New study calls for action on air pollution in Northern India

New research led by the University of Leicester calls for urgent action on open field burning to reduce the intensity of post-monsoon air pollution in Northern India.

Experts from the UK and India combined over a decade of satellite measurements with air quality modelling to better understand factors controlling the severity of the poor air quality episodes, particularly across the highly-populated Indo-Gangetic Plain.

The resulting study carefully considered the possibility of whether delays in farmers harvesting rice paddy, driven by government policy aimed at preserving groundwater reserves, were unexpectedly responsible for worsening the air quality. 

Dr Sembhi and colleagues found that the consequences of the government’s ‘delaying’ policy on crop residue burning actually had a minimal effect on worsening the air quality, which instead was mostly controlled by the sheer amount of residue being burnt in open fields as well as the local weather conditions at the time of the fires. 

Dr Harjinder Sembhi from the School of Physics and Astronomy at the University of Leicester explains: “Each October, farmers in northwest India clear their fields of millions of tonnes of unwanted straw following harvesting of rice. As fields need to be cleared rapidly to make way for the winter wheat growing season, farmers feel they have very few affordable options other than to burn the rice residue. 

“Smoke from this rice residue burning is a major source of hazardous fine particulate matter, which can be transported over very long distances to affect hundreds of millions of citizens, especially in Delhi where local pollution sources can already affect air quality.

“Our results demonstrate that the delays in residue burning observed so far do not necessarily drive up pollution. Rather the local weather conditions and simply the amount of material being burned both play a key role when it comes to the accumulation of pollutants that then affects the quality of the air people breathe, even hundreds of kilometres away from the fires themselves.”

The study makes a strong case to support farmers with affordable and sustainable alternatives to burning, so that they can efficiently and safely manage large amounts of rice residue and avoid needing to set fire to the material in the open air.

Study co-author, Professor SN Tripathi from the Indian Institute of Technology in Kanpur, is on the steering committee of the Government of India’s National Clean Air Mission and adds: “The findings of this study will help better management of crop residue, to minimise its impact on air quality, which is aligned with the effective control measures being implemented through the National Clean Air Mission. It is encouraging to see already that there are have been some reductions in crop residue burning.”

Professor Martin Wooster from NCEO and the Leverhulme Centre for Wildfires, Environment and Society at King’s College London, comments: “Our results confirm that rather than focusing on the exact timing of the fires, it is the Government-led efforts to provide farmers alternative means for crop residue management that are crucial to improving the region’s air quality and thus the health of Indian citizens.”

Another co-author Professor Hartmut Boesch from the School of Physics and Astronomy, University of Leicester and NCEO, UK, says: “This study is a great example of how we can use satellite observations not only to gain new scientific insights into the impact of crop residue burning on air quality and human health, but also to provide material evidence that can underpin government policies and help determine their effectiveness.”