And as usual, it's the communities that are least responsible for it that suffer the most.

A dog wears a respirator. (Photo: Josh Edelson/AFP/Getty Images)

Air pollution is a particularly covert killer. Sometimes smog burns our throats and sears our eyes, but just as often it enters the body unnoticed; a deep breath carries invisible gases and fine particles into the lungs where they hit the bloodstream and wreak havoc on our cardiovascular, circulatory, and respiratory systems. Air pollution has well-documented links to asthma, lung and heart diseases, birth defects, and a slew of other negative health outcomes. And now a new study, published this week in the European Heart Journal, has found that it also kills twice as many people as previously thought—surpassing even smoking-related deaths.

The study, which combined air pollution exposure data and mortality data to model the risk of death, found that tiny particles of pollution known as PM2.5, kicked up into the atmosphere mainly by the burning of fossil fuels and biomass, agriculture, and industrial operations, are responsible for 8.79 million early deaths every year—some 1.5 million more deaths per year than tobacco.

Researchers have known for decades that exposure to air pollution—and thus its myriad health effects—is not equally distributed. In the United States and abroad, minorities and low-income communities face significantly higher levels of air pollution than whites and wealthier communities. But another new study published this week in the Proceedings of the National Academy of Sciences expanded on that well-known disparity, showing that, while the consumer habits of white Americans were more responsible for causing air pollution, black and hispanic communities were more likely to suffer the consequences.

The authors quantified this inequality by tracking pollution levels, exposure rates, and sources of pollution in various regions of the country, and then looking at consumption rates and consumer spending on goods and services that drive those sources of pollution. (Though fossil fuels and industrial operations may be the primary source of harmful pollutants, those operations are driven in large part by consumer demand.)

The research is just the latest addition to a mounting pile of evidence that those least responsible for—and least capable of dealing with—environmental issues and disasters are often the most affected.

1. Air Pollution

Research has found that race, rather than poverty levels, is the strongest predictor of exposure to toxic air pollution. The Environmental Protection Agency, for example, has found that black Americans—regardless of wealth—are exposed to more PM 2.5 than white Americans. One study from 2017 found that race was the strongest predictor of exposure to nitrogen dioxide—an air pollutant emitted by cars, trucks, and power plants. The same study showed that, while nitrogen dioxide exposure across the U.S. fell overall in the decade between 2000 and 2010, black and Hispanic communities still experienced 37 percent higher exposures than whites in 2010, and rates for them had fallen only 3 percent from a decade before.

2. Toxic Waste

Minorities and low-income individuals are more likely to live near facilities that produce and dispose of toxic waste. People of color are almost twice as likely as whites to live within a mile of hazardous chemical facilities, for example, according to a 2016 report from the Center for Effective Government. In addition, plants that serve to treat, store, or dispose of toxic waste are more likely to be installed in neighborhoods that minorities and low-income families call home, according to one 2015 study.

Hazardous facilities located in minority communities also have almost twice the rate of incidents involving the release of toxic chemicals as those located in neighborhoods that are largely white—a concerning statistic given that, historically, it's been harder for communities of color to get the attention and funds they need to clean up toxic waste. Another study from 2014 found that, in the early years of the Environmental Protection Agency's Superfund program, which is responsible for cleaning up contamination due to hazardous waste spills and mismanagement, the agency prioritized the clean-up of sites in more privileged and highly educated communities over those in neighborhoods dominated by minorities.

3. Climate Change

Every community across the U.S. will experience the effects of climate change, whether in the form of rising temperatures, heat waves, droughts, sea level rise, or more intense storms—but it will not affect every community equally. A 2009 report from researchers at the University of California–Berkeley found that African Americans living in Los Angeles are almost twice and likely to die during a heat wave than other demographics, and that jobs in California's agricultural sector, where more than three-quarters of workers are Latino, are expected to disappear and become more dangerous as heat and drought reduce harvests. According to the Brookings Institute, low-income and minority communities are both more vulnerable to natural disasters and extreme weather, which climate change is expected to make more frequent and severe, and less capable of recovering after the fact.

These effects will ripple out across the globe: Roughly a quarter of preventable disease and mortality around the world is linked to poor environmental conditions, according to the United Nations. While the richest, more industrialized countries in the world shoulder the blame for polluting the atmosphere with greenhouse gases and other toxins, poor, developing nations around the world will shoulder the most catastrophic consequences of climate change.