Women In Polluted Areas At Higher
Risk Of Cardiovascular Disease
05 Feb 2007.
Women living in areas with higher levels of
air pollution have a greater risk of developing
cardiovascular disease and subsequently dying
from cardiovascular causes, according to a
University of Washington study appearing in
the Feb. 1 issue of The New England Journal
of Medicine. The study is one of the largest
of its kind, involving more than 65,000 Women's
Health Initiative Observational Study participants,
age 50 to 79, living in 36 cities across the
United States.
UW researchers studied women who did not initially
have cardiovascular disease, following them
for up to nine years to see who went on to
have a heart attack, stroke, or coronary bypass
surgery, or died from cardiovascular causes.
They linked this health information with the
average outdoor air pollution levels near each
woman's home, and found that higher pollution
levels posed a significant hazard - much higher
than previously thought - for development of
cardiovascular disease.
The researchers studied levels of fine particulate
matter, which are tiny airborne particles of
soot or dust, and can come from a variety of
sources, like vehicle exhaust, coal-fired power
plants, industrial sources, and wood-burning
fireplaces. These particles are less than 2.5
microns in diameter -- about 30 to 40 of them
would equal the diameter of a human hair. Particulate
matter levels are monitored and regulated by
the U.S. Environmental Protection Agency (EPA).
They're typically invisible to the human eye
once they're in the atmosphere, though they
may be visible in dense clouds as they come
out of a tailpipe, smokestack or chimney, and
are responsible for urban haze.
"These soot particles, which are typically
created by fossil-fuel combustion in vehicles
and power plants, can contain a complex mix
of chemicals," explained Dr. Joel Kaufman,
professor of environmental & occupational
health sciences, epidemiology, and medicine
at the UW, and leader of the study. "The
tiny particles - and the pollutant gases that
travel along with them - cause harmful effects
once they are breathed in."
Fine particulate matter is measured in micrograms
(or millionths of a gram) per cubic meter;
cities in the study had average levels of fine
particulate matter ranging from about 4 to
nearly 20 micrograms per cubic meter. The researchers
found that each 10-unit increase in fine particulate
matter level was linked to a 76 percent increase
in the risk of death from cardiovascular disease,
after taking into account known risk factors
such as blood pressure, cholesterol, and smoking.
Higher long-term average levels of fine particulate
matter also led to a higher overall risk of
cardiovascular disease events, including stroke
and heart attack.
They also found that local differences in particulate
matter levels within a city, as well as exposure
differences between cities, translate to a
higher or lower risk of cardiovascular disease
and related death.
"Our findings show that both what city
a woman lived in, and where she lived in that
city, affected her exposure level and her disease
risk," said Kristin Miller, first
author of the study and a doctoral student
in epidemiology at the UW.
Previous studies have found apparent links
between airborne particulate matter and cardiovascular
disease, but this study was the first to look
specifically at new cases of cardiovascular
disease in previously healthy subjects and
local air pollution levels within metropolitan
areas. Researchers used data from the multi-site
Women's Health Initiative Observational Study,
which is funded by the National Heart Lung
and Blood Institute of the National Institutes
of Health (NIH), and coordinated through a
center based at the Fred Hutchinson Cancer
Research Center in Seattle. The EPA and the
National Institute of Environmental Health
Sciences provided funding for the study of
the effects of air pollution.
Scientists don't understand exactly how fine
particulate matter may be leading to cardiovascular
disease, but some believe that the soot particles
are accelerating atherosclerosis, or hardening
of the arteries, which is the major precursor
of heart disease.
"This could be a cellular and biochemical
process that starts in the lung and then proceeds
from there into the cardiovascular system," Kaufman
explained. "Or it could be that these
very small particles actually enter the blood
stream through vessels in the lung, and then
begin affecting blood vessels throughout the
body." Kaufman is leading a major new
EPA-funded study to uncover these mechanisms
- an air-pollution study based on the NIH's
Multi-Ethnic Study of Atherosclerosis, or MESA.
The MESA Air Pollution Study tackles two key
areas for understanding this problem, Kaufman
said: investigating the mechanisms through
which particulate matter leads to cardiovascular
disease, and identifying the sources of pollution
that cause the problem. "Preventing these
effects requires reducing the pollution at
the source," Kaufman said.
The implications of this connection could be
very significant.
"More than one out of three deaths in
the United States are due to cardiovascular
disease - it's the leading cause of death," Miller
said. "If the annual average concentration
of fine particulate air pollution can be reduced,
it would potentially translate on a national
scale to the prevention or delay of thousands
and thousands of heart attacks, strokes, and
bypass surgeries, not to mention fewer early
deaths."
###
An editorial from researchers at the Harvard
School of Public Health and Brigham and Women's
Hospital will accompany the study in the Feb.
1 issue of the journal. In that editorial,
the authors suggest public health interventions
to address this problem, as well as a tightening
of the EPA standards regulating fine particulate
matter pollution.
In addition to Kaufman and Miller, the study
included researchers from the UW School of
Medicine and the School of Public Health and
Community Medicine, the Fred Hutchinson Cancer
Research Center, and Harborview Medical Center,
all in Seattle.
NOTE: To determine the average annual concentration
of fine particulate matter for a particular
city or county, visit the EPA's Air Trends
Web site and look for "PM 2.5 Wtd AM" in
the tables provided. The most recent data available
from the EPA is from 2005. http://www.epa.gov/airtrends/factbook.html
Contact: Justin Reedy
University
of Washington
Article URL: http://www.medicalnewstoday.com/medicalnews.php?newsid=62081 |