Delhi: Dust, ozone to blame for summer pollution, say experts

Delhi: 6 April, 2022 (Times of India)


NEW DELHI: The capital is set to get a summer action plan to deal with pollution levels from April to September soon, but data shows it does not meet the national ambient air quality standards on most days during the season, i.e., from April to June.


The city’s overall air quality index (AQI) has been hovering in the ‘poor’ category since April 1. Compared with winter, summer witnesses reduced pollution as the weather warms up and wind picks up speed. Experts said dust and ozone are the main causes of pollution in summer.

Ozone is produced from a complex interaction between nitrogen oxides (NOx) and volatile organic compounds (VOCs) that are emitted from vehicles, power plants, factories and other combustion sources and undergo cyclic reactions in the presence of sunlight to generate ground-level ozone. Local dust lifting and regional transport of wind from dry arid regions increases in this season due to temperature and wind pattern. VOCs can also be emitted from natural sources, such as plants.

Anumita Roychowdhury, executive director, research and advocacy, