Dangerously high levels of air pollution in New Delhi during the fall and winter months are largely the result of post-harvest burning of crop residue, according to a new study in the journal Nature Sustainability. Pollution levels from crop burning are so high they rival fossil fuel emissions during peak summer months.

New Delhi has long struggled with the worst air quality of any major city in the world, according to World Health Organization data. Last month, the megacity experienced air pollution levels 12 times United States government-recommended levels. Air pollution in India kills an estimated 1.5 million people every year, and a recent study in the journal GeoHealth found that nearly half of these deaths occur in the Indo Gangetic Plain, the northernmost part of the country that includes New Delhi.

Crop residue, such as roots and stems, is often burned to help prepare the field for seeding the next season. Burning this agricultural waste, however, also releases black carbon, a type of fine particulate matter formed from incomplete combustion. These particles are then funneled by air currents from rural farms to New Delhi, traveling from as far as 125 miles.

Read more at Yale Environment 360

Photo Credit: CIAT via Wikimedia Commons