[NEW DELHI] With cities in India and Pakistan ranking among the world’s most polluted, new technologies must be adopted to tackle dangerous levels of winter smog, environmentalists urge.

According to the Swiss IQ Air index, Lahore in Pakistan and Delhi in India have the highest levels of fine particulate matter in the air, known as PM 2.5, of any city – the only two to be rated as “hazardous”.

Lahore, the provincial capital of Punjab, tops the index, with pollution reaching levels ten times higher than those in Shanghai early this week. The pollution is so bad that the huge gray clouds blanketing the region can be seen from space as satellite imagery from NASA Worldview shows.

Northwestern India, which has been battling exceptionally high levels of pollution during the winter months for several decades, blames the situation on fires lit by farmers to burn stubble and prepare the ground for the next sowing.

However, there are other sources of pollution such as vehicular exhaust, industrial emissions and a policy of incinerating municipal waste to produce electricity.

Meanwhile, scientists and environmentalists say that temperature inversion, a major cause of the toxic smog that hangs over the Indo-Gangetic plain during winters, has to be factored into industrial and other development activities across Pakistan, India, Nepal and Bangladesh.

Atmospheric temperature inversion, also known as thermal inversion, traps a layer of cold air near the earth’s surface in winter, interfering with a natural process by which wind and rainfall carry away pollutants.

The longer the inversion lasts, the greater the accumulation of pollution, worsening air quality. In areas with little pollution, the chances of temperature inversions occurring are also fewer.

“It is pointless blaming anyone because, the Indo-Gangetic plain is affected by atmospheric thermal inversion and low wind speeds in winter that is exacerbated by high industrial activity, large populations and farm residue burning,” says Jayanarayan Kuttippurath, a specialist in atmospheric chemistry and physics and associate professor at the Indian Institute of Technology Kharagpur.

Kuttippurath says effective pollution control strategies and technological advancements can help tackle the seasonal pollution surges.

“We know from recent studies that technologies like scrubbers and converters, along with strong environmental policies, can significantly reduce pollutants like sulfur dioxide (SO₂), concentrations of which are high in the winter months,” he explains.

High levels of black carbon in the Indo-Gangetic plains during winter also need to be addressed, says Kuttippurath. A component of fine particulate matter, black carbon has been linked to heart disease and respiratory problems and research suggests that long-term exposure increases mortality rates.

“These findings highlight the importance of continued investment in technology and regulation to improve air quality in the Indo-Gangetic Plain,” says Kuttippurath.

The Indo-Gangetic plain has become the global hotspot for air pollution, with nine of the world’s ten most polluted cities falling in the region. Earlier this month (3 November), areas around Lahore recorded unusually high levels of pollution, with the AQI meters scoring an unprecedented 1,900 against the hazard level of 300.

According to a World Bank report, nine out of the world’s ten cities with the worst air pollution are in South Asia, where dirty air leads to an estimated two million premature deaths each year along with major economic losses. Here, several cities have concentrations of PM 2.5 that are 20 times higher than what the WHO considers healthy at five micrograms per cubic metre, the report says.

Apart from emission sources common around the world, there are activities specific to South Asia that contribute large amounts of PM 2.5 to ambient air, according to the World Bank analysis. At any given location, PM 2.5 in ambient air originates from a wide range of upwind sources extending over several hundred kilometres, the report says.

Independent circular economy expert Swati Singh Sambyal says that cutting emissions is an urgent health priority. “Reducing emissions through cleaner energy, stricter pollution controls, and circular sustainable practices such as decentralised waste management systems can break the cycle of seasonal smog that disrupts lives and fills hospitals,” he tells SciDev.Net.

During periods of temperature inversion, also known as thermal inversion, emissions from vehicles, industries, and crop burning have nowhere to disperse, creating thick, hazardous smog, impacting millions of people, says Sambyal.

“As thermal inversion seasons intensify, coordinated efforts to lower emissions are essential for clearer skies and healthier communities in both Pakistan and India,” he adds.

This piece was produced by SciDev.Net’s Asia & Pacific desk.