Cardiovascular Benefits of Air Filters in a Polluted Environment

Scientists are concerned about the effects of air pollution on the development of cardiovascular disease. Thus it is known that minute particles in the air we breathe are associated with cardiovascular mortality. Canadian researchers investigated the problem in a small town where the use of wood burning stoves was considerable by observing the effects of portable air filters on two markers for the likely development of atherosclerosis. Their findings are published in the American Journal of Respiratory and Critical Care Medicine.

45 healthy adults from 25 homes in a small town in British Columbia in this crossover study.  Each household was given two HEPA filters, one for the main activity room and one for the bedroom. The participants were randomized to consecutive 7-day periods in which the filters were either active or not active. The researchers measured reactive hyperemia; this is a temporary increase in blood flow or redness of the skin which follows a period of ischemia, or blood flow shortage. Reduced reactive hyperemia indicates that blood vessels have an impaired response to changes in blood flow, and is a marker of the earliest changes of atherosclerosis, affecting the endothelium or inner cell lining of the arteries. Blood levels of C-reactive protein (CRP), which increase during inflammation, were also measured.

About two-thirds of the indoor concentration of particulate matter was generated indoors, with the rest leaking in from outside. Reactive hyperemia improved by an average of 10% when the filters were turned on compared with when they were turned off. At the same time, there was an average drop of 33% in CRP concentrations.

While there is no evidence that these fairly modest changes would have measureable beneficial effects upon cardiovascular function, they clearly indicate potential reversal of impaired endothelial cell function and systemic inflammation, both predictors of cardiovascular disease. They provide further support for the necessity to improve air quality in places where it is poor, either from industrial or residential pollution. The findings of this study provide a link in the chain of evidence showing detrimental effects of air pollution.