WEDNESDAY, Nov. 12, 2008 (Health.com) — Inhaling air pollution during your daily routine—both inside and outside your home—appears to cause a small rise in blood pressure and have an impact on blood vessel function, according to a study presented at the American Heart Association meeting in New Orleans.
These short-term changes may help explain why long-term exposure to air pollution is linked to a greater risk of heart attack and death due to heart disease.
The researchers looked specifically at particulate matter, a type of air pollution that is smaller than 2.5 microns. (A human hair, by comparison, has a diameter of about 100 microns.) These tiny particles can be inhaled deep in the lungs and are more dangerous than larger particles, which tend to be trapped in the nose or upper airways and sneezed or coughed out of the body.
“Clearly the air pollution that you are exposed to on a regular basis affects your blood vessel function and puts you at a higher risk of cardiovascular disease,” says Robert Bard, a research associate at the University of Michigan in Ann Arbor.
In a three-year study, which was part of a larger Environmental Protection Agency (EPA) analysis, Bard and his colleagues asked 65 men and women from Detroit to wear an air-pollution-sensing vest for five consecutive days in the summer and five consecutive days in the winter. (The volunteers did take the vest off while sleeping and showering, but were told to place it nearby).
Sensors were used to make sure the volunteers wore the bulky vests, which hummed with continuously running pumps, Bard says.
The researchers also measured pollution inside and outside the study participants' homes, as well as at the local EPA pollution-monitoring station. At the end of each day, the researchers visited the Detroit residents, who were mostly African American or Hispanic, and measured their blood pressure and other heart functions. The volunteers were anywhere from 19 to 80 years old, with an average age of 45, and they weren’t necessarily healthy; many were overweight or had heart disease, Bard says.
A personal increase in air-pollution exposure from sources both inside and outside the home seemed to affect blood pressure and blood vessel function.
When daily exposure increased by 10 micrograms per cubic meter, there was a 1.6-point rise in systolic blood pressure the next day, and an 18% greater narrowing of a blood vessel in the arm—a type of constriction that measures blood vessel function—about two days later. Pollution measured by the local EPA monitoring station was linked to a change in blood vessel function, but not a rise in blood pressure.
Bard and his colleagues excluded people who smoked or those who lived with smokers, but the vest sensors suggested that about 30% were still exposed to secondhand smoke at some point during the study.
The researchers think that personal exposure to air pollution inside and outside the home may affect health in a different way than, or in addition to, air pollution monitored in the local community.
The study is “very provocative,” says George Thurston, ScD, a professor of environmental medicine at New York University School of Medicine. However, he also says that it raises a lot of questions because of the inconsistency between the personal exposure and local exposure.
The main source of indoor air pollution is smoking, Thurston explains, but there are many other sources too. For example, stirring up dust, lighting a candle, turning on a stove, or spraying an aerosol can all increase particulate matter in the air—but they may not necessarily affect one's health, he says.
“I’ve monitored for fine particles in my home with a continuous detector,” Thurston says. The levels were low until his son came home from school, his pets started running around the house, and the stove was turned on.
“Are those particles that are kicked up off the floor as toxic as combustion particles from diesel trucks?” he asks. “There are indoor sources, but they are quite different in their nature from outdoor particles that are primarily from fossil fuel combustion.”
Air pollution inside the home also may be due to particulate matter that seeps inside from outdoors, Thurston suggests: “People open windows, they open doors. These fine particles are almost like gases; they flow right in.”
Analyzing the particulate matter trapped in the vest sensors will help determine what particles are responsible for the blood pressure rise, he says. If they are toxic particles from the combustion of fossil fuels, they should contain sulfates or elemental carbon.
That research is now under way, according to Bard. “The EPA is in the process of evaluating what specifically was in that particulate matter, so they are looking at different organic compounds and substances that may or may not be influencing the changes that we see,” Bard says.
Thurston says there are many ways to avoid air pollution, both indoors and out. He recommends providing good ventilation for stoves, listening for alerts on high pollution days, and avoiding outdoor activity on those days.
“If you have a choice of running on a highly trafficked road or running through a park with no traffic, choose to go the extra little distance and go to the place that is away from the pollution sources," Thurston says. If you run along a heavily trafficked road, it can help to make sure the wind is blowing pollution away from you rather than toward you.
Some new cars even have filter systems that help remove particles. According to Thurston, people spend 6% of their time commuting and get about 60% of particulate exposure during their commute.
“If you’re in traffic, you’re going to get exposed,” he says. “Being stuck in traffic is not good for your health, both from a stress and air-pollution exposure point of view.”