Those numbers are startling, and that’s the point. University of Chicago researchers wanted to make air quality measurements less abstract and more relatable — and what is more relatable than years of life?

The pollution most responsible for shortening lives consists of the tiniest airborne particles, called PM2.5. They are small enough to penetrate deep into the lungs and bloodstream, causing breathing and cardiovascular problems, cancer and possibly even dementia. They’re bad for healthy people and terrible for young children, the elderly and anyone who already has heart or respiratory problems.

The particles are light enough to hang in the air for a long time and travel with the wind, which is why wildfires in California triggered air quality alerts and forced school closings many miles away.

The Chicago team started with satellite data that mapped the annual PM2.5 concentration in air all over the world, from 1998 to 2016.

They filtered out the particles that came from dust and sea salt — less than a fifth of the total — so they could focus on the majority, which are generated by vehicle exhaust, combustion of fossil fuels, burning crops and other human activity.

Then they calculated how much longer people would live if the air they breathe had fewer — or none — of these particles. The result of the project is the Air Quality Life Index.

These numbers are a warning, however, not a death sentence.

They reflect what could be expected if people spend their entire lives breathing the average amount of pollution that was measured in their region during each year in the study. People can change the air, and in many places they have.

“The present is not destiny,” said Michael Greenstone, director of the Energy Policy Institute and lead author of the report based on this research. “When you look around the world, forceful policy can really change air quality and lengthen people’s lives.”

Change in air quality since 1998

Better in 2016

Worse

Change in air quality since 1998

Better in 2016

Worse

Change in air quality since 1998

Better in 2016

Worse

Change in air quality since 1998

Better in 2016

Worse

Change in air quality since 1998

Better in 2016

Worse

Nepal, India, Bangladesh, Singapore and China have recorded the highest increase in air pollution since 1998...

6 years lost

5.3

India

4

3.9

China

2

0

1998

2016

...while Mexico, Andorra, Lithuania, Belgium and Belize have improved their air quality the most.

6 years lost

4

2.7

2

1.2

Mexico

0

1998

2016

Nepal, India, Bangladesh, Singapore and China have recorded the highest increase in air pollution since 1998...

6 years lost

5.3

India

3.9

China

4

2.8

2

0

1998

2016

...while Mexico, Andorra, Lithuania, Belgium and Belize have improved their air quality the most.

6 years lost

4

2.7

2

1.2

Mexico

0

1998

2016

Nepal, India, Bangladesh, Singapore and China have recorded the highest increase in air pollution since 1998...

...while Mexico, Andorra, Lithuania, Belgium and Belize have improved their air quality the most.

6 years lost

6 years lost

5.3

India

4

4

3.9

China

2.7

2

2

1.2

Mexico

0

0

1998

2016

1998

2016

Nepal, India, Bangladesh, Singapore and China have recorded the highest increase in air pollution since 1998...

...while Mexico, Andorra, Lithuania, Belgium and Belize have improved their air quality the most.

6 years lost

6 years lost

5.3

India

4

4

3.9

China

2.7

2

2

1.2

Mexico

0

0

1998

2016

1998

2016

Nepal, India, Bangladesh, Singapore and China have recorded the highest increase in air pollution since 1998...

...while Mexico, Andorra, Lithuania, Belgium and Belize have improved their air quality the most.

6 years lost

6 years lost

5.3

India

4

4

3.9

China

2.7

2

2

1.2

Mexico

0

0

1998

2016

1998

2016

China: Coal heaters and a war on pollution

One example is China, which is notorious for its coal addiction and air pollution. It is also where the Chicago project originated.

In the early 2010s, Greenstone researched communities along the Huai River, which cuts a huge, horizontal path through the middle of the country.

People just to the north and south of the river lived nearly identical lives, except north-siders heated their homes with government-issued coal boilers for decades. They died an average of 3.1 years sooner than their neighbors to the south, who had no heaters.

By comparing fine-particle pollution and lifespan in cities all along both sides of the river, the team was able to link PM2.5 concentration to life expectancy in a 2013 paper.

The next year, the Chinese government responded to public outcry and launched a “war on pollution.” The country closed some coal mines, limited industry such as steel-making, insisted that cities reduce emissions, banned new coal-burning power plants in polluted areas and restricted vehicle traffic.

In four years, the country’s most populated areas cut PM2.5 concentrations by an average of 32 percent, according to ground monitors. Last year alone, Beijing’s pollution reportedly dropped 20 percent.

India: Awful air and a few signs of change

India, on the other hand, has not yet summoned the momentum to clean its air. A 2016 paper found that air pollution contributes to half a million premature deaths each year.

