THE PILOT odd-even policy of the Delhi government may have ended on Friday but not without sparking a debate over the success of the first such initiative in the country to curb vehicular pollution.
While different agencies have released data based on different parameters to judge the results, they contain a common strand: Pollution levels dipped, even marginally, in the second half of the 15-day initiative.
Among the agencies that generated data were the Delhi Pollution Control Committee (DPCC) which relied on spot-monitoring through a mobile van besides its six stationary ambient stations, and the Supreme Court-appointed Environment Pollution Control Authority (EPCA) — both claimed a drop in peak levels of pollutants. The Central Pollution Control Board (CPCB), however, released data on 24-hour average values, which showed marginal dips only at certain locations.
Both methods had its supporters and detractors with Dr M P George of DPCC maintaining that studying peak levels was best because “the aim of the policy… is to bring down the spikes, or the sharpest rises in pollution”. But Dr B P Sengupta, former member secretary of CPCB, said “national standards are based on hourly, eight-hourly and 24-hourly averages and long-term annual averages, and ambient air quality standards”. “So comparing peaks or spot-monitoring reports with these standards is not scientific,” he said.
Approach 1: Peak levels
The Indian Express analysed peak values of four categories of pollutants associated with vehicular pollution — PM 10, PM 2.5, Nitrogen Dioxide (NO2) and Carbon Monoxide (CO). The safe limits, as defined by the National Air Quality Index (AQI), for PM 10, is 100 micrograms per cubic metre and 60 mg/cubic metre for PM 2.5.
* An analysis of particulate matter shows that peaks fell marginally in the first week of January only in one monitoring station — R K Puram — in comparison to the last two weeks of December. From January 1-7, peak levels of PM 10 fell to 976 mg/cubic metre from over 1000 mg/cubic metre and that of PM 2.5 to 662 mg/cubic metre from 796 mg/cubic metre. All other stations saw a spike.
* In the second week of January, particulate matter peaks witnessed a drop across all stations, barring Anand Vihar, when compared to January 1-7 data. At R K Puram, for instance, PM 10 peaks dropped to 648 mg/cubic metre, and PM 2.5 to 442 mg/cubic metre.
* A study of gaseous pollutant levels linked to vehicles shows peaks spiked in the first week of January and fell marginally in the second week. Safe limits for CO is 4 mg per cubic metre, for NO2 80 mg/cubic metre.
At Anand Vihar, peak levels of CO increased from 7 (December 25-31) to 10.4 mg per cubic metre (January 1-7). NO2 peaks increased from 159 to 266 mg/cubic metre in the same period. At Punjabi Bagh, peak CO levels increased from 4.9 to 7.20 mg/cubic metre and of NO2 from 144 to 263 mg/cubic metre in the same period.
* In the second week of January, peaks in gaseous pollutants dropped in some stations. In Anand Vihar, CO peaks dropped to 9.2 mg/cubic metre. But in Punjabi Bagh, peak levels of CO increased from 7.2 to 10.9 mg/cubic metre in this period.
Approach 2: Daytime, night-time levels
According to Dr Sarath Guttikunda, who heads an independent research group, UrbanEmissions.Info and is associated with IIT-Bombay, “On a daily basis, peaks can be very misleading because in Delhi, the night-time concentrations are higher due to strong meteorological inversion and more emissions from heating needs.” He said the best way to assess the scheme’s impact would be splitting 24 hours into day-time and night-time concentrations.
Now consider what average 24-hour data on PM 2.5 levels showed:
* The CPCB’s air quality lab analysis of 24-hour average data between January 1-13 for PM 2.5 shows marked dips in the second week of January. A majority of the monitoring stations — Northeast Delhi, South Delhi, Southeast Delhi and West Delhi — reported spikes till January 3-4 and then sharp drops.
* In Anand Vihar, Punjabi Bagh and Anand Vihar, the drops were drastic — of about 200 mg/cubic metre. But after January 9, the 24-hour average levels across stations rose, peaking on January 11. After a marginal fall on January 12, PM 2.5 levels spiked again on January 13.
Scientists, however, cautioned against these trends being interpreted as a result of the odd-even policy. “Meteorology has played a strong role this year and neither the drops or the spikes can be interpreted on the basis of emissions alone. However, it may be possible to say that average levels of PM 2.5 would have spiked further had emissions not been controlled,” said Dr Dipankar Saha, in-charge of CPCB’s air quality lab.
Approach 3: Air Quality Index
An analysis of the AQI, the national indicator of the quality of air we breathe, for two-week periods from December-January corroborates the dip:
* Anand Vihar, with high particulate matter due to its proximity to the inter state bus terminal, experienced 12 days categorised as ‘severe’ between December 1-15, and 13 such days between January 1-15. Between December 15-30, only eight such days were recorded.
* Mandir Marg experienced five ‘severe’, four ‘very poor’ and two ‘poor’ days between January 1-15. Between December 1-15, 10 ‘poor’ days were recorded, with only a single ‘very poor’ day. At R K Puram, ‘severe’ days increased from three to eight in this period.
* Dwarka had five ‘satisfactory’ days between December 15-31, and three ‘moderate’ days between December 1-15. But during January 1-15, only ‘severe’, ‘very poor’ and ‘poor’ days were recorded.
* In Punjabi Bagh, there were seven ‘severe’ days from December 1-15, and only five ‘severe’ days between January 1-15. The AQI is based on calculating prominent pollutant values of ambient air quality. And while the above data seems to indicate no improvement, scientists say this may not be the best way to assess the policy.
EPCA findings: Smog down, roadside exposure dipped
So what did the policy really achieve? The clearest possible indicators lie in the findings of the EPCA:
* Peak smog episodes witnessed lower pollution levels. During smog episodes, PM 2.5 on January 3 was recorded at 391 mg/cubic metre against 525 on December 4 and 606 on November 12.
* Roadside exposure of pollutants dipped, according to DPCC’s mobile monitoring data.
* According to Centre for Science and Environment analysis, the NOx (NO and NO2) load from diesel during the first week of the scheme came down from 7.5 to 4.5 tonnes per day. The PM load from diesel came down from 0.47 to 0.27 tonnes per day.
* Car-pooling and sharing reduced per capita toxic emissions of car users substantially.
* A survey of traffic volume and speed by School of Planning and Architecture at 11 locations during the first few days found that travel time has reduced by 35 pc. TERI studied average speeds on NH24 and found speeds increased considerably.
Life after plan: Making reports and resuming regular duties
New Delhi: As the Delhi government’s odd-even plan for private vehicles came to an end Friday, all departments concerned started compiling final reports, to be submitted during a review meeting chaired by Chief Minister Arvind Kejriwal Monday.
Meanwhile, the 1,200 private buses used for public transport during the odd-even scheme will be shifted out of the DTC’s bus depots soon. Civil defence volunteers, deployed at nearly 200 locations in the city to persuade people to follow the odd-even rule, will also go back to their regular duties.
Most of the 66 teams of “enforcers”, deployed on major roads to impose fines on violators, will be disbanded. The helplines to address queries during the odd-even plan — 011-42400400 and 011-41400400 — can now be used to report complaints against buses and auto-rickshaws.
Traffic policemen will also resume their regular duties. ENS
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