The odd-even formula has resulted in Delhi's lowest pollution peak compared to the previous high-smog episodes this winter, the government submitted on Friday before the Delhi High Court during the hearing of a public interest litigation.
The PIL was filed by Gunjan Khanna, a Noida-based restaurateur with businesses in Delhi and Manoj Kumar, managing partner of Hammurabi Solomon, a legal firm.
"This winter, out of all the severe smog episodes so far (with consecutive days in severe category), the peak pollution during odd-even programme has been the lowest...This shows that despite hostile weather conditions — no wind, dip in temperature and western disturbance — peak pollution during the odd-even scheme has been much lower," advocate Harish Salve, appearing for the Delhi government, told the court citing a report prepared by the Centre for Science and Environment (CSE).
The earlier smog episodes, said the CSE report, have seen much higher peaks and more rapid build-up compared to the rise that happened during the first week of odd-even programme. "This proves that reduced traffic volume has arrested the peaking of pollution. This validates the importance of this emergency action," he added.
This winter, according to the report, has witnessed extremely high level of pollution.
Typical winter conditions — cold temperature, lower mixing height of air, calm and no-wind conditions — trap air and increase pollution. This is why winter months require emergency measures.
The CSE report said the months of November and December last year show higher number of days in "severe category" — four times that of the safety standard — which is the worst category according to the National Air Quality Index (NAQI).
November 2015 had 73% of days in severe category, said the report, against 53% in November 2014.
December 2015 had 67% of days in severe category as against 65% in December 2014, which had at least 3% of days in good and satisfactory. But December 2015 had none.
"There has not been a single good air quality day this winter. On several consecutive days, the PM2.5 (particulate matter suspended in the air with a diameter of 2.5 micrometres) levels have remained in the worst category according to the (NAQI)," said the CSE report.
The odd-even programme, the government told the court, has been implemented as an emergency step to arrest the high peak level, when the overall pollution levels have gone five to six times higher than permissible limit.
"This is needed to protect public health in a city where every third child has impaired lungs," said Salve.
During odd-even days, claimed the government, daytime has shown faster drop in pollution which was notably higher before the implementation of the scheme.
"This brings out the clear impact of the odd-even scheme on pollution levels. Even when wind was not there to blow it away, the scheme succeeded in arresting the upward trend," said advocate Salve. He said both the real time pollution and wind data are from the Delhi Pollution Control monitoring stations.
'Pollution load from cars lower'
Both particulate and nitrogen oxide load from cars have reduced substantially during the odd-even programme by as much as 40%, claimed advocate Salve, referring to the CSE study.
"This indicates reduced exposure to toxic pollution from vehicles on roads. It is estimated by the US-based Health Effect Institute that the maximum impact of vehicular pollution is up to 500 metres from road side and 55% of Delhi's population live within that zone.
This has serious public health implications. Studies by researchers of University of California, Berkeley, have shown that in Delhi, the pollution level on the road and close to the roadside are at least 1.5 times higher and peaks 15 times higher than the ambient concentration. This programme has therefore contributed to the reduction in exposure to toxic fumes," said Salve, quoting from the report.
Moreover, higher occupancy of cars due to car pooling and sharing has also reduced per capita toxic emissions of car users substantially, said the CSE data.
"This is a significant contribution of Delhiites to the pollution control efforts that needs to be respected and encouraged for longer term solution," the report added.
A recent study by IIT Kanpur on assessment of Delhi's pollution sources has established that 'overall', vehicles are the "second largest" emitter of PM2.5 after "road dust".
Vehicles also emit gases like nitrogen oxides that convert to nitrate particles in the air and add to the overall PM2.5 levels in the city. This further enhances the role of particulates.
Cars are also the emitters of toxic pollutants. The IIT Kanpur study has shown that in different locations, diesel vehicles contribute hugely to PM2.5 from 60% to 90%.
According to the California Air Resource Board, the number of excess cancer cases per million people due to lifetime exposure to diesel fume is 300 as opposed to 29 for benzene that comes from petrol.
The CSE report said that the "Delhi government must be permitted to continue with the odd-even vehicle-rationing scheme and if these adverse weather conditions continue, then our recommendation is that the programme should also be continued".
CSE director general Sunita Narain told Firstpost, "It is true that pollution level has not gone down but had there been no ban on cars on the basis of this formula, the pollution level in Delhi would have been many times more."
In response to the arguments raised by advocate Salve, petitioners' counsel Shweta Bharti challenged the veracity of the data and submitted that it is "not in consonance with the recorded data as provided by the Central Pollution Control Board (CPCB) and Delhi Pollution Control Committee (DPCC)".
During the arguments, she handed over to court a copy of the Real Time Ambient Air Quality Data obtained by the DPCC website at 9:40 am on 8 January, depicting the constant presence of PM 10 and PM 2.5 was shown to be higher even after the implementation of odd-even formula.
"We pointed out that the DPCC data clearly depicts that even during the implementation of this formula, the pollution levels are constant and that there is no change whatsoever in the air quality," co-petitioner Manoj Kumar told Firstpost.
The court has reserved the matter for final orders on 11 January.