The nationwide lockdown , and halting of most economic activities as a way to combat the novel coronavirus ( COVID-19 ) has brought about significant improvements in air quality across the country, albeit in the short term.
However, this phase of good air quality is lending itself as a real-life experiment to determine the lowest achievable pollution levels possible in a very long time. Attaining blue skies in a short period of about two weeks has allowed us to take a long view of the problem, the multiple sources of air pollution and to imagine a future with clean air. It has allowed us to understand clearly which solutions will work, how, and at what scale.
Fall in pollutant levels
Central Pollution Control Board data analysed from the last two weeks indicates a sudden reduction in pollutant levels across the country, including in some of the most polluted cities. Due to stringent travel restrictions, shutting of most industries and halting commercial and construction activity, the impact of air quality improvements has become immediately visible within and outside the cities.
Delhi, across its 35 monitoring locations, has recorded a drop of 44% in PM2.5 levels between March 24 and April 6. Noida and Gurugram have recorded similarly large and rapid decreases of 51% in their PM2.5 levels and 55% in PM10 levels. Other capital cities, such as Mumbai, Bengaluru and Lucknow have reported a decrease in the range of 18% to 30% during the lockdown period.
It is also notable that the decrease in particulate levels is the same if we compare the two week period (March 24 to April 6) between 2019 and 2020. Delhi NCR registers a drastic decline of 65%-70% in PM10 values compared with 2019 mainly due to construction activity coming to a grinding halt.
Also, Delhi, Mumbai, Bengaluru and Kolkata, and even smaller cities such as Jaipur and Guwahati, have recorded significant drop in nitrogen dioxide (NO2) concentration, ranging from 53-68%, which is largely related to a dramatic decline in vehicle movement. Mumbai, with the maximum COVID-19 hotspots , stands out with a 68% drop in NOX during the two week lockdown period in which data has been collected. Compared to last year, Kanpur has registered a drop of 83% in NOX pointing to most vehicles going off the road during the lockdown.
Sulphur dioxide, another polluting gas, mostly released by burning of coal, oil and gas, either in vehicles or in power plants and other industries, also registered a big drop. In Pune, SO2 level was 44% less during the lockdown, as compared to the week before. For the same time, readings in Ahmedabad, Mumbai, Hyderabad and Kolkata were roughly a quarter less, coinciding with reduced industrial activity and transport emissions.
Major sources
The National Clean Air Programme aims for an improvement of 20%-30% in the air quality by 2024, taking 2017 as the base year. It is necessary to address all major sources including transport, industry, residential, waste burning, road dust, agriculture residue burning, and construction, if air quality across large swathes of India has to be restored to moderate levels.
Our initial findings based on real-time source apportionment of online PM2.5 composition measurements in Delhi, over the period of lockdown show that contribution from incinerators has dropped, indicating much less processing of hotel and food waste. The real time analysis also shows contribution from tyre wear on road dropping close to insignificant. This points to the urgent need for guidelines on reuse of tyres.
Urgent retrofitting of flue gas desulphurisation units in thermal power plants is necessary as thermal plants are likely to continue in the near future. Going forward, tackling the auto sector is crucial. In bringing the economy back to life, filling the gap with an electric vehicle-specific stimulus package could be an interim solution to improving air quality.
Waste disposal and crop residue
The link between waste disposal in cities and poor air quality is a conspicuous one, which deserves due attention and action. Solutions lie in efficient waste segregation at source followed by recycling — especially for industrial units.
It is evident that a large amount of crop residue after each harvest cycle cannot be managed through traditional means or mechanised harvesters alone. Focus on innovation in crop residue management to minimise stubble burning in a sustainable and effective way across different locations alone can control this issue.
As the government prepares the largest ever recovery package to place the economy back on track, undertaking reforms such that it brings in less polluting industries, more clean transport and more resilient infrastructure will ensure that India is able to lock in a clean future and is better prepared for any shocks in the future.
(The author is a professor at IIT-Kanpur and member of the Steering Committee, NCAP MoEFCC)
