Pollution may increase heart attack risk for obese

Feb 7 2006

A University of Alberta researcher believes obese humans face same dangers from diesel exhaust and coal emissions.

Obese individuals at risk of diabetes are in danger of cardiovascular events, such as heart attacks, when exposed to pollution from diesel exhaust or power plant emissions, says a University of Alberta researcher who is sounding the alarm in a study offering the first direct proof of that relationship.

"There is a growing body of evidence that exposure to fine particulate matter--the small stuff you can't see--correlates to diseases in the public," says Dr. Jim Russell, a researcher at the U of A's Alberta Institute for Human Nutrition. "Our research helps connect the dots and get at the mechanisms that put people at risk. It has major implications for public health and environmental policy."

The growing pandemic of obesity, pre-diabetic metabolic syndrome and Type 2 diabetes is creating a new generation of cardiovascular dysfunction--such as heart disease or stroke--that is increasingly influenced by the external environment. Russell's research team--including the U of A's Dr. Spencer Proctor and Sandra Kelly, collaborating with Dr. Kevin Dreher of the U.S. Environmental Protection Agency--specifically studied fine particulate matter measuring less than 2.5 microns in diameter.

They compared rats that are obese and insulin resistant from a unique strain Russell developed in his lab in 1978--and come with all the regular cardiovascular complications--with lean and metabolically normal rats. In terms of metabolism and heart disease, the animals, says Russell, "behave in every respect like your obese human."

Using particles collected downstream of the emission controls of a power plant in Birmingham, Alabama burning low sulfur residual oil, arteries of both rat groups were exposed to the pollution. On the second exposure, the arteries of the obese rat contracted directly and "very strongly," compared to the lean rats, says Russell, also a professor emeritus in the Faculty of Medicine and Dentistry. "I was surprised by the findings because I didn't think they would be as dramatic as they were," he said, adding that although there is a lot of emphasis on the connection between lung cancer and pollution, more attention should be paid to the impact it has on the cardiovascular system. "It raises a real question about the effects of these pollutants, especially in vulnerable members of the population".

"This is something that needs to be debated publicly. Some efforts have been made to filter the particles but it is what you can't see that is worrisome. Alberta gets almost all its electrical energy from burning coal and this is seen as a controversial strategy in other parts of the country, such as Ontario. This is not an esoteric concern."

This demonstration of a direct link between the prediabetic insulin resistant state and cardiovascular sensitivity to fine particulate matter contributes to the growing weight of evidence that this pollution represents a significant public health risk, says Russell.