Pollutants reduced by 18 per cent on odd-even days, claims report

A new study has claimed that the volume of respirable pollutants in the air were reduced by up to 18 per cent during 15-day trial of the odd-even scheme that regulated the plying of four-wheelers on the national capital’s roads.

A US-based study said that while absolute pollution levels increased across the National Capital Region (NCR) in January as compared to the previous month, the levels in Delhi saw a smaller increase owing to the pilot licence plate policy.

Jointly conducted by researchers at the Energy Policy Institute at the University of Chicago (EPIC) and Evidence for Policy Design group at Harvard University, the study found stark reductions in pollutants around the noon hours from January 1 to 15.

The study revealed that the impact was much “higher” during the hours when the scheme was in force as the gap between Delhi’s pollution and the neighbouring regions widened steadily until at least midnight.

The study has based its findings on the Central Pollution Control Board and private portal IndiaSpend data. “Particulates (PM 2.5) declined by 10-13 per cent on an average (i.e. overall 24 hours) and by 18 per cent on average during the period when the scheme was in force (i.e. between 8 am to 8 pm). After 8 pm, there was (as expected) no effect, which is why the average for overall 24 hours is lower than the average of daytime,” said EPIC-India director Anant Sudarshan.

PM 2.5, the tiniest and deadliest of all respirable pollutants, measures around 2.5 microns enabling it to embed deep into the lungs and subsequently enter the bloodstream. Its safe limit is 60 ug/m3 as per Indian standards.

The study’s conclusion was arrived at by comparing Delhi’s pollution figures with that of Faridabad, Gurgaon and Noida, where the scheme was not enforced, as the NCR region has very similar weather conditions and are equally exposed to external factors affecting such as crop burning in the nearby states.

Under the scheme, the cars with odd and even number registration plates plied on alternate days for the first 15 days of the year. The Delhi government is likely to roll out its second phase in March-April, after the completion of the board exams.

Researchers explained that reducing half the cars could make so much difference despite them accounting for a fraction of overall pollution chiefly in two key ways. The researchers, Mr Sudarshan, Santosh Harish and Michael Greenstone at Chicago University and Rohini Pande at Harvard University, measured the impact of the programme on PM 2.5 concentrations using a difference-in-differences statistical approach.