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Seasonal fires and a slew of air pollutants are blanketing the skies over northern India, causing “very unhealthy” air quality in New Delhi and forcing schools to close. The advisories advise residents not to spend time outdoors in the city, which has been experiencing toxic smog since around early November.
“The smoke has spread to the Bay of Bengal,” said Hiren Jethva, an aerosol scientist at Morgan State University and NASA. So far, fire activity is lagging behind other years, but he said, “This number of fires is still enough to cause the air quality problem near the burning region.”
The thick cloud of smoke spreading across northern India was visible in NASA satellite images.
New Delhi’s air quality index for PM2.5 – a particularly dangerous pollutant called particulate matter 2.5 – reached 285, or “very unhealthy,” on Thursday, the second-highest level, according to U.S. Embassy data. These tiny pollutants, which are one-thirtieth the width of a human hair, can enter our lungs and bloodstream and cause heart disease or lung cancer.
This decline in air quality, particularly around New Delhi, occurs every year in the months leading up to winter. Every November, farmers in northwest India burn excess rice straw after the rice harvest to clear the land for the next crop – a practice known as stubble burning. The smoke is spreading across the entire region, including the country’s largest city, New Delhi, which is home to nearly 35 million people.
The extent of smoke pollution was due to “farm fires in the northwest, particularly in two states in Punjab and Haryana,” Jethva said, although he said fire activity in Haryana was lower this year. “This happens every year.”
The crop fires add to a mix of other dangerous sources of pollution in the region, including vehicles, industrial activities and fires for heating and cooking. Dust coming from the Thar Desert in the west can also pollute the sky.
Given the pollution, people with heart or lung disease, older adults and children should avoid outdoor activities. Air quality has deteriorated since the beginning of November.
The dangerous air quality has led to school closures in the region and in Pakistan, which is also experiencing increased air pollution. Local governments have closed schools and extended the upcoming winter holidays, while some have opted for virtual learning.
This year, the peak of fire season appears to come later, Jethva said. Stubble burning typically occurs in the last week of October and first week of November, but NASA satellite data showed fire activity was unusually quiet in late October. One reason could be that the monsoon rains came later and farmers postponed their rice harvest and thus the burning season.
Jethva expects the fire season to continue for about another week, but the delay could spell more trouble as the Hindu festival of Diwali, celebrated with fireworks, approaches. Air pollution from the crop fires and festival fireworks could continue or further deteriorate air quality. Jethva said the fire season and Diwali occurred in 2016, which is now considered the worst fire season in the last two decades, according to satellite data.
“If we haven’t seen the peak of biomass burning yet, maybe it will peak in the next two or three days,” Jethva said. “If it coincides with Diwali fireworks, it will be a huge problem for major cities.”
Officials in New Delhi are trying to find ways to mitigate poor air quality. After Diwali, local authorities will introduce the odd-even vehicle rule under which only certain vehicles will be allowed on the road on certain days to reduce pollution from exhaust pipes.
According to Portal, scientists will also try to use rain to wash out some of the city’s pollution. Around November 20, scientists at the Indian Institute of Technology in Kanpur, who are leading the experiment, will spray the clouds overhead with salts to trigger heavy rains. Cloud seeding was met with skepticism and criticism, but the technology has been used around the world, from the western United States to the Beijing Olympics.
“We’ll have to see what happens in the next few weeks [smoke] stays at the peak and then it goes down. It will be like this at some point,” Jethva said.