In the News

February 21, 2022

How to Clear the Air in the Most Polluted Cities on Earth

The Air Quality Life Index is highlighted in Vox.
Siobhan McDonough

The atmosphere has changed in Beijing since the Chinese capital’s last Olympics in 2008. While the Summer Games 14 years ago were meant to be a forward-looking celebration of China taking its place on the world stage, the 2022 Winter Olympics have a markedly dourer tone, hamstrung by Covid-19 and political controversy.

But one aspect of Beijing’s atmosphere has clearly improved: the air itself. While the 2008 Games were marked by some of the worst air quality in Olympic history, China’s “war against pollution” has advanced so much since that Olympians this month could glimpse the previously smog-enshrouded mountains surrounding the city. Air pollution in the capital has decreased by 50 percent since the 2008 Olympics, which if maintained will lead to four years of additional life for the average Beijing resident.

According to the Energy Policy Institute at the University of Chicago (EPIC), global air pollution has decreased since 2011, but that drop is mostly concentrated in China. Most countries across South Asia, Southeast Asia, and sub-Saharan Africa have experienced steady or increased air pollution in recent decades. The situation is especially bad throughout much of India: As of 2020, nine of the world’s 10 most polluted cities were in India, and people throughout the Indo-Gangetic plain could expect to live as much as nine years longer if pollution was reduced to the WHO guideline numbers.

To some degree, the increase in air pollution is a byproduct of economic development: more cars, more energy, more growth. But severe air pollution isn’t an immutable law of nature. From 2013 to 2019, China reduced its particulate pollution by 29 percent by using a suite of policies, including implementing new and better-enforced emissions standards for coal plants, limiting the building of new coal plants, restricting vehicles on roads in large cities, and increasing renewable energy. “If these reductions are sustained,” states an EPIC report from 2021, “China’s people can expect to live 1.5 years longer.”

“Most of what we know about the impacts of air pollution on health are from short-term exposure studies, so these are studies that take advantage of daily or weekly or sometimes quarterly differences in air pollution concentrations,” says Michael Greenstone, director of EPIC, whose AQLI (Air Quality Life Index) tracks reduced life expectancy from air pollution. Yet, he adds, “the reason we regulate it is to change people’s long-run exposure to air pollution.”

The AQLI estimates are based on a 2013 paper that used a home heating program in China to approximate years of life lost by air pollution. From the 1950s to the 1980s, the Chinese government provided free coal for winter heating for households north of the Huai River, but not south of it. That policy created a natural experiment: Villages north and south of the river were mostly the same, save for increased indoor air pollution in the north because residents could afford to burn more coal there.

Life expectancies in those households north of the Huai River fell by an estimated 5.5 years. The researchers used this data to isolate the effect of air pollution from other potential causes of reduced life expectancy, and created the AQLI index to calculate the impact that different levels of particulate concentration can have on lifespan. Policymakers and the general public can use the AQLI to track how air quality has been affecting life expectancy in different countries and regions over the last 20 years. They’ve discovered that while air pollution shortens lives around the world, its main effects are concentrated in South Asia, Southeast Asia, and sub-Saharan Africa.

While air pollution in Delhi has been bad for decades, the last 20 years have seen air pollution worsen in other areas of India and South and Southeast Asia, as economic growth has translated into increased vehicle and fossil fuel use. In the Central Indian states of Maharashtra and Madhya Pradesh, according to EPIC’s 2021 annual report, “the average person … is now losing an additional 2.5 to 2.9 years of life expectancy” relative to the early 2000s due to air pollution. “Eighty-three percent of the country, by one estimate,” says Santosh Harish, South Asian Air Quality program officer at Open Philanthropy, “breathes air that is worse than the national standards,” which are themselves more lenient than the WHO recommendations.

In neighboring Bangladesh, the average person is losing 5.4 years of life expectancy due to air pollution, much more than 20 years ago. Urbanized regions of Indonesia, such as Jakarta, face similar burdens on life expectancy due to vehicle-related pollution and coal-fired power plants. Forest and peatland fires for agricultural clearance related to palm oil production in Kalimantan and Sumatra affect air quality across Indonesia and throughout Southeast Asia.

Air pollution is a severe health threat in Nigeria, Ghana, and the Democratic Republic of the Congo. In Nigeria, home to over 200 million people, air pollution has reduced life expectancy by 1.5 additional years compared to the early 2000s, caused by vehicles, industrial emissions, waste burning, port pollution, and the operation of diesel generators that are used because of the country’s unreliable electricity supply. As energy consumption in sub-Saharan Africa has grown, air quality has decreased throughout the region, according to the AQLI.

A complementary approach might be market-based policies. “A great way to soften those trade-offs,” Greenstone told me, “is to use market-based regulations, which really minimize the regulatory costs and minimize the impacts on economic growth, and while doing that allow for robust improvements in environmental quality and ultimately people’s health.” The state of Gujarat in India, for example, started an emissions trading program for air pollution in 2019 in which the government sets an emissions cap and companies could buy and sell permits to discharge pollutants, creating an incentive for them to reduce pollutants. This has cut air pollution by roughly 15-20 percent, according to Greenstone; with this success, the government is expanding the plan throughout Gujarat, and a similar program is being implemented by the Indian state of Punjab.

End-of-pipe control measures — which mandate pollution reductions at the source — face some of the same challenges around incentives. These upgrades, which cut conventional pollutants like SO2, are effective at cleaning up the air — though they don’t reduce carbon pollution — without requiring an immediate transition away from coal. That’s important for countries like India where the energy supply is still dominated by coal, and will likely be so for years.

Such policies have been highly effective at cleaning up the air in China and Europe, as well as the US, but Peng notes that regulators pushing for cleaner air need to grapple with “the organized interests from the power generation companies that don’t want to do additional things to increase their costs.” That means governments have to spend time and money on the process of negotiation, along with monitoring and enforcement.

Cultivating public demand for clean air by warning people about its health risks can also drive action by governments and individuals across countries. Greenstone noted how large policy changes in other countries, like China’s “war on pollution,” were influenced by public demand. In a best-case scenario, this can create a virtuous cycle of policymakers, researchers, and other actors — such as what Kejriwal was trying to achieve with his daily tweets on Delhi’s air pollution levels this winter.

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