Delhi recorded the highest particulate matter exposure in 2017. (Reuters)

As Delhi reels under high levels of air pollution, a study on Thursday said the city recorded the highest levels of exposure to ultra fine particulate matter, PM 2.5, last year while asserting that outdoor pollution reduced the average life expectancy in the national capital by 1.5 years.

The study, published in the Lancet Planetary Health journal said that Delhi recorded 12,322 deaths due to air pollution last year. Delhi recorded the highest PM 2.5 exposure level followed by Uttar Pradesh, Bihar and Haryana and Rajasthan. There were 6.7 lakh deaths due to outdoor particulate matter air pollution and 4.8 lakh deaths due to household air pollution in India last year, it said.

The national capital registered the highest impact due to exposure to ambient particulate matter PM2.5, among all states, the study said, adding the average life expectancy in Delhi was reduced by 1.5 years due to outdoor air pollution last year.

It claimed that the average life expectancy in India would have been 1.7 years higher if the air pollution level (including both the outdoor and indoor air pollution) were less than the minimal level causing health loss.

The study comes against the backdrop of another one conducted by the Energy Policy Institute at the University of Chicago (EPIC) which claimed that Delhi's air quality during the past two decades was the "most deadly" in 2016 as it reduced the life expectancy of a resident by more than 10 years.

It had also asserted that the Delhi was the second among the 50 most polluted areas of the country.

The study conducted by experts and scientists from the Indian Council of Medical Research (ICMR), Public Health Foundation of India (PHFI), and Institute for Health Metrics and Evaluation (IHME) along with other Indian collaborators and the Union health ministry claimed that one ineight deaths in India last year was attributable to air pollution, which contributes to more disease burden than tobacco use.