CNN  — 

When India imposed a nationwide lockdown a week ago, it was designed to stop the imminent spread of the novel coronavirus.

But grinding this country of 1.3 billion people to a near halt has also provided a temporary remedy to another pressing health issue: suffocating pollution levels.

The world’s largest lockdown means all factories, markets, shops, and places of worship are now closed, most public transport suspended and construction work halted, as India asks its citizens to stay home and practice social distancing. So far, India has more than 1,300 confirmed cases of Covid-19, including 35 deaths.

Already, data shows that the main cities are recording much lower levels of harmful microscopic particulate matter known as PM 2.5, and of nitrogen dioxide, which is released by vehicles and power plants.

PM 2.5, which is smaller than 2.5 micrometers in diameter, is considered particularly dangerous as it can lodge deep into the lungs and pass into other organs and the bloodstream, causing serious health risks.

The sudden fall in pollutants and the subsequent blue skies signal a dramatic shift for India – which has 21 of the world’s 30 most polluted cities, according to the IQAir AirVisual’s 2019 World Air Quality Report.

In the capital, New Delhi, government data shows the average concentration of PM 2.5 plunged by 71% in the space of a week – falling from 91 microgram per cubic meter on March 20, to 26 on March 27, after the lockdown began. The World Health Organization considers anything above 25 to be unsafe.

The data from the Central Pollution Control Board (CPCB), part of India’s Environment Ministry, was collated by the Centre for Research on Energy and Clean Air (CREA).

Nitrogen dioxide went from 52 per cubic meter to 15 in the same period – also a 71% fall. Mumbai, Chennai, Kolkata and Bangalore have also recorded a fall in these air pollutants.

“I have not seen such blue skies in Delhi for the past 10 years,” said Jyoti Pande Lavakare, the co-founder of Indian environmental organization Care for Air, and author of upcoming book “Breathing Here is Injurious To Your Health.”

“It is a silver lining in terms of this awful crisis that we can step outside and breathe.”

Lowest traffic pollution

Even before the national lockdown started on March 25, the phased shutdowns in India were having an impact.

During the first three weeks of March, the average nitrogen dioxide levels declined by 40-50% in the cities of Mumbai, Pune and Ahmedabad, compared with the same period in 2018 and 2019, said Gufran Beig, a scientist with the System of Air Quality and Weather Forecasting And Research (SAFAR) under India’s Ministry of Earth Sciences.

“The reduced fossil fuel emissions due to (the) transport sector and slowdown in other emissions-related activity is slowly reducing the air pollutants,” Beig said.

The nationwide curfew in India on March 22 also resulted in the lowest one-day traffic pollution levels on record, analysis from CREA said. Other dangerous pollutants, PM2.5 and the larger PM10, which are less than 10 micrometers in diameter, also dropped steeply, the report added.

“It is most likely that even the record of March 22 will be broken, and we are seeing more and more cleaner days as industries, transportation and energy generation and demand are reducing across the country,” said Sunil Dahiya, an analyst based in New Delhi for CREA.

Similar patterns showing drastic falls in pollution levels were seen in parts of Europe and China since their lockdowns, as industry and transport networks grind to a virtual halt.

But this data is no reason to celebrate, Dahiya said.