MONDAY, March 11, 2002 (HealthDayNews) -- A brotherly cross-border collaboration has produced a vivid picture of how polluted air causes a narrowing of blood vessels that can contribute to the risk of heart attack and stroke in healthy people.
On the American side is Dr. Robert D. Brook, assistant professor of medicine at the University of Michigan. On the Canadian side is his older brother, Jeffrey R. Brook, assistant professor of public health at the University of Toronto and a research scientist with Environment Canada, that country's equivalent of the U.S. Environmental Protection Agency.
Together, a paper in the journal Circulation says they have shown that a two-hour exposure to air heavy with fine particles and ozone can narrow the arteries of healthy people by 2 percent to 4 percent. It's a narrowing that, in technical terms, Jeffrey Brook describes as "a vascular response that is intuitively linked to cardiac outcomes."
While that response might not seem like much, it involved a brief exposure to polluted air by healthy individuals, Jeffrey Brook notes. It raises the question of what happens with long-term exposures -- such as a lifetime in a polluted city -- or in people who already have arterial problems.
The study got started because "I come from the air pollution and health research area, and he [Robert Brook] is an M.D. involved in hypertension and cardiology," Jeffrey Brook says. "I was sharing with him the types of results we have seen over the last four or five years. We had some leisurely discussions, and he mentioned some measurements techniques that were simple and noninvasive that we could use in the experiments we were doing."
"We had this nice little symbiosis," Robert Brook says. "I had a technical mechanism to look at blood vessels, and he had a technique to explore the exposure of humans to air pollution. So, we decided to launch this experiment."
They had 25 healthy volunteers go into chambers where they breathed air with measured amounts of the fine particles that come from car engine exhausts, power plants and industrial plants, and of ozone, the poisonous oxygen molecule found in polluted air.
The technology they used was high-resolution vascular ultrasonography, which measures even small changes in blood vessels. The University of Toronto, where the work was done, is one of the few facilities that can expose volunteers to a precisely calibrated level of air pollution.
The study is noteworthy not only because of the technology, but also because it's the first to show how healthy people react to normal pollution levels, Jeffrey Brook says.
"There have been studies of animals in chambers showing dramatic effects, some at high levels of pollution, some at exposure levels comparable to what humans breathe," he says. "But there haven't been a lot of controlled studies in which humans were monitored over time with exposure to ambient levels of pollution."
The changes measured in the trial were statistically significant, and "they highlight that the common levels of air pollution that occur throughout the world can affect even healthy people," Robert Brook says. "They may have chronic, long-term effects in healthy people."
The results provide a physical explanation for the kind of damage to the cardiovascular system described last week in a report in the Journal of the American Medical Association, Jeffrey Brook says. Most articles about the report centered on a finding that a 10-microgram elevation in fine particulate matter increased lung cancer mortality, but the study also found the level caused a 6 percent increase in cardiopulmonary disease.
"Lung cancer got all the splash, but cardiopulmonary effects were there," Jeffrey Brook says.
What To Do
You can't stop breathing, but you can limit exposure as much as possible during days of heavy pollution, Robert Brooks says. "That applies especially to the elderly and those with chronic conditions such as diabetes and heart disease," he says.
You can learn about some of the nasty things in our air and what they are doing to you from the American Heart Association or the U.S. Environmental Protection Agency.
