After another winter marred by soaring air pollution levels, India's government has announced new measures to help tackle the problem in the country's northern regions.
Many experts have highlighted crop burning in the northern states of Punjab and Haryana as a key cause of the pollution crisis, leading India's finance minister Arun Jaitley to use the budget, announced Thursday, to present a new subsidy for farmers aimed at curbing the practice.
Every winter, farmers in northern India burn the stubble left over after the autumn harvest in order to quickly and cheaply clear the fields in time for the next planting.
This results in Delhi, the nation's capital, and surrounding regions being overrun by a thick haze of pollution.
While the burning lasts just a few weeks, it has a significant impact, experts say.
Delhi's air quality could improve by 90% if crop burning is eliminated, according to a 2016 study by the Indian Institute of Technology, Kanpur.
"I think it's a crucial measure," said Chandra Venkataraman, professor of chemical engineering at the Indian Institute of Technology Bombay. "For a large number of the northern states, agricultural residue burning is the second most important source contributing to air pollution."
In recent years, crop burning has become a political issue.
In November 2017, the capital choked on excessive pollution. Air quality readings reached frightening levels, at one point topping the 1,000 mark on the US Embassy's air quality index. The World Health Organization considers anything above 25 to be unsafe.
That measure is based on the concentration of fine particulate matter, or PM2.5, per cubic meter. The microscopic particles, which are smaller than 2.5 micrometers in diameter, are considered particularly harmful because they are small enough to lodge deep in the lungs and pass into other organs, causing serious health risks.
At the time, the issue devolved into a political back-and-forth between Delhi's chief minister and the chief minister of Punjab and Haryana.
The solution now being offered is a subsidy for a range of machines that should remove the need for a farmer to set fire to his field. For example, one machine allows a farmer to plant seeds without having to clear his field first by tilling the soil as it plants -- preventing clogs caused by leftover rice crops.
A national and multi-factoral problem
While Delhi attracts the most attention for its intense air pollution, experts say it's a nationwide problem.
No Indian city met the World Health Organization's healthy air quality standard in 2015 or 2016, found a report by Greenpeace released Monday. The report gathered data from 280 cities across the country.
"Somehow the budget seemed to have treated the air pollution as a Delhi-NCR problem," said Anumita Roy Chowdhury Executive Director of Research and Advocacy at the Centre for Science and Environment.
"They're not considering it through a national dimension, the national scale of the air pollution crisis."
The problem is also not limited to urban areas.
Rural and urban India have roughly similar levels of exposure to air pollution, according to a comprehensive study released in January by an international team of scientists, including experts from the Indian Institute of Technology Bombay and the Health Effects Institute in the US.
The study also found that the biggest source of air pollution was residential biomass burning by individuals, in other words, people burning cow dung, wood, or other materials for heating or cooking. The second was the usage of coal, mainly by industries. Crop burning was the fourth largest source and accounted for about 6% of the pollution to which people were exposed.
While crop burning is important, the government needs to focus on these major sources of pollution as well, specifically coal use and biomass burning, said E. Somanathan, an economics professor at the Indian Statistical Institute.
"The thing about air pollution is that it adds up," he said. "It doesn't make any sense that we will tackle this, but not the other. You have to tackle all the other sources. You have to act on all fronts."