Dirty Truth About Air: Pollution's Effect On Heart Health, Obesity and Fertility

Sarah Baldauf

The political wrangling over environmental matters like greenhouse gases, emissions trading, and energy security often clouds another substantive part of the story: the deleterious health effects of breathing dirty air. Now, scientists and health professionals are looking to draw more attention to that part of the debate. The Environmental Protection Agency highlighted this concern in December when, after reviewing the evidence, it ruled that greenhouse gases are detrimental to human health, particularly because they can aggravate asthma and other respiratory illnesses and can produce longer, more intense heat waves that endanger the poor, sick, and elderly.

Some critics called that ruling a thinly veiled way for the Obama administration to regulate the gases associated with climate change and advance campaign promises to create "green jobs" while sidestepping the legislative process. Such a move "would debilitate an industry that really drives the economy of this country," says Charles Drevna, president of the National Petrochemical and Refiners Association.

Politics aside, a growing body of research is revealing just how damaging some air pollutants appear to be to the health of the American public. For decades, clean-air advocates have worked to improve the nation's air quality, and the health risks a particular individual might face directly from breathing polluted air are low. But research consistently is finding that spread out over a given population--be it residents of a certain city or those with a particular disease--the quality of the air has a very significant impact on public health.

High potential. When vehicles, factories, power plants, and other machines burn fuel, the chemicals they release into the atmosphere react with one another (and other compounds in the air) in ways that can amplify health hazards. "Greenhouse gases actually increase air pollution and therefore [raise the] potential for more adverse events for people with pre-existing respiratory conditions or heart conditions," says Kent Pinkerton, chair of the environmental health policy committee at the American Thoracic Society.

A constellation of air pollutants chip away at human health, and the EPA's ruling dealt only with greenhouse gases, including carbon dioxide, nitrous oxide, and methane. But another major concern of researchers who study the effects of air pollution is the havoc particulates wreak on human health. Particulates are microscopic bits, solid or liquid, that are released largely as the byproducts of burning fuel or other substances, though they can occur naturally as well. Norman Edelman, a pulmonologist who is the chief medical officer at the American Lung Association, says that "over the last 20 years, it's become apparent that particulates are especially bad actors to the lung and heart."

The fine and ultrafine particulates in air pollution are so small that they can slip by the respiratory system's defenses. (Fine particulates are about one thirtieth of the width of a human hair, according to the EPA; ultrafine particulates can be one twenty-fifth as large as fine ones.) Over time, particulate exposure can raise rates of chronic obstructive pulmonary disease, lung cancer deaths, and asthma attacks.

But concerns go beyond the respiratory system. "People thought that when we inhale pollutants, the lung was the main target, but the lung is surprisingly resilient. It turns out the cardiovascular effects are predominant," says Aruni Bhatnagar, an environmental cardiology researcher at the University of Louisville. One major study, which followed subjects for 16 years, found that people living in cities with higher levels of fine particulates were at greater risk of cardiovascular death. A difference of 10 micrograms per cubic meter increased the risk of dying from ischemic heart disease (narrowed arteries) by 18 percent, arrhythmia by 13 percent, and cardiac arrest by 21 percent, the study said.

Longevity. In a landmark 1993 study of six American cities, researchers found that even after adjusting for the most damaging threats to longevity, like cigarette smoking, residents from the cities with the worst air pollution were 26 percent more likely to die during the follow-up period (14 to 16 years) than residents of the cities with the lowest air pollution. Some of the same researchers showed in a study published last year in the New England Journal of Medicine that U.S. efforts to improve air quality over recent decades, measured by reductions in fine particulates in 51 American cities, led to a five-month boost in the average life expectancy of their residents.

Unlike lifestyle changes--say, quitting smoking or taking up jogging--there is little an individual can do about the quality of the air. "This is not even a voluntary thing; there is no escape," says Bhatnagar. The risks from merely living in areas with the worst air--like Pittsburgh, Los Angeles, and New York, according to the American Lung Association's 2009 "State of the Air" report--equate to smoking two cigarettes a day, he says. Even short-term exposure can be hazardous. Research shows spikes in cardiac deaths, emergency room visits, and hospital admissions in the hours and days that follow a spike in cities' levels of particulate matter.

One question that has the scientific community's focus is exactly who is most vulnerable to the effects of bad air. Emerging research suggests one group that could be at risk is those who are overweight or obese--even young adults. Considering the number of people in the United States who fit those designations, this risk is "an important public-health issue," says Stephanie London, an internist and a senior investigator at the National Institute of Environmental Health Sciences. Her research found that among 18-to-35-year-olds exposed to ozone, a greater body mass index correlated with diminished lung function. Air pollution has been found to exacerbate health problems in the young, the elderly, and those with such chronic conditions as respiratory disease, heart disease, and diabetes. But it might also actually cause disease. Separate research by London found that kids ages 9 to 16 who played at least three sports and lived in areas with high ozone concentrations had a 30 percent increased chance of developing asthma. And other emerging research indicates that infants whose mothers were exposed to air pollutants while pregnant might be at a slightly greater risk of low birth weight, pre-term birth, and even death. Researchers also are investigating air pollution's effects on miscarriage rates and sperm quality in men.

Exactly how air pollutants cause harm is not entirely clear, but the predominant belief is that the body's inflammatory response becomes chronically activated. Pollutants also appear to trigger changes in the part of the nervous system that regulates blood pressure and blood vessel constriction. Some evidence suggests that the smallest particulates might even pass into the bloodstream--just like oxygen--and damage other organs directly.

The growing body of research and the EPA ruling are drawing attention to how what's in the air affects what happens inside the body. Although some observers fear that the cost of cleaning up the air might hinder an economic recovery, health investigators argue against losing sight of health effects. "We need to not step backward because we're in [economic] survival mode," says Robert Brook, a University of Michigan cardiologist who researches the health effects of air pollution. "Reduction in ozone [and other pollutants] will likely lead to improvements in rates of lung and heart disease," he adds. A powerful tool, indeed, to reduce the disease burden--and related costs--of some of America's major killers.

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Environment - Dirty Truth About Air: Pollution's Effect On Heart Health Obesity and Fertility | Sarah Baldauf