The second phase of the odd-even scheme — implemented to improve Delhi’s air quality — saw a rise in pollution levels compared to the period just before it was in force, monitoring by The Energy and Resources Institute revealed.
Another study by IndiaSpend, a portal that runs a network of ‘low cost sensors’ across the Capital, said the increase was nearly 23% compared to the first fortnight of April. The scheme’s second round was enforced from April 15 to April 30.
Experts, however, said the odd-even road rationing scheme wasn’t to be blamed for the foul air quality. Wind speed and summer winds pushing emissions from neighbouring states into Delhi were responsible. In summer, low wind speed increases pollution and high winds makes the air cleaner.
Teri’s Sumit Sharma who led the monitoring team said that on Saturday, the last day of the scheme, the 24-hourly pollutant concentrations were the highest at many stations.
“On an average of all stations considered in Delhi and NCR, the PM2.5 concentrations were about 54% higher during the odd-even scheme period, in comparison to the week before,” said Sharma.
He, however, said the increase was mainly due to much lower wind speeds during the odd-even weeks. “The quantified impact of odd-even scheme is yet to be evaluated,” he said.
Teri had collected daily data from four Delhi Pollution Control Committee monitoring stations. The environment policy research body also monitored five locations on its own.
The study by IndiaSpend, based its findings on the volume of fine respirable pollutants PM 2.5 and PM 10, not taking into account gaseous pollutants such as ozone which is being monitored by few agencies.
The report said the average PM 2.5 and PM 10 concentrations in the city’s air were 68.98 and 134.39 micrograms per cubic metre (ug/m3) between April 15 and 29 indicating moderate conditions. The concentrations were 56.17 ug/m3 and 110.04 ug/m3 during the first 15 days of the month.
The report, based on hourly averages, noted that pollution was the worst at 7 am every day, in line with experts’ explanation that early morning hours are more polluted as pollutants build up through the night due to favourable weather conditions and truck traffic.
“5pm was the best hour for Delhi during the odd-even phase, with PM 2.5 levels at 21 ug/m3, indicating ‘good’ air quality,” it said.
The Central Pollution Control Board on April 21, during a hearing at National Green Tribunal, said there is no data to suggest that the odd-even scheme brought down vehicular pollution in Delhi.
The Delhi Pollution Control Committee, however, has been claiming pollution levels went down. Its data collected from mobile vans stationed at spots across Delhi, PM 2.5 and PM 10 levels were within permissible limits in most areas.
A study by School of Planning and Architecture had showed that the share of private vehicles in the city rose by almost 50% during odd-even phase two.