People in some areas near Delhi, the world’s most polluted metropolis, lose a decade or more in life expectancy.

The stories seem endless and dire. Last year, Delhi’s chief minister called the city “a gas chamber.” This year, after fireworks-filled Diwali celebrations on Nov. 8, Delhi’s air-quality index nearly hit 1,000. (Anything over 300 is “hazardous.”) A 2015 study found that nearly half of the area’s children would develop lung damage by adulthood. “Pollution refugees” are fleeing the area.

However, modest signs of change are appearing.

Delhi just closed its last coal-fired power plant, and it has rules banning construction and limited traffic on particularly bad-air days. Officials in agricultural areas seem to be slowly persuading more farmers to stop burning their fields between seasons, which is a huge contributor to the pollution in nearby Delhi.

United States: Industry and the Clean Air Act

“It’s not true in all places, but in most parts of the U.S., air pollution is largely under control,” Greenstone said.

The Clean Air Act of 1970 and the creation of the Environmental Protection Agency the same year ushered in a wave of enormously successful pollution-control legislation.

EPA monitoring of many sites in 1970 showed that much of the country had poor air quality, especially in heavily populated, industrialized cities. In some places, people were losing six years of life expectancy to fine-particle pollution — similar to modern-day Beijing.

By 1998, the air in most counties was significantly cleaner, and by 2016, nearly every location in the country outside Southern California met the EPA’s air quality standards.

Still, there is a ways to go, sometimes in seemingly random places.

For instance, the city of Fairbanks, Alaska, led the nation in particle pollution in 2016, according to data from the EPA’s ground monitors. The hometown paper, the Daily News-Miner, says the problem is likely emissions from home heating — often wood-burning — in the long winters. (Satellite data shows little pollution over the Fairbanks/North Star borough that year, but that is probably because satellites often can’t penetrate heavy cloud cover.)

California
US average fine-particle pollution expressed as years of life lost
Hover on a line for county data

The worst area for particle pollution in the United States is Southern California, according to the 2016 data, and that is even before the enormous wildfires of the past two years.

Despite strict emissions standards, the Los Angeles area’s huge car-dependent population creates pollution, its sunny weather contributes to it, and its topography and prevailing winds trap it over the region.

Ohio
US average fine-particle pollution expressed as years of life lost
Hover on a line for county data

Second to Southern California are parts of Ohio, where people can expect to lose almost 16 months. Rust Belt cities were historically among the most heavily polluted.

“In the ’60s when there was just totally unrestrained pollution, white-collar workers would bring a second shirt to work and change into it midday because their first shirt was so dirty,” Greenstone said. “These are not the guys who are in the mines, these were guys sitting at their desks.”

Alabama
US average fine-particle pollution expressed as years of life lost
Hover on a line for county data

For decades, Alabama’s air was more similar to that of a Rust Belt city than its Southern neighbors. A 1971 weather phenomenon trapped pollution over Birmingham, a major steel producing city with coal-fired power plants, and the resulting public health emergency triggered federal intervention.

“In the 1970s, the state pretty much ignored the passage of the Clean air Act,” said Kirsten Bryant of Gasp, a Birmingham-based air quality advocacy organization.

Birmingham is still home to a coal-fired power plant that is one of the biggest carbon emitters in the nation, Bryant said. But air quality in the state, like the country, has dramatically improved.

Find your U.S. county

US average fine-particle pollution expressed as years of life lost

About this story

Because we wanted to show the total number of years of life expectancy lost to PM2.5 pollution, our numbers differ from the Air Quality Life Index website’s default settings. Those settings show years lost to pollution that exceeds the World Health Organization’s recommended standard. In other words, those settings allow a certain amount of leeway before starting to count years lost. You can see our numbers on the AQLI site if you choose a custom setting of 100 percent pollution reduction. The difference in all cases is less than a year.

There is debate as to whether there is a “safe” level of particle pollution. Last year, a large study by Harvard’s T.H. Chan School of Public Health concluded that there is not, and many scientists agree. Others say pollution below the WHO standard may be less harmful. For consistency, numbers in this story assume that there is no safe level and that PM2.5 reduces life expectancy at the same rate below the WHO threshold as above it.

Air quality information for U.S. locations in 1970 came from EPA monitors; PM2.5 concentrations were estimated using this methodology, because PM2.5 was not directly measured in 1970. The AQLI’s raw dust- and sea salt-removed pollution data is provided by Aaron van Donkelaar.

Additional sources: Qing “Claire” Fan and Vicki Ekstrom High of the Energy Policy Institute at the University of Chicago; Environmental Protection Agency; American Lung Association; environmental engineering professor Glen Cass of California Polytechnic Institute, Gasp.

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