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The second phase of the odd-even scheme, implemented to improve Delhi's air quality, saw a "rise" of nearly 23% in pollution levels compared to the first 15 days of April when the scheme was not in force, a study has claimed.
The study by IndiaSpend, a portal that runs a network of 'low cost sensors' across the national capital, based its findings on the volume of fine respirable pollutants – PM 2.5 and PM 10 – not taking into account gaseous pollutants such as ozone which is being monitored by few agencies.
The report said that the average PM 2.5 and PM 10 concentrations in the city's air were 68.98 and 134.39 micrograms per cubic metre (ug/m3), respectively, between April 15 and 29, indicating moderate conditions, as against 56.17 and 110.04 ug/m3 during the first 15-days of the month.
The corresponding safe limits of these extremely harmful pollutants, measuring less than 2.5 microns (approximately 1/30th the average width of a human hair) and 10 microns, respectively, are 60 and 100 ug/m3.
The other agencies which are involved in monitoring the city's air quality include Delhi Pollution Control Committee and Centre's System of Air Quality and Weather Forecasting and Research and organisations such as CSE and Teri.
The report, based on hourly averages, noted that pollution was at its worst at 7 am everyday, in line with the explanation provided by many experts that early morning hours are more polluted as pollutants build up through the night due to favourable weather conditions and truck traffic.
"Evening 5 pm was the best hour for Delhi during the odd-even phase, with PM 2.5 levels at 21 ug/m3, indicating 'good' air quality," it said
Transport sector of the national capital produces six times as much greenhouse gas emissions as that of Kolkata's, five times as much as Ahmedabad's and three times as much as Greater Mumbai and Chennai, the portal said advocating steps to improve the public transport system.
