-inflammatory cytokines associated with metabolic disease and a higher waist circumference,” she said. “Although this association is important to recognize, further research is needed to better understand the relationship between HEPA filtration and the health risks associated with greater waist circumference.”
Commercial air purifiers can be expensive — over $500. Another study is underway to find out whether a cheaper, homemade air filter for around $65 works just as well. Brugge, under a collaboration with Tufts, is beginning a clinical trial in Hartford and Boston.
