Researchers say India's current levels of air pollution representative of a "public health emergency" and called on local and national authorities to take emergency action.

A recent study found that seven out of the 10 most polluted cities in the world are in India, with Gurugram at the top of the list for 2018.

Gurugram is about 30 kilometers southwest of New Delhi, which is ranked at 11, is the world's most polluted country capital and home to more than 20 million people. Other extremely polluted capital cities on the list include Dhaka, in Bangladesh, and Kabul, in Afghanistan.

The study published by AirVisual and Greenpeace revealed that cities in India, and Faisalabad, Pakistan, make up the top five. Among the top 20 polluted cities, a total of 18 are in India, Pakistan and Bangladesh.

Yeb Sano, the executive director of Greenpeace South Asia points out the numerous negative effects, saying that, "in addition to human lives lost, there's an estimated global cost of US$225 billion in lost labor and trillions in medical costs."

Researchers say India's current levels of air pollution representative of a "public health emergency" and called on local and national authorities to take emergency action. Prime Minister Narendra Modi has been criticized for prioritizing the economy over public health and environmental concerns.

#AirPollution is deadly ��



It causes:

- 36% of deaths from #lungcancer

- 34% of deaths from #stroke

- 27% of deaths from #heartdisease



We need clean air for a healthy future!#BreatheLife pic.twitter.com/jCmUqI5nio — WHO South-East Asia (@WHOSEARO) March 6, 2019

The top 92 most-polluted cities measured "unhealthy" levels of PM2.5, a particulate matter used to monitor air quality. The particles can cause many different health complications, including death, by penetrating the lungs and bloodstream. While death is a result in the most extreme cases, an estimated seven million people are estimated to be killed by air pollution every year, according to the World Health Organization (WHO).

Senior analyst for Greenpeace's Global Air Pollution Unit, Lauri Myllyvirta says, "the biggest sources" for high levels of PM2.5 in South Asia," are generally household emissions, industrial emissions... and transport. A lot of households in South Asia rely on solid fuels, sometimes biomass, often coal, for their cooking and heating... and there are often cities with large scale industries with poor emissions controls."

The analyst added that high population both contributes to poor air quality, as well as exacerbates previously stated reasons. While similar emissions may occur in other locations, Myllyvirta says, "because you have far fewer people [there], it doesn't lead to this kind of… catastrophic level of air pollution."

South Asia, being the most populous region in the most densely populated continent on the planet, is also the most affected by pollution.

Elsewhere in Asia, Chinese cities are showing improvements in air quality, with a 12 percent decrease in PM2.5 concentrations in just one year. President Xi Jinping pledged to wage "war" on the country's consistent pollution problems. AirVisual and Greenpeace attribute China's improvements to heightened "air pollution reduction policies," although the country still accounts for 22 of the 50 most polluted cities in the world.