The residents of Delhi are likely to lose 11.9 years of their lives if the current levels of air pollution in the city persist, a study by a United States-based think tank said on Tuesday.

The Energy Policy Institute at the University of Chicago said in its latest Air Quality Life Index said that the national capital is the most polluted city in the world and is among areas in India that fare much worse than the country’s average.

The organisation said that fine particulate air pollution shortens the average Indian citizen’s life expectancy by 5.3 years.

Fine particulate air pollution refers to PM2.5, or particulate matter smaller than 2.5 microns in diameter. Such particles are especially dangerous as they are small enough to travel deep into the respiratory system, potentially impairing lung function.

The Energy Policy Institute calculated the reduction in life expectancy on the basis of what the average lifespan would have been if the World Health Organization’s guidelines on fine particulate pollution had been followed.

The global health body’s guidelines state that the annual average PM2.5 concentration should not be higher than 5 micrograms per cubic metre.

The Energy Policy Institute said that the whole of the country’s population lives in areas where the annual average particulate pollution level exceeds the World Health Organization’s guidelines.

It added that 67.4% of the population lives in areas that exceed the country’s own national air quality standard of 40 micrograms per cubic metre.

The report said that in the northern plains, 38.9% of the population is on track to lose 8 years of life expectancy relative to the World Health Organization’s guidelines and 4.5 years relative to the national standard if current pollution levels persist. The study defined the northern plains to include Bihar, Chandigarh, Delhi, Haryana, Punjab, Uttar Pradesh, and West Bengal.

According to the Energy Policy Institute, particulate pollution – measured in terms of life expectancy – is the biggest health threat in India. “In contrast, cardiovascular diseases reduce the average Indian’s life expectancy by about 4.5 years, while child and maternal malnutrition reduce life expectancy by 1.8 years,” the report said.

The think tank said that four South Asian countries – India, Bangladesh, Nepal, and Pakistan – are among the world’s most polluted countries today, with the average resident being exposed to 35% higher particulate pollution levels as compared to the year 2000. It noted that the four countries together account for nearly a quarter of the global population.

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