According to a January 2016 report prepared by IIT-Kanpur, vehicular emissions were not the major cause of air pollution
While a 2016 report states that vehicular emissions were not the major cause of air pollution, a recent report from TERI shows that vehicular pollution is the cause of 28 % of PM2.5 emissions, thus contributing to be a major factor in air pollution
The Delhi government’s much-hyped odd-even scheme that was in place from November 4-15 was aimed at mitigating the increasingly deteriorating air quality in the Delhi-NCR region. Such a scheme was first introduced in January 2016 to cope with the then poor air quality in the region. The odd-even scheme was not extended beyond November 15 because the Delhi government felt that the air quality had improved significantly. However, the views of the Delhi government are in stark contrast to that of the Supreme Court who asserted that such an odd-even scheme may not be a permanent solution, especially when the Central Pollution Control Board (CPCB) says cars constitute around 3 % of pollution levels.
Further, the Supreme Court ordered the Delhi government to produce data and records of the previous years to show the effectiveness of the scheme. But it is interesting to note that different government agencies have offered diverse views on the impact of the odd-even scheme on air quality in Delhi-NCR.
According to recent data released by the Central Pollution Control Board (CPCB), the odd-even scheme coupled with high wind speed, reduced pollution levels in Delhi by 62 % during the day. A recent report from The Energy and Resources Institute (TERI) revealed that vehicular pollution contributes 28 % of PM2.5 emissions, thus panning out to be a major factor causing air pollution.
As per a January 2016 report prepared by IIT-Kanpur, vehicular emissions were not the major cause of air pollution. The CPCB had compiled special monitoring reports of time periods when odd-even was in force. According to the IIT-Kanpur study, four-wheeler passenger cars contribute to around 10 % of the total emission load of major pollutants PM2.5 and PM10. Theoretically, by reducing the number of private cars on Delhi's roads, there should have been a decrease in PM levels and a marginal reduction in road dust and secondary particulates, the 2016 report had stated. Data from the January 2016 report showed no clear trend in concentration of PM2.5 and PM10. The report revealed that meteorological conditions along with polluting sources outside Delhi, majorly damaged its air quality. The 2016 report concluded that while there was some reduction in air pollution due to the odd-even scheme, a single factor or action cannot substantially reduce air pollution levels in Delhi.
With limited data published in its analysis, Data Intelligence Unit (DIU) found that the situation at many stations during non-odd-even days (in 2016) was much better. For instance, at the DMS Shadipur pollution tracking centre, the average PM 2.5 level a week before implementation of the odd-even scheme was 103 but during the odd-even period, it rose to 174.5. The PM 2.5 levels also rose in the pollution centres at Netaji Subhas University Of Technology (NSIT), Dwarka and Institute of Human Behaviour and Allied Sciences (IHBAS), Dilshad Garden.
Similar situations prevailed during the implementation of the odd even scheme in April 2016, when PM2.5 and PM10 levels rose during the odd-even days at all stations. The IIT-Kanpur report was of the opinion that the air quality is affected by various meteorological factors such as mixing height, wind speed, temperature, solar radiation, relative humidity, conditions in the airshed outside Delhi, etc, besides emission from various sources including vehicles. The study stated that the decrease in vehicular emission was not a dominant enough factor to impact the observed data.
It was reported that Data Intelligence Unit (DIU) scanned records of AQI bulletins for Delhi during the time the odd-even scheme was implemented, and found that air quality worsened during both odd and even days.
According to the IIT-Kanpur study, from December 16-31, 2016 (15 days before odd-even), AQI levels in Delhi averaged 279.5, which came under 'poor' category, while during the odd-even days, AQI averaged 365.4, which came under 'very poor' category. It further stated that the situation worsened in the next 15 days when AQI averaged 373.6. Similarly, AQI averaged 258 (poor) between April 1 and 15, 2016. It rose to 283 during the odd-even days between April 16 and 30. Post the odd-even days, average AQI fell to 246. According to the report, statistics show that while the odd-even scheme helped in reducing congestion on roads, Delhi’s air, polluted by outer sources, could not be ameliorated by the odd-even scheme.
On the other hand, according to recent sources, TERI’s study shows that vehicular pollution is the cause of 28 % of PM2.5 emissions. Trucks and tractors generate 9 %, two-wheelers 7 %, three-wheelers 5 %, cars and buses 3 %, and light commercial vehicles 1 %. The TERI report further said dust pollution contributed close to 18 % of PM2.5 levels. Dust rising from roads contributed 3 %, construction dust 1 % and others contributed 13 %. Industries contribute 30 % to PM2.5 levels - power plants generate 6 %, brick kilns 8 %, stone crushers 2 % and 14 % from small industries, according to the report. In fact, stubble burning by farmers in Haryana, Punjab and western Uttar Pradesh, contributed only 4 % pollution during the winter season, stated the 2019 TERI report.