Researchers who fitted study subjects with "air-pollution vests" to
continuously monitor exposure to both indoor and outdoor air
pollutants say that people are probably exposed to much higher levels
of pollutants than community monitoring stations typically indicate
and that this exposure affects both endothelial function and systolic
blood pressure.

Dr Robert Brook (University of Michigan, Ann Arbor) and colleagues
presented a poster with the results of their Detroit Exposure and
Aerosol Research Study (DEARS) during the American Heart Association
(AHA) 2008 Scientific Sessions. In an interview with heartwire, study
coauthor Robert Bard said that the results should serve as a reminder
to cardiologists, who tend to forget the extent to which air
pollution can harm the heart.

"Cardiologists are really not aware of this as a risk factor," Bard
said, despite a 2004 AHA scientific statement warning about the
cardiovascular risks of air pollution. What's needed, Bard said,
is "a greater awareness that air pollution is contributing to CVD."

Something in the Air

Brook, Bard, and colleagues enlisted 65 people--most of them women--
between the ages of 19 and 80 living in three areas of Detroit. All
subjects wore pollution-monitoring vests for 24 hours over five
consecutive days in the summer and five consecutive days in the
winter, only taking the vests off to shower or sleep, in which case
they were instructed to keep the vests close to them, in the same
room. As a result, Bard explained, the vests picked up not only
communitywide pollutants but exposures in the home, as well as short-
term exposures, when subjects walked past someone smoking or a bus
pulling away from a curb and emitting a burst of exhaust.

Investigators found that mean personal exposure to fine particulate
matter <2.5 µm (PM2.5), combining both indoor and outdoor exposures,
was 21.9 µg/m3 but ranged up to 225.4 µg/m3--much higher than that
being measured at community monitoring stations, which was a mean of
15.4 µg/m3 and a maximum of 41 µg/m3. Strikingly, a 10-µg/m3 increase
in personal exposure in the study was associated with brachial blood
vessel diameter narrowing within two days of the exposure and
increased systolic blood pressure (by 1.6 mm Hg) after one day of
exposure.

According to Bard, the main types of air pollutants detected by the
vests were "by-products of combustion," namely motor-vehicle exhaust
and second-hand cigarette smoke, despite the fact that all study
participants were nonsmokers living in nonsmoking households. Smoking
is still permitted, for example, in restaurants in Michigan, Bard
noted.

"Air pollution is actually noted as the 13th leading cause of death
worldwide," Bard reminded heartwire. "We already knew that air
pollution is associated with adverse cardiovascular events, including
increases in blood pressure, but the novel aspect here is that we
were measuring pollution that people were directly exposed to and
evaluating cardiovascular function. We found that the average person
in our study had increased blood pressure and reduced endothelial
function from the air they were exposed to in the previous 24 hours.
And importantly, these results were shown despite levels of ambient
air pollution that were at or below those recommended in the current
EPA guidelines."

He continued: "Patients shouldn't panic, because these levels are
still relatively low. But people need to be more aware of air
pollution as a CVD contributor and to support clean-air initiatives.
And if you have cardiovascular disease, you may need to try to avoid
exposure to air pollution at peak times."