By Sayantan Ghosh
Diwali 2019 was no different compared to past years for Delhi as the Air Quality Index (AQI) dipped to ‘severe’ levels the day after the festivities. The spike in pollution wasn’t surprising, and residents are now familiar with the situation. As the air grew more toxic, the Delhi government shut down schools and the Supreme Court-appointed Environment Pollution (Prevention & Control) Authority declared an emergency situation in the capital while directing the closure of all construction activities. And, the Aam Aadmi Party (AAP) government also ordered the odd-even car-rationing drive to combat the pollution.
The success of the scheme, which restricts private cars from driving on alternate days based on the last digit on their number plates, has proved that even the most severe environmental problem can be fought with political will and people’s participation. The system was piloted by Delhi in January 2016, becoming the first state to bring such a stringent anti-pollution emergency measure in India. The success of the scheme also brought for it the approval of the EPCA and it is now part of the Graded Response Action Plan (GRAP), an emergency mechanism to combat pollution. GRAP suggests that if the AQI reaches the emergency (severe-plus) level, then the odd-even drive should be implemented.
Another paper, by researchers from Harvard University and the University of Chicago (Michael Greenstone, Rohini Pande, Santosh Harish, Anant Sudarshan) uses government monitoring data, and a statistical technique called difference-in-differences. The analysis compares Delhi’s monitors to monitors from neighbouring cities in the national capital region (NCR) using PM2.5 data before, during, and after the two pilot rounds in January and April 2016. The assessment technique assumes that air quality changes in similar ways within and outside Delhi due to meteorology and other factors that are common to both. This second analysis finds that PM2.5 levels were lower by 14-16 per cent on average between 8am and 8pm during the odd-even scheme in January 2016. No impact was detected at night. No impact was detected when the programme was repeated in April.