The road-rationing plan was working and would not be cut short as pollution levels in the city had dropped considerably, the Delhi government said on Thursday, a claim not entirely backed by data.
A week into the 15-day trial run, the city government, battling criticism that the odd-even formula for private cars had failed to clean city’s dirty air, said concentration of particulate matter 2.5 (PM 2.5) had fallen significantly.
“Data shows that while average PM 2.5 concentration levels for December 2015 are around 465 micrograms per cubic metre, it is below 300 today,” transport minister Gopal Rai said, a day after the high court asked if the campaign could be restricted to a week. The government is to file its response on Friday.
Sixty micrograms per cubic metre is considered the maximum safe level while the World Health Organization recommends 25 micrograms. These tiny particles released by factories and motor vehicles can cause respiratory distress and have also been linked to cancer and heart disease.
HT found there was a marginal drop in pollution but the comparison was questionable. The December figures are from the Delhi Pollution Control Committee stations, while the data put forward by the government is from hand-held devices, often referred to as mobile stations.
HT analysed data from Mandir Marg and RK Puram stations for January 1-7 period and compared it with the averages provided by the government for December. The January figures are for the 12-hour duration — 8am and 8pm — when the restrictions are in place.
On January 6, PM 2.5 level at RK Puram was 412 micrograms per cubic metre. The average for December, according to the government, is 465.
On Thursday, PM 2.5 concentration was 467 at RK Puram in south Delhi and 474 at Mandir Marg in central Delhi. The latter is usually less polluted among the two.
According to scientists, the two figures are not comparable, as fixed stations record data the whole day while those with hand-held devices don’t spend more than 20 minutes at one location.
Concentration of pollutants also depends greatly on weather conditions such as temperature, humidity and wind speed. On Thursday, pollution levels spiked because humidity was higher than previous days.
Making a case for the campaign to run till January 15 as planned, Rai said, “We need to collect more data for better analysis. The government has made preparations; the people of Delhi are ready. The odd-even restriction will continue as planned.”
The government was forced to restrict the use of odd-numbered cars to odd dates and even-numbered to even dates after the high court compared Delhi to a gas chamber, voicing concern over alarming levels of air pollution.