"If you put
together the evidence, clearly day-to-day changes in particle concentration do
make a very small but significant difference in terms of increasing
susceptibility for cardiovascular events" such as heart attacks, said Dr.
Sanjay Rajagopalan, who studies pollution and cardiovascular health at The Ohio
State University in Columbus.
"This seems to be
particularly so for individuals with pre-existing heart disease,"
Rajagopalan, who wasn't involved in the new study, told Reuters Health.
Researchers led by Dr.
Hazrije Mustafic from the Paris
Cardiovascular Research
Center
Those reports included
anywhere from about 400 to more than 300,000 people, with heart attacks
confirmed in hospital records and disease and death registries.
The combined findings
showed that heart attacks were slightly more common at high levels of every
main pollutant except ozone, Mustafic's team reported in the Journal of the
American Medical Association.
The differences in
heart risks were small. For most of the pollutants, an increase in
concentration of 10 micrograms per cubic meter of air -- the typical standard
used to assess harm, and barely noticeable to a person breathing the air -- was
associated with a one to three percent increase in the chance of having a heart
attack in the next week.
"Even if the
relative risks are low compared with traditional risk factors such as smoking
status or hypertension or diabetes, in fact everybody is exposed to air
pollution in industrialized countries," Mustafic told Reuters Health -- so
even small effects can add up.
She said that when
people inhale polluted air, small particles can reach the tiny sacs in the
lungs and be carried in the bloodstream to the heart.
Pollutants may also
affect blood vessels' ability to expand and contract in order to keep blood
pressure constant.
Researchers have
blamed that effect for increasing evidence that high-pollution days are also
tied to a person's risk of suffering a stroke, including findings from a study
published Monday in the Archives of Internal Medicine. Another report in the
same journal linked long-term exposure to air pollution with faster cognitive
decline in older women (see Reuters Health story of February 13, 2012).
Mustafic said that air
pollutants are associated with harmful health effects even at levels that are
considered safe by the World Health Organization and other monitoring groups.
That might mean it's time to lower some of the maximum allowable levels, she
said.
"Clearly, air
pollution at least in North America and Europe
has remarkably improved in the last few decades," Rajagopalan added. But,
"the epidemiology continues to support an association with even (current)
levels and an increased risk of cardiovascular disease."
He said that people
who should be concerned are those who already have heart disease, and possibly
those who are at higher risk of a heart attack because of diabetes or obesity.
"If you're really at risk,
it might be reasonable to avoid areas of high pollution (and) avoid commuting
during those times or spending time in rush-hour traffic," Rajagopalan
said. "Minimize exposure as much as you can."
