Hongbin Li on linking air pollution with life expectancy in China

When Beijing issued its first “red alert” on air pollution in December, schools closed, factories shut down and cars were ordered off the road.

Less than two weeks later, a second red alert was issued. Though pollution was not the worst on record, the use of the highest warning level marks the new urgency with which Chinese officials are viewing the environmental and health consequences of rapid economic growth.

Pollution is often accepted as an unavoidable cost of China's industrial and economic boom. But Hongbin Li, the James Liang Director of the China Program, is proving that trade-off is shaving years from people’s lives. In showing that pollution is lowering life expectancies, Li is giving policymakers data that he hopes will lead to action against rising smog levels.

Levels of the smog-causing particles considered most dangerous to human health – PM 2.5 – are currently 10 times higher in China than in the United States. In a study based on data from the 1990s, Li found that people in Northern China lived an average of 5.5 years less due to the polluted air.

And the problem is only getting worse. “Our first study was based on data more than a decade ago,” Li said. “But air pollution has become even more severe and widespread in China in recent years.”

Li returned to his home in Beijing for a few days in November and was reminded of how bad the air has become. “Tears immediately formed in my eyes when I stepped off the plane,” Li recalled of the stinging sensation, noting how he'd been re-sensitized to the problem after spending time outside of China. Li received his PhD from Stanford and was C.V. Starr Professor of Economics at Tsinghua University in Beijing. He returned to Stanford to spend a year as an Academic Visitor at the Stanford Center for International Development, a center at the Stanford Institute for Economic Policy Research, and stayed on as the James Liang Director of the China Program at the Stanford Center on Global Poverty and Development.

Li has found a creative way to measure causality between pollution and mortality using the variation in air quality produced by arbitrary Chinese policy choices made many decades ago. During China’s planned economy period in the 1950s, authorities provided free coal to heat homes and offices.

As it was too expensive to heat the entire nation, this privilege was only given to areas north of the Huai River. The river was chosen as the dividing line as its latitude falls around zero degrees Celsius – the freezing point of water – during the coldest month of the year, January. By the time China had the financial resources to pay for heating across the nation, the Southern regions were too populated to retroactively introduce boiler heating infrastructure. As a result, pollution remains much worse in the North than in the South.

The division line creates the basis for a natural experiment – similar people on both sides of the river are exposed to very different pollution levels. Comparing the life expectancy of the two groups of people lets Li identify to what extent air pollution is cutting lives short.

The costs of air pollution are extraordinary and extend beyond health effects to economic ones, Li explains. Smog has become such a pervasive aspect of daily life that Chinese weather apps imbed a measure of air quality. According to Li, checking smog levels has become a routine part of how people plan their day, with many choosing to stay home on particularly hazy days.

Less time spent outdoors can mean fewer shopping purchases and a shorter life expectancy can mean shortened careers. Schools in Beijing were closed for a record six days in one month under December’s two red alerts. None of this bodes well for China’s economy.

Though welcomed winds can clear the air enough to end a red alert, pollution in China continues to rise. But improved emissions policies could make it safer for the country to take a deep breath.

Please note that prior to May 2019, the Stanford King Center on Global Development was known as the Stanford Center on Global Poverty and Development.