Breathing regular air in America kills thousands of people every year


There is no safe level of air pollution.

That's the finding of a 12-year study published in the New England Journal of Medicine looking at health records from nearly 61 million people on Medicare combined with a databank of pollution readings.


For every increase of 10 micrograms of a key type of pollutant known as PM2.5, death rates among seniors rose 7.3%. That's the equivalent of 120,000 deaths, said Qian Di, a doctoral student at the Harvard T.H. Chan School of Public Health and one of the study authors. The effects were the strongest for low-income Americans and people of color.

To put that figure into perspective, the World Health Organization has recommended a guideline level of 20 micrograms worldwide, which is a massive reduction from many countries that regularly exceed levels of 70 micrograms or more. Over the course of the study, the average levels the researchers observed ranged from about 6 to 16 micrograms.

Even in years when the concentrations of that pollutant in an area were low and approached levels considered "safe," the researchers saw a connection between exposure and death rates, Di and his colleagues wrote in their study.


"It is clear from this study that there is not really a safe level of air pollution," said Brian Christman, who serves as vice chair of the department of medicine at Vanderbilt University Medical Center and was not directly involved in the research.

For years, researchers have known about the close ties between exposure to high levels of pollutants and an uptick in death rates. They've also known that when regions manage to slash pollution levels, fewer people die.

What they were less clear about, however, was how being exposed even to low levels of the particulates could have such drastic consequences over the long term.


"When you have a large study that shows that the current level of air pollution is toxic - I hope that's something we can do something about," Francesca Dominici, a professor of biostatistics at Harvard and another author on the study, told The New York Times.

In addition to studying the well-known pollutant PM2.5, which is known to be harmful because of its ability to penetrate and lodge deep inside the lungs, the researchers also looked at ozone concentrations, and found a similarly worrisome scenario. For every 10 part-per-billion rise in ozone concentration, the mortality rate among the elderly rose by 1.1%, which amounts to roughly 19,000 deaths.

To arrive at their conclusions, they drew from satellite and meteorological data, plus data gathered from close to 4,000 Environmental Protection Agency monitoring stations. Then, they followed their 60 million Medicare recipients and recorded nearly 23 million deaths over roughly a decade.


Average levels of the first pollutant - PM2.5 - ranged from 6 to 16 micrograms over the course of the study, while ozone concentrations ranged from about 36 to 56.

Given the stark findings they observed, the researchers concluded that current US policies are not strict enough to prevent pollution-related deaths. To make a bigger impact, policy makers need to further slash pollution.

"The data indicates that additional effort ... would save lives," said Christman.


The results come at a time when the Trump administration has begun "to dismantle guidelines intended to reduce emissions from coal-fired electricity plants" and may revoke the waiver that allowed California to adopt stricter vehicle emission standards, according to an editorial accompanying the study.

"Revoking this waiver could have the effect of exposing more than 100 million Americans to higher levels of automobile emissions," the Journal warns. "Trump's proposed budget includes crippling cuts to the EPA, including cuts in funding for both federal and state enforcement of regulations. The increased air pollution that would result from loosening current restrictions would have devastating effects on public health."

The particles studied are dangerous because their tiny size - only visible with an electron microscope - allows them to get deep into the lungs to do damage, and from there they can also enter the bloodstream. According to the Environmental Protection Agency, from 2000 to 2015 the average concentration of PM 2.5 pollution nationally has declined by 37 percent thanks to stricter air standards.


According to the new study, the two regions that saw the greatest improvements in air quality were the central and southeastern United States.

Satellite and weather data, computer models and data from 1,928 particle monitoring stations and 1,877 ozone modeling stations were used to estimate exposure over each square kilometer of the country.

The task was so massive the number crunching had to be done by supercomputer over Harvard's Christmas break, Di noted.


Because the database was so large, Di and his colleagues were also able to determine that subgroups, including men, blacks, Asians, Hispanics and people eligible for the Medicaid health plan for the poor faced the highest risk from small particle pollution.

It shows "this is not just a health issue, but a social equality issue as well," said Di, a doctoral student in Harvard's department of environmental health.


SOURCE: New England Journal of Medicine, online June 28, 2017.