Despite the growth in contributing sectors, PM2.5 emissions for Delhi have decreased by 22 per cent in 2019 as compared to 2016 due to the closure of the Badarpur station, introduction of Euro-IV standards across India, ban on 10-year-old diesel vehicles, construction of eastern and western peripheral highways, and shift of industries to CNG.

This was stated by The Energy and Resources Institute (TERI) in its latest report on the cost-effectiveness of interventions for the control of air pollution in Delhi.

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However, in the NCR, PM2.5 emissions have only increased by 3 per cent as a decrease in emissions from residential and agricultural burning sectors has been compensated by increased PM emissions in the industrial sector, the report mentioned.

It added that the shift from petcoke to coal has on the one hand reduced SO2 emissions considerably, but has led to increased PM emissions due to the use of coal, which is high in ash content.

However, change in only PM2.5 emissions cannot be directly linked to PM2.5 concentrations, because of meteorology and also because of secondary particulate formations linked to Sulfur Dioxide (SO2) and Nitric Oxide (NO) emissions.

The projected emission inventory of 2019 has been fed into the air quality model (CMAQ) along with meteorological inputs from the Weather Research and Forecasting (WRF) model. Monthly PM2.5 concentrations were derived for the whole National Capital Region (NCR) including Delhi.

As per a pictorial representation done by TERI, higher concentrations of PM2.5 were recorded in winter in comparison to summer. “This can be attributed to lower wind speed and shallower boundary layer height leading to a reduction in the dispersive capacity of the atmosphere resulting in a higher concentration of ambient PM2.5 concentrations. High levels of pollution during winters are evident in the entire NCR, pointing towards the fact that air pollution is a regional scale issue. Summers are relatively cleaner, but still show PM2.5 concentrations above the standards in Delhi,” it added.

The study had estimated that PM2.5 concentrations in winter are expected to fall by 9 per cent, 21 per cent, and 28 per cent in 2022, 2025, and 2030 respectively, when compared to 2019, the base year of the study. Though the PM2.5 concentrations may fall marginally over the years, the levels will continue to remain significantly above the national standards of 60Ig per mA.