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The Smog Choking this Indian City is Visible from Space

Seasonal fires and a slew of air pollutants are obscuring skies across northern India, registering “very unhealthy” air quality in New Delhi and causing schools to shut down. Advisories recommend residents avoid spending time outside in the city, which has experienced toxic smog from around the beginning of November.

“The smoke has gone all over to the Bay of Bengal,” said Hiren Jethva, an aerosol scientist at Morgan State University and NASA. So far, the fire activity is lagging behind other years, but he said “this many fires are still sufficient to create the air quality issue in the vicinity of the burning region.”

The thick plume of smoke pollution, sprawled across northern India, was visible on NASA satellite imagery.

The air quality index in New Delhi for PM2.5 — a particularly hazardous pollutant known as particulate matter 2.5 — reached 285 or “very unhealthy” on Thursday, which is the second most severe level, according to data from the U.S. Embassy. These tiny pollutants, spanning one-thirtieth of the width of a human hair, can travel into our lungs and bloodstream to cause heart disease or lung cancer.

This dip in air quality, especially around New Delhi, occurs every year in the months ahead of winter. Every November, farmers in northwestern India burn off excess paddy straw after rice harvest to clear the land for the next crop — a practice known as stubble burning. The smoke spreads across the region, including the country’s biggest city New Delhi, which is home to almost 35 million people.

The level of smoke pollution is due to “farm fires in the northwest, particularly two states in Punjab and Haryana,” said Jethva, although he said fire activity in Haryana is less this year. “It happens every year.”

The crop fires add to a mix of other hazardous pollution sources in the area, including vehicles, industrial activities and fires for heating and cooking. Dust coming from the Thar Desert to the west can also pollute skies.

Given the pollution levels, people with heart or lung disease as well as older adults and children should avoid outdoor activities. Air quality has deteriorated since the beginning of November.

The hazardous air quality has forced school closings around the region and in Pakistan, which has also experienced elevated air pollution. Local governments have dismissed schools and extended the upcoming winter break, while some have opted for virtual learning.

This year, the burning season peak appears to be occurring later, said Jethva. Stubble burning typically takes place during 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 monsoon rains arrived later, so farmers pushed back their rice harvest and subsequently their burning season.

Jethva expects burning season to last for another week or so, but the delay could spell more trouble as the Hindu festival of Diwali, celebrated with fireworks, approaches. The air pollution from the crop fires and celebratory fireworks could continue or further deteriorate air quality. Jethva said burning season and Diwali lined up in 2016, which now ranks as the worst burning season in the past two decades of satellite data.

“If we haven’t seen the peak yet of the biomass burning, then maybe it will peak in the next two or three days,” said Jethva. “If it coincides with the Diwali fireworks, that is going to be a huge problem facing the big cities.”

Officials in New Delhi are trying to find ways to mitigate the poor air quality. After Diwali, local authorities will instate the “odd-even” vehicle rule, where only certain vehicles will be allowed on the road on certain days, to reduce pollution from tailpipes.

Scientists will also attempt to wash out some of the pollution in the city by inducing rain, Reuters has reported. Around Nov. 20, scientists leading the trial from the Indian Institute of Technology at Kanpur will spray overhead clouds with salts to trigger heavy rains. Cloud seeding has faced skepticism and criticism, but the technology has been used across the world, from the western United States to the Beijing Olympics.

“We have to see what happens in the next couple of weeks, whether [smoke] remains in the peak and then it goes down. Eventually it will,” said Jethva.

Source : Washington Post