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US President Barack Obama could lose roughly six hours from his expected lifespan after spending three days in India's capital inhaling the world's most toxic air.
Air Force One descended through an acrid smog when it landed in New Delhi on Sunday. A day later, haze obscured the visibility of fighter jets flying over Obama and Prime Minister Narendra Modi as they watched the Republic Day parade, the ceremonial centrepiece of his visit.
Delhi has the world's highest levels of PM2.5 - tiny, toxic particles that lead to respiratory diseases, lung cancer and heart attacks. The Indian capital averaged 153 micrograms per cubic meter in 2013, the World Health Organization said in May, citing government data. That's 15 times more than the average annual exposure recommended by the WHO.
India as a whole is home to 11 of the top 20 cities on the planet with the worst air quality, according to data from the WHO, which collected pollution levels from 1,600 metropolitan areas between 2008 to 2013. The worst US city was Fresno, California, which came 162nd on the list. Over the past two days, PM2.5 levels in Delhi have averaged between 78 to 84 micrograms per cubic meter, according to data collected by India's Ministry of Earth Sciences. The forecast for Jan. 27, when Obama departs, is 84 micrograms.
Those levels translate roughly into an estimated loss of 2 hours a day in life expectancy, said David Spiegelhalter, a statistician at the University of Cambridge, who specialises in quantifying risk in a way that is understandable to the public.
"That's roughly eight cigarettes a day," Spiegelhalter said in an e-mailed response to questions. "I think Delhi is a wonderful city, but this pollution is harming its residents."
India says this week's levels aren't that bad. The government classifies any reading from 60 to 90 micrograms over a 24-year period as "satisfactory," which means they "may cause minor breathing discomfort to sensitive people."
"We weren't concerned about bringing the president here for these meetings," John Podesta, Obama's climate counsellor, told reporters Monday at a briefing in New Delhi. "The president has travelled to many places where the air is bad for one reason or other," including Beijing, he said.
In recent years, India's has seen readings exceed 500 micrograms, a level that doesn't even make it on US charts, according to data from India's Central Pollution Control Board.
Back in Washington, the 24-hour average was 9.1 micrograms, classified as "good" by the U.S. government's AirNow system. Beijing, by contrast, has had a worse week. The latest 24-hour average in China's capital was 174 micrograms, though the reading dropped to 8 micrograms as of 1 pm local time near Tiananmen Square on Monday, according to the Beijing Municipal Environmental Monitoring Center.
Action plan
Obama, who said he stopped smoking about eight years ago, said on Sunday India and the US will start "new joint projects to improve air quality in Indian cities." In a briefing with Modi, both leaders pledged to cooperate more closely on clean energy and climate change. The U.S. is the world's second-biggest carbon dioxide emitter, while India is third.
Podesta said that the clean-energy agreements reached between Obama and Modi will have the added benefit of helping public health by improving air quality.
Despite the talk, there's little Washington or even Delhi officials can do until India's oil refiners are able to start producing cleaner fuels in 2020.
Diesel engines
Vehicles with diesel engines, which proliferated as successive governments subsidised the cost of the fuel, aren't able to install filters to scrub exhaust gases because local fuels carry too much sulphur. As a result, those cars can pump out exhaust gases with 10 times the carcinogenic particles found in gasoline exhaust.
While Modi ended state control on diesel pricing in October, the ratio of diesel to gasoline vehicles running on Indian roads is far greater than in China or the U.S. India expects its refiners to be able to supply high-quality Euro-VI fuels nationwide by 2020, according to Saurabh Chandra, the oil ministry's top bureaucrat.
PM2.5 refers to tiny airborne particles and liquid droplets measuring less than 2.5 micrometers or one-thirtieth the width of a strand of hair. Because they're so small, they penetrate deep into the lungs and pass into the blood stream, according to the U.S. Environmental Protection Agency.
Pressure building
The World Health Organization classifies PM2.5 as a Group 1 carcinogen, similar to asbestos and tobacco. Short-term spikes can kill, triggering strokes, heart failure and asthma attacks, according to the American Lung Association.
Shortened life spans of the urban population because of air pollution cost India $18 billion annually, according to a World Bank report in June. Whether that spurs Modi to take more action remains to be seen. The Indian leader was asked Jan. 25 if his country felt pressure to act more aggressively on environmental issues.
"When we think about the future generations and what kind of a world we are going to give them, then there is pressure," he replied. "India is an independent country and there is no pressure on us from any country or any person."
