The study showed that every additional 10 micrograms per cubic meter of PM10 cuts life expectancy by 0.6 years. Using this finding, the researchers showed how particulate pollution slashes life expectancy worldwide, building a map to illustrate just how much longer you could expect to live if your country brought its air quality into line with WHO standards.
India and its immediate neighbors fared even worse than China. Indians could live some four years longer on average, or a combined 4.7 billion life years, if air pollution was reduced to comply with WHO standards.
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For Delhi, its most polluted city, particulate matter reduces life expectancy by a staggering nine years. Bangladesh and Nepal are suffering from 5.16-year and 3.9-year life expectancy penalties, respectively, for their poor air quality.
Other particulate hotspots were the Democratic Republic of the Congo (1.84 years), Tajikistan (2.14 years), and Pakistan (2.49).
The United States and Europe are also affected, particularly in California, which has the dubious honor of containing eight of the US’s 10 most polluted cities, thanks to an unhappy marriage of high population and unfortunate topography that has the effect of trapping pollution.
Residents of Los Angeles would have 8.4 extra months to live if WHO standards were met, while inhabitants of San Diego would have an additional four months. Chicagoans would have about six months.
Scientists have known that particulate matter is particularly dangerous for some time. But parsing the direct impact of exposure has been problematic, with observational data muddied by other socioeconomic factors that often go along with exposure, such as income, diet, smoking, etc.
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After all, it would hardly be ethical to perform a trial that varies the pollution levels of two otherwise similar populations that are separated by a discrete geographical border, and which are generally prohibited from migrating from one area to the other. However, that is pretty much what the Chinese government did, unwittingly, with the Huai River coal policy.
The Huai River policy provided an unusually clear example of a “natural experiment,” said Avraham Ebenstein, a lecturer in the Department of Environmental Economics and Management at Hebrew University of Jerusalem and a co-author of the study.
Ebenstein told Seeker that areas in developing countries that become more polluted because of the development of industry usually also commensurately wealthier as people get industrial jobs. This comes with factors — access to healthcare, better nutrition — that benefit people’s health even as pollution impairs it. Consequently, the link between life expectancy is often understated in developing countries.
Conversely, he added, developed countries build industry in poor areas, with the opposite effect: poorer and thus sicker people live in industrial, increasingly polluted areas, and the link becomes overstated.
“So the Huai River policy let us look at a place where the pollution is different, but it’s not because of industrialization, it’s not because of something that is also creating a wealth difference,” Ebenstein remarked.
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The hukou system, a household registration system peculiar to China that keeps people in particular areas, helped make the researchers’ dataset particularly clean.
“Most people didn’t migrate in China until very recently,” Ebenstein explained. “Almost everyone is still dying in their hukou, where their family’s residence permit was issued in 1953.”
China’s historical limitations on migration mean that causes and dates of death for the residents of a specific town can be compared directly with pollution figures for that town — something that is much, much more difficult with a city like London or New York, where masses of people routinely move in and out at will.
The recent study expands on a 2013 paper that found that life expectancy was cut by about 5.5 years above the Huai River due to pollution. But the new study uses fresh data and covers a population that is eight times greater than in 2013. It notes that the smaller life expectancy cut may reflect China’s progress in investing in green energy and reducing its air pollution.
Ebenstein, who worked with Greenstone on both studies, said that he hopes their findings will shift policy towards a more serious approach to particulate pollution.
“This pollution, it’s not just the mortality rate — anyone who’s lived in a polluted city gets it. Play basketball in Beijing and you get tired immediately,” he said. “This paper should really be the nail in the coffin for people who don’t believe that pollution affects health.”
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