New Delhi topped the list of the world's most polluted capital cities in in 2018, two environmental monitoring groups reported Tuesday.
A study by Greenpeace and Swiss-based IQ AirVisual found the average amount of fine particulate matter, known as PM2.5, in New Delhi was 113.5 last year, more than double the level in Beijing.
The report said New Delhi's toxic air was caused by vehicle and industrial emissions, smoke from burning rubbish and crop residue, and dust from construction sites.
"Air pollution is the greatest environmental risk to health today, estimated to contribute to 7 million premature deaths every year," the report said. "Polluted air presents the world's 4th leading contributing cause of early deaths, and burdens the global economy with an estimated annual cost of $225 billion."
Fine particles of 2.5 micrometers or less in diameter are extremely hazardous because they get stuck deep inside the lungs. The World Health Organization (WHO) has established a daily mean air quality guideline of 25 micrograms of PM2.5 per cubic meter of air.
Fifteen of the world's 20 most polluted cities are in India, including Ghaziabad and Faridabad, the report found.
"The question which remains to be answered is whether there is enough political will to aggressively fight the health emergency India faces today and move away from polluting fuels and practices," said Greenpeace India spokeswoman Pujarini Sen.
All of the cities that were measured in the Middle East and Africa exceeded WHO's guidelines. Ninety-nine percent of the measured cities in South Asia, 95 percent in Southeast Asia, and nearly 90 percent in East Asia also exceeded the target.
The report is based on air quality data from government and private monitoring networks.