Environment: Studies show air pollution can trigger heart attack, stroke and cognitive decline

Updated On: Feb 17, 2012

Recent studies have shown that air pollution might be more dangerous than we thought – it has major effects on our health.  One study conducted by Jennifer Weuve, et al. investigated the effects of air pollution on older women, and suggested that long term exposure to high levels of air pollution is associated with significantly faster cognitive decline. An effect of 10-ug/mincrement in long-term particulate matter (PM) exposure is cognitively equivalent to aging by approximately two years. In fact, exposure to both small and large particulates was linked to substantial cognitive losses. The study also notes that the pollution levels used in the study are actually comparable to those found in many areas throughout the US.

Another study published in the Journal of the American Medical Association and conducted by French researchers from the Paris Cardiovascular Research Center concluded that short-term exposure to high levels of air pollution may actually trigger heart attacks a few days later. More specifically, main air pollutants like carbon monoxide, nitrogen dioxide and sulphur dioxide were significantly associated with increased risk of heart attack. Ozone was the only air pollutant in the study that was not correlated with an increase in heart attack risk. On average, an increase in 10 micrograms per cubic meter of air was associated with a one to three percent increase in chance of having a heart attack in the next week.

According to Dr Hazrije Mustafic, the researcher leading the project, relative risks for heart attack may be low when looked at from an individual’s point of view, but “if you consider the population view, the entire population in industrialized countries is exposed to air pollution, so the impact on public health is not negligible.”

A third study investigated the effects of air pollution on stroke. Results suggest that exposure to PM2.5 levels, which is considered to be generally safe by the US Environment Protection Agency (EPA), actually increases the risk of ischemic stroke onset within hours of exposure. PM2.5 refers to particles less than 2.5 micrometers in diameter, which are also known as fine particles. They come from a variety of sources, but are commonly released by motor vehicles and power plants. Results indicate that the greatest increase in stroke risk actually occurs about 12 hours after exposure to moderate quality air.  

Dr Murray Mittleman, an associate professor at Harvard Medical School and senior author of the paper, said that the fact that stroke risk was up to 34% greater on days that the EPA considers as relatively safe for most people raises concerns that the agency’s standards may not be enough to protect public health. He also said that “any proposed changes in regulated pollution levels must consider the impact of lower levels on public health.”

Gregory A. Wellenius, lead author of the paper, said that “at levels that the Environmental Protection Agency says are safe, we’re seeing real health effects.” In addition, these effects could be seen “within 12 to 14 hours of when pollution levels went up.”

Still, because the studies cannot prove direct correlation between high levels of air pollution and health defects, it is difficult to say whether air pollution has a direct impact on health. Dr. Robert Brook from the University of Michigan says that “the wrong thing to do is to get alarmed”. He recommends that people do their best to live a healthy lifestyle and control factors such as blood pressure, cholesterol, smoking and exercise.

Report: L.A. air pollution may increase risk of stroke [Los Angeles Times, 15 February 2012]

Report: Air pollution linked to heart and brain risks [New York Times, 15 February 2012]

Report: Air pollution may increase stroke, heart attack risk [CNN, 15 February 2012]

Report: Air pollution linked to cognitive impairment in older women [Washington Post, 13 February 2012]

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