Confusion about the impact of the odd-even restriction on Delhi’s air persisted on Friday as the Delhi government claimed that peak pollution levels had touched an all-time low while independent experts claimed that pollution had risen sharply during the first week of the restriction.
While Delhi Dialogue Commission vice chairperson Ashish Khetan, quoting the Environment Pollution Control Authority (EPCA) report said that peak pollution levels in the city were at a historic low.
EPCA based its findings on the Delhi Pollution Control Committee (DPCC) and the Centre for Science and Environment (CSE) data. Peak levels of November, December and January were 606, 524 and 391 micrograms per cubic metre respectively, it said.
IndiaSpend, a news portal that has set up air quality monitoring stations at Sarvodaya Enclave, India Habitat Centre, Munirka, Nizamuddin East, Connaught Place and Chanakyapuri, however, claimed that air-pollution levels in terms of PM 2.5 levels in Delhi rose 50% during the first week of the odd-even restriction.
The report does take into consideration factors such as temperature, wind speed and humidity and says this could be behind the increase.
“The increase in PM 2.5 level indicates the need to understand deeper the impact of policy changes, such as the odd-even measure, on Delhi’s air. Additional factors, such as temperature, wind-speed and increased moisture, could account for the rise in air-pollution levels. It is likely, though, that the odd-even measure introduced by Delhi’s Government might not, in itself, be adequate,” the report states.
According to IndiaSpend, the average PM 2.5 concentration in Delhi’s air was 361.3 micrograms per cubic metre between January 1 and January 7.
PM 2.5 concentration in Delhi’s air was much lower at 240.1 µg/m³ between December 25 and December 31, the report states.
A big reason behind the air quality no improving despite the restriction being in place is that wind speed has fallen consistently since December. Only on January 6 did it pick up. Strong winds have a major role in dispersing pollutants. Humidity, too, has been higher as compared to December. This also leads to an increase in the concentration of pollutants.
Hindustan Times had also reported on Friday that the concentration of PM 2.5 has seen a marginal decrease between 8 am and 8 pm – when the restriction is in place. The gains, however, are lost when an average of the pollution throughout the day is calculated.
According to Khetan, even if weather conditions are kept the same, the peak pollution level in January so far has been less than that in December and November.
“After the restriction, there has also been a reduction in the per capita emission of cars as occupancy rate has gone up,” Khetan said.