March 22, 2012

Air Pollution A Danger to More than Lungs

Just a small spike in pollution can trigger an increase in strokes and heart attacks.

It's now official. On days when air pollution is at its highest, heart attacks increase.

While it has been well established that long-term exposure to air pollution means an increased risk of heart problems, the ability of short-term spikes in air pollution to trigger heart attacks has only been a suspicion. Some studies have shown a relationship; others haven't.

Air pollution spikes frequently occur as a result of a temperature inversion, when cool air becomes trapped under a blanket of warmer air, preventing the air from mixing and pollutants from dispersing. This can send air pollution levels soaring for days or even weeks at a time. While most common in winter, temperature inversions in summer can be more troubling because they combine elevated pollution with blazing temperatures.

For any of five pollutants, a rise in concentration of 10 micrograms per cubic meter of air meant an increased risk of heart attack in the next week of between one and five percent.

Researchers from the Paris Cardiovascular Research Center combed the literature back to 1948 for all studies investigating the effect of air pollution level and short-term risk of heart attack. Analyzing 34 such studies, they found that the risk of suffering a heart attack within the next week rose slightly as levels of any of five major air pollutants increased. This effect was seen for all the major air pollutants studied except for ozone.

The air pollutants looked at were carbon monoxide, sulfur dioxide, nitrogen dioxide and small particulate matter (soot-like particles) of two sizes, 10 micrometers or less and 2.5 micrometers or less.

For any of these five pollutants, a rise in concentration of 10 micrograms per cubic meter of air meant an increased risk of heart attack in the next week of between one and five percent. And while this increased risk is small compared to traditional risk factors like smoking, they affect everyone. Breathing is mandatory, not a lifestyle choice.

Another study published in Archives of Internal Medicine on February 13 found that the risk of stroke rose from as little as a 24-hour period where the concentration of small particulates (under 2.5 micrometers) in the air rose, even at particulate levels below those deemed safe by the EPA.

Taken together, both the stroke and heart attack studies show how cleaner air would benefit the health of everyone.

They also suggest a need for caution on the part of people at highest risk for heart attack or stroke--including people who already have heart disease or diabetes and the elderly, particularly those who live in urban areas where air pollution is highest. If moving to a locale with cleaner air isn't an option, they need to pay attention to air pollution spikes and alter their activity because of them. This could mean taking it easy on smoggy summer days or limiting car travel during rush-hour, when being caught in a traffic jam will mean breathing increasingly polluted air.

An article on the relationship between air pollutants and heart attacks appears in The Journal of the American Medical Association (JAMA).

NOTE: We regret that we cannot answer personal medical questions.
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