New research links “safe” levels of air pollution to premature death.
Every day, you inhale thousands of gallons of air — mostly nitrogen, oxygen, and a smattering of other gases. But that air also contains tiny particles spewed from power plants, industrial factories, and vehicles. These pollutants can trigger heart attacks, strokes, and irregular heart rhythms, especially in people who already have or who are at risk for heart disease.
And even though the air we breathe is much cleaner today than it was in the 1970s, there’s still room for improvement. In fact, a major Harvard study recently found that air pollution kills thousands of people in the United States each year, even at pollution levels currently allowed by the Environmental Protection Agency (see “Something in the air: Regulating pollution”).
“If we cleaned up the air even more, we could prolong people’s lives,” says Dr. Jeffrey Drazen, editor-in-chief of The New England Journal of Medicine, where the study (and an editorial he co-authored) was published on June 29, 2017.
Something in the air: Regulating pollution
In 1970, the Clean Air Act was amended to institute National Ambient Air Quality Standards (NAAQS), which set exposure limits for six major air pollutants. Most comes from car and truck exhaust, power plants, refineries, and other industrial factories. Wildfires and wood-burning stoves also contribute to air pollution.
From a health standpoint, the most worrisome pollutants are tiny soot particles that are so small that 100 could sit side-by-side across the period at the end of this sentence and still have room for more. They are called particulate matter less than 2.5 micrometers, or PM2.5 for short. Ground-level ozone, which forms when gas pollutants react with heat and sunlight, is also a concern.
The current NAAQS for particle pollutants, last updated in 2012, set the yearly average level of PM2.5 at 12 micrograms per cubic meter. In 2015, the ozone standard was set at 70 parts per billion (ppb), but the study described in the main text used a cutoff of 50 ppb.
Air pollution’s deadly toll
The study included data from nearly all of the nation’s Medicare recipients — some 60 million people, all ages 65 or older. Using information from federal air monitoring stations and satellites, researchers compiled a detailed picture of air pollution levels, pinpointing areas down to individual ZIP codes. They then analyzed the impact of very low levels of air pollution on death rates.
The results suggest that lowering the levels of tiny particulate matter (known as PM2.5) nationwide by just one microgram per cubic meter of air below current standards could save as many as 12,000 lives each year, the researchers concluded. Similarly, lowering ozone levels by just one part per billion nationwide could save an estimated 1,900 lives each year.
While the researchers didn’t report the causes of death, cardiovascular disease accounts for one of every three deaths in this country. And there’s a clear, established biological link between air pollution and heart disease, notes Dr. Drazen. Fine particles pass through the lungs into the circulation, activating immune cells called macrophages. These cells are intimately involved in the creation of artery-clogging plaque, which interferes with blood flow, potentially triggering a heart attack or stroke, says Dr. Drazen, who is also a professor of environmental health at the Harvard T.H. Chan School of Public Health. The evidence is strong enough that the American Heart Association has advocated for measures that lower Americans’ exposure to air pollution and for more research on the impact of air pollution on public health.
Steps toward solutions
To limit your exposure to air pollution, avoid exercising outdoors near busy roads or industrial areas. Older people and those with asthma or other lung conditions may want to keep tabs on the local air quality index, a color-coded scale for pollution levels that’s often reported by local news outlets; you can also find it at http://www.epa.gov/airnow.
In addition, you can take steps to reduce pollution by bicycling or walking instead of driving when possible, and by purchasing a hybrid or electric car, says Dr. Drazen. Another suggestion: choose nonpolluting renewable energy from your local electricity supplier — an option that’s available many places in the United States. “If we all work together to support legislation that helps clean up the air, that will be in everyone’s best interest,” says Dr. Drazen.
Invisible but audible: Noise pollution hazards
Trains, planes, and automobiles generate not only air pollution, but also a lot of noise. A number of studies suggest that chronic exposure to environmental noise — such as traffic and aircraft noise — may raise blood pressure and the risk of cardiovascular events. A 2015 report in Environmental Research that pooled findings from 10 studies suggested that every 10-decibel (dB) increase in noise above that of an average conversation noise level (50 dB) might slightly raise a person’s risk of heart disease. The cumulative effect of excess noise may increase stress hormones and may also disrupt sleep, both of which can contribute to heart disease, experts say.