Study links air pollution to heart attacks

By Emily Richmond (contact)

Tuesday, June 12, 2001 | 9:46 a.m.

Clark County residents who smoke, are obese or have heart disease or diabetes could face a greater risk of suffering a heart attack on days when air pollution levels are high, according to a Boston physician whose study was released Monday by the American Heart Association.

Dr. Murray A. Mittleman, the study's author and director of cardiovascular epidemiology at Boston's Beth Israel Deaconess Medical Center, found that the risk of having a heart attack climbed 48 percent two hours after exposure to high levels of microscopic air pollutants. The risk jumped to 62 percent 24 hours after exposure.

Because Nevada has a high rate of adult smokers and people with cardiovascular disease, a large segment of the population is already at risk for a heart attack. When the air pollutants are added to the equation, the risk could be multiplied, Mittleman said.

Nevada ranks 35th in the nation in deaths due to cardiovascular disease and has the second highest rate of adult smokers, said Robin Camacho, spokeswoman for the Nevada office of the American Heart Association.

Nevada's climate also contributes to the risk. When temperatures are high, pollutants become trapped in the air, Mittleman said.

Although the study was limited to patients in Boston, its findings are significant enough to raise concerns elsewhere, Camacho said.

"We're certainly going to be taking a closer look at the study and see what we can learn from it," Camacho said.

Douglas W. Dockery, the study's co-author and a professor of environmental epidemiology at the Harvard School of Public Health, said he focused on the effects of the tiniest, microscopic particulate matter, measuring 2.5 microns or smaller, also known as PM 2.5. The Environmental Protection Agency first issued standards for PM 2.5 in 1997, and the agency has been tracking it since 1999.

The larger particulate matter, called PM 10, is already tracked by the EPA and air quality districts around the world, including Clark County's. The county doesn't track the PM 2.5 level, because it isn't required under federal regulation, Clark County Health District spokeswoman Jennifer Sizemore said.

Known sources of PM 10 include construction dust and pollution generated by rock processing. Sources of PM 2.5 include motor vehicle emissions, power generators, industrial facilities and wood-burning stoves.

Areas with high PM 10 levels already have significant amounts of PM 2.5, because it's included as a subset of the larger measurement, Mittleman said.

The PM 2.5 is actually the most hazardous component of the PM 10 measurement, Dockery said. The tiny particles are so small they can "get past the normal defense mechanisms in the lungs and penetrate deeply into the air exchange regions, or alveoli," Dockery said.

The EPA's standard for PM 10 is 150 microns. Clark County's level was measured this week at 56, which is considered moderate. Clark County enacted stricter air quality standards in January and has launched a new campaign aimed at reducing PM 10s, Sizemore said. The county doesn't yet track the smaller PM 2.5s because it isn't required, she said.

Chris Robinson, director of the Clark County Air Quality Division, declined to comment, because she had not reviewed the heart association's study.

Paul Billings, spokesman for the American Lung Association's Washington, D.C., office, said his organization has also been studying the impact of PM 2.5, and it has found a link between high amounts of the tiny pollutants and mortality rates.

"We welcome the Heart Association's involvement in this emerging area of research," Billings said.

Mittleman suggested people with other risk factors, such as heart disease or diabetes, follow existing health guidelines and avoid exercise outdoors on days with high levels of PM 10. The microscopic PM 2.5 particles can penetrate indoors, but air conditioners are effective at trapping most of the pollutants, Mittleman said.