Greenpeace has estimated that air pollution in India caused about 3,280 premature deaths a day in 2015 compared to 3,230 in China, relying on disease burden statistics generated by the Institute of Health Metrics at the University of Washington in the US.

These estimates, when compared to figures for 2012 released by the France-based International Energy Agency (IEA) earlier this year, suggest that air-pollution control measures China has initiated since 2011, have lowered its premature deaths associated with air pollution.

The IEA report released in June this year had suggested that indoor and outdoor air pollution had led to about 160 deaths per 100,000 people in China in 2012, while the corresponding figures for India was about 130 per 100,000 people. The report had placed the highest toll in Georgia - about 280 deaths per 100,000 people.

"We're pointing out that things have changed since then," Sunil Dahiya, a Greenpeace campaigner said. China has since 2011 set new emissions standards for coal-fired thermal power plants, imposed caps on coal consumption in specific regions, regulated biomass burning and encouraged public transport, he said.

The estimates are based on mathematical disease burden models that combine multiple factors such as air pollution data, population distribution, and the risks of premature deaths from exposure to polluted air.

The Institute of Health Metrics has been involved in generating illness data worldwide under its Global Disease Burden research initiative.

"The new estimates mean that even though China overall emits more greenhouse gases than India, personal exposure to air pollution to an average person is higher in India than in China," Dahiya said. "It is time India also treats air pollution as a national health emergency and takes similar steps."

A report released at the UN climate change conference in Marrakech, Morocco, earlier this week had estimated China's net greenhouse gas emissions in 2015 to be about about 10.4 billion tonnes (29 per cent of the total global emissions), compared to India's 2.3 billion tonnes (six per cent of total global emissions.)

The New Delhi-based non-government Centre for Science and Environment has also in the past expressed concern about rising air pollution levels and the need for India to initiate long-term measures, including taking steps to curb the proliferation of private vehicles and encourage public transport.

Environmental scientists have attributed air pollution in India to vehicular emissions, including diesel-exhausts from heavy-duty vehicles, thermal power plants, construction dust, and crop stubble burning, among other factors.

India's plans to expand coal production in the near future has been viewed with concern as it could add to pollution. Greenpeace has also called for a national action plan to reduce dependence on coal-fired power plants, expanding public transport networks among other steps to curb air pollution.