Exposure to fine particulate matter in the home can lead to blood vessel inflammation that leads to heart
disease. In a study, Canadian scientists learned HEPA filters can reduce concentrations of fine particulates
inside homes by 60% and woodsmoke by 75%.

The findings, published in the American Thoracic Society's American Journal of Respiratory and Critical
Care Medicine, specifically looked at the effect of air filters for reducing the amount of exposure to pollution
from wood stoves in a small community in British Columbia where wood burning stoves are the main
sources of pollution.
The researchers recruited 45 adults from 25 homes whose homes were monitored for two consecutive 7-
day periods. During the first week a HEPA filter (Honeywell model 50300) was used in the main part of the
household, and in the bedroom, a HEPA filter (Honeywell 18150) was used. In the first part the filters were
used normally and for the second week the filters were removed.
Excluded from the study were households who reported tobacco smoking. During the monitoring period, the
participants were unaware whether the air was being filtered.
"Our main objectives were to evaluate the potential for a simple intervention to improve indoor air quality and
reduce pollution-related cardiovascular health risks and to better understand the mechanisms that contribute
to air pollution-related cardiovascular health problems" said Ryan Allen, PhD, assistant professor, Simon
Fraser University, Burnaby, British Columbia.
"Specifically, we were interested in learning more about the effects of residential wood smoke on the
endothelium, the cells that line the inside of blood vessels, and on systemic inflammation, which is related to
cardiovascular disease risk."

The researchers measured C-reactive protein, an inflammatory protein marker to find the benefits of HEPA
filters for lowering the chances of cardiovascular disease inside the home.
The study authors also looked at reactive hyperemia that measures periods of decreased blood to the
tissues. They found HEPA filters resulted in a 9.4% increase in reactive hyperemia index and 32.6%
decrease in C-reactive protein.

The authors concluded, "Air filtration was associated with improved endothelial function and decreased
concentrations of inflammatory biomarkers, but not markers of oxidative stress. Our results support the
hypothesis that systemic inflammation and impaired endothelial function, both predictors of cardiovascular
morbidity, can be favorably influenced by reducing indoor particle concentrations."
The authors note past studies showing the benefits of high efficiency particle air filters can reduce
pollution in urban areas from vehicle emissions, but few have addressed the impact on wood smoke that is
increasingly being used as a heat source.
The new study shows HEPA filters can improve blood vessel health and curb heart disease for residential
owners who use wood burning stoves, in addition to reducing other fine particulate matter in the home that
can contribute to chronic disease.

Am. J. Respir. Crit. Care Med. 2011, doi:10.1164/rccm.201010-1572OC
"An Air Filter Intervention Study of Endothelial Function Among Healthy Adults in a Woodsmoke-Impacted
Community"