When I saw reports that Indian cities had seen major improvements in air pollution amid the covid-19 lockdown, I WhatsApped my family members in New Delhi to ask about their experience. Did it seem like the air was cleaner?
“Certainly. Since there are no vehicles on the road,” my uncle responded.
“There is a massive difference!!” my cousin chimed in. A couple of others agreed.
Amid concerns about the coronavirus pandemic, many offices, factories and shops, and airports shutdown over the past two weeks. Cars stayed in their parking spots. On March 22, the federal government called for a one-day curfew, for which each state was asked to do what it could to encourage citizens to stay in their homes from 7 a.m. to 9 p.m. And three days later the federal government called for a nationwide 21-day shutdown of nearly all services.
India is home to 21 of the world’s 30 most polluted cities, but the nation’s air has been cleaner in recent weeks. Experts at the Center for Research on Energy and Clean Air (CREA) found the single-day curfew resulted in the lowest average level of nitrogen dioxide pollution ever recorded in India’s urban areas during springtime. In the nation’s capital of New Delhi, where most of my family lives, average concentrations of a common form of particulate matter known as PM 2.5 dropped from 91 micrograms per cubic meter on March 20 to 26 micrograms on March 27—a 71 percent difference—according to data from the CREA and Energy and India’s Central Pollution Control Board shared with CNN. The World Health Organization considers levels under 25 to be safe. Mumbai, Chennai, Kolkata, and Bangalore also saw a drop in these air pollutants as well.
Other data show a similar pattern at work. New Delhi’s Air Quality Index—a measure based on concentrations of particulate matter, ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide emissions—has also improved dramatically, according to the Environmental Protection Agency’s AirNow database. Mumbai’s concentrations of pollutants have also dropped since social distancing measures began.
To be clear, this reduction in emissions doesn’t mean India is doing well right now. Dozens of people in India have died of covid-19. And for the millions of people who rely on informal labor sectors throughout the country, the lockdown is having devastating effects, too. Plus, it’s not exactly clear how much this reduction in emissions is due to social distancing measures.
“It is true that pollution levels are going down and will continue to be lower as a result of lockdown,” Pawan Gupta, Senior Scientist at the Earth Sciences of Universities Space Research Association at NASA’s Marshall Space Flight Center, told Earther in an email.
The lockdown certainly could be playing a role. But there are other factors that influence air pollution levels, too. Over the past several days, western and northern India have seen heavy rains, which can also cause air pollution levels to drop.
“Rain is a very effective aerosol removal process from the atmosphere and can bring down particulate matter values,” Gupta said.
While having people shelter in place is likely reducing air pollution tied with travel and industry, another factor may be increasing emissions. Residents often burn agricultural residues, fuel wood, and dung for energy, all of which contribute to air pollution. Gupta pointed to eastern and southern India as places where burning biomass could be offsetting some of the air pollution improvements tied to the lockdown.
Though the exact effects are hard to quantify, Gupta expects the decrease in pollution will continue: India’s stay-at-home order goes on for another two weeks. That kind of order is unprecedented for the nation.
“The current lockdown in India (and elsewhere in the world) is a natural experiment and something like this never happened in our lifetime,” said Gupta.
As a result of these measures, “pollution levels will go down, no doubt about it,” he said. But the more important question is how large that effect will be—and if its possible to keep them lower when we’re not facing a pandemic and harsh social distancing measures.