The report comes at a time when former perennial offender China, in response to citizen outrage, has taken steps to clean up its air, closing or reforming factories and reducing its coal consumption in favour of renewable energy. The moves helped improve air quality in Beijing and elsewhere, but at a cost - many poor people were denied coal heat during winter or lost jobs.
The WHO's head of public health, Maria Neira, told Reuters that India should follow China's lead.
"There was a big step at the government level declaring war on air pollution," Neira said. "One of the reasons for that is that the health argument was very strongly presented, and the fact that citizens were really breathing air that was totally unacceptable.
"We would be very happy if we would see a similar movement now in India, which is one of the countries for which we are particularly concerned, although there are good initiatives which can be put in place quickly, still the levels are very high and we would like to see a similar decision and leadership," Neira told Reuters.
Unlike China's muscular reforms, India's efforts to address its growing air pollution problem have been more scattershot, such as the last year's temporary ban by the Supreme Court on fireworks in Delhi during Diwali, the Hindu festival of lights. The court had temporarily blocked the sales of fireworks after the previous year's revelry helped contribute to a toxic air emergency that lasted for days.
The WHO did praise an Indian Government program that has provided 37 million poor women with free gas connections to help them switch from coal or dung-fired clay ovens to cooking gas.
