[NEW DELHI] India’s capital should turn its attention to tackling emissions on its own roads to curb air pollution, rather than blaming crop burning in neighbouring states, say researchers.

In 2019, 1.67 million deaths in India were attributable to air pollution, which is linked to numerous diseases including lung cancer, pneumonia and heart disease.

In New Delhi, the crisis is clear to see. Every winter the city becomes enshrouded in smog as multiple sources dirty its air, making it one of the world’s most polluted cities.

Fine particulate matter emitted by the millions of vehicles that take to the city’s roads every day, smoke emitted by its industries, dust emanating from the booming construction sector, and the burning of agricultural residues in neighbouring states of Punjab and Haryana, all contribute to Delhi’s woes.

However, crop residue burning, which has been the focus of policies to curb air pollution in the capital, actually contributes less than expected, a study has found.

By analysing sensor data from 30 different locations across Delhi, Punjab and Haryana, and taking into consideration various meteorological factors, researchers concluded that the emissions from stubble burning in Punjab and Haryana contributed about 14 per cent of Delhi’s pollutants.

Previous studies had estimated that stubble burning was responsible for up to 40 per cent of pollutant concentration in Delhi, which formed the basis of the policies aimed at mitigating air pollution in the capital.

Delhi’s air pollution mitigation policy has probably “over relied” on the reduction of crop burning emissions, the study said.

Researchers found that stubble burning in Punjab and Haryana has gone down significantly. Between 2015-2016 and 2022-2023, fire incidents decreased by about 49 per cent and 72 per cent in Punjab and Haryana respectively. However, during the same period, Delhi continued to reel under severe air pollution every winter.

“Our study reveals that the sustained level of pollutant concentration in Delhi-National Capital Region is decoupled from crop residue burning in the neighbouring states,” says Poonam Mangaraj, postdoctoral researcher at the Research Institute for Humanity and Nature, in Kyoto, Japan, who participated in the study.

“The implication is that Delhi and its immediate neighbourhood have to take steps to control their own emissions now.”

Mangaraj admits that on some days emissions from stubble burning can be significant. “On a bad day, winds blowing in from Punjab can transport a large amount of fine particulate matter and exacerbate the situation in Delhi,” she says.

However, recognising the limited role of stubble burning activities could drive policy in new directions, according to air quality experts.

“This new insight helps formulate more effective air quality policies by enabling targeted, evidence-based interventions,” says Suresh Ramasubramanya Iyer, an air quality specialist at The Energy and Resources Institute, New Delhi.

“This nuanced understanding highlights the need to focus on dominant urban sources like vehicular emissions, construction dust, and industrial activities, which significantly affect Delhi’s air quality year-round,” says Iyer, who didn’t participate in the study.

Over the years, the transportation sector has emerged as the single biggest contributor to Delhi’s air pollution.

“About 28 per cent of fine particulate matter concentration is contributed by the vehicle emissions,” says Iyer, quoting a study conducted by TERI in 2019.

This is despite the fact that Delhi has more than 350 km of metro and more than 7,000 buses that run on Compressed Natural Gas (CNG). It has also banned diesel vehicles that are more than ten years old and petrol vehicles that are more than 15 years old.

However, counteracting these measures is an explosion in the number of vehicles. According to the Delhi Economic Survey 2022-23, Delhi had almost 8 million vehicles in 2021-22, including more than 5 million two wheelers, and 2 million private cars or jeeps.

“The sheer volume of vehicles, even with cleaner technologies, leads to significant cumulative emissions,” says Iyer.

“The dominance of two-wheelers, which emit higher pollutants per unit of fuel compared to buses or cars, adds to this burden.”

The rapid rise in the number of vehicles on Delhi’s roads and the resulting emissions call for serious interventions from the government, specialists say.

A multi-pronged approach is needed to reduce vehicular pollution, according to Iyer.

“Metro and CNG bus networks are commendable, but they do not fully address the needs of a rapidly growing population, leaving many areas underserved by public transport,” he says.

“Expanding and improving public transport, including metro and bus networks, is essential, alongside promoting non-motorized transport and enhancing last-mile connectivity.”

Mangaraj observes that controlling air pollution is not easy, but many cities have been successful.

She adds: “Cities like London, Los Angeles, and Tokyo have tackled the issue of air pollution. These cities committed to drastic changes, and Delhi has to follow suit.”

SciDev.Net contacted India’s Department of Transport for comment but received no response ahead of publication.

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