Vehicles top polluters in Delhi during Diwali week: CSE assessment

According to a CSE assessment of Delhi’s Diwali pollution levels this year, cars accounted for the majority of the capital’s local pollution sources and contributed to half of Delhi’s own contribution to PM2.5 concentration in the week of 21–26 October. Vehicles played a significant influence in the day-long congestion that during that week almost completely eliminated the gap between peak and non-peak hours. These preliminary results for the Diwali week of 2022 are consistent with those of a comparable analysis done for various times during the winter of the previous year (2021).
“A city with 1.4 crore registered vehicles (as per the VAHAN database) and an annual addition of five lakh vehicles a year (of which 97 per cent are personal vehicles, mainly two-wheelers and cars), has failed to build transportation strategies to scale for transformative changes. With more than 200 lakh population (estimate of World Population Prospect by the UN, 2018), the city is estimated to be generating at least 276 lakh daily travel trips. If most of these commuting trips have to be self-organised with personal vehicles, Delhi cannot meet the clean air target or the benchmarks for liveability,” says Anumita Roychowdhury, executive director, research and advocacy, CSE.
An examination of the Decision Support System (DSS) for Air Quality Management of the Indian Institute of Tropical Meteorology (IITM), Pune’s dynamic assessment of hourly source contribution to PM2.5 concentrations. This offers numerical data on the contribution of emissions from Delhi’s own sources as well as the 19 districts around it in the National Capital Region (NCR) and beyond. This trend is suggestive because data for the 22nd, 26th, and 23rd of October are accessible until 14:30 and 15:30, respectively.
An analysis of hourly traffic speeds with the help of real time data from Google Maps to assess the level of congestion on 15 major arterial roads. The speed has been taken as a proxy for congestion and not to advocate high speed motorized traffic.
Vehicles’ contribution to Delhi’s PM2.5 concentration was maximum during the week. Taken together with other sources (such as biomass and pollution from NCR and other districts plus Delhi’s own local sources), vehicles contributed nearly 17 per cent of the total PM2.5 concentration in the city. But if only Delhi’s local sources are considered, the transport sector topped the ranks (see Graph 1 in report), with vehicles contributing around half of the PM2.5 concentration from local sources. The indicative data shows that their daily share varied between 49.3 percent to 53 percent during that week.
This was followed by household pollution (residential) at 13 percent, industries at 11 per cent, construction at 7 per cent, waste burning and the energy sector at 5 per cent each, and road dust and other sources at 4 per cent each. “This observation is consistent with the trends evaluated during the previous winter in Delhi,” says Vivek Chattopadhyay, principal programme manager with CSE’s Clean Air and Sustainable Mobility unit.