he Delhi government's claim that pollution in the Capital has reduced over the past week is at odds with data of the daily average levels as well as peak values of particulate matter (PM).

As per a report submitted by the government to the High Court on Friday, the peak levels of PM showed a decrease from January 1, when the odd-even experiment began. The report, compiled by the Environment Pollution Control Authority (EPCA), says that peak pollution recorded during the odd-even experiment has been the lowest compared to those in earlier smog episodes this winter. A smog episode is when pollution levels are “severe” as per the National Air Quality Index (NAQI) for several consecutive days.

However, data obtained from the NAQI portal tells a different story. AQI values for PM2.5 were obtained across eight monitoring stations in Delhi for which adequate data was available. Analysing this data, The Hindu found that there are no declining trends in air pollution. The air quality has been steadily deteriorating from December 25, 2015, with occasional dips, which are no better than pollution in the week before.

According to the Centre for Science and Environment (CSE), which carried out an analysis of peak levels for the EPCA report, the odd-even policy has had an impact despite hostile weather conditions.

“This past week, when the weather has been more hostile than in November and December, the peak levels have been less in comparison. Though, average pollution levels have increased,” said AnumitaRoychowdhury, the head of CSE's clean air campaign.

She added that the peak levels had decreased in the week since the experiment began, despite wind speed being almost nil. “This is just opposite of what should have happened,” she said.

As per the CSE analysis, PM2.5 levels decreased on January 1,4 and 5 when wind speed also fell. As opposed to the case on December 30 and 31, when the level of PM2.5 shot up as wind speed decreased.

But, this is in contradiction with The Hindu’s analysis, where we found that peak value during odd-even scheme is either comparable or just slightly lower to peaks observed from the beginning of December.

Ms. Roychowdhury said it is unfair to judge the odd-even scheme “like a usual initiative”.

“Delhi has never carried out an emergency action like this. Those who are trying to kill the action should know that when the odd-even experiment ends, congestion will come back, and the pollution levels will be higher,” she said.

Meanwhile, EPCA chairperson Bhure Lal said the government should be allowed to continue the programme. “The odd-even policy is having an impact, but it is not that visible because of the weather conditions,” said Mr. Bhure Lal. The future of the experiment will be decided on January 11, when the High Court gives its order.

Those who are trying to kill it should know that when the odd-even experiment ends, congestion will come back, and pollution levels will be higher

AnumitaRoychowdhuryHead of CSE’s clean air campaign

Data analysis shows no declining trends in pollution, and that air quality has been steadily deteriorating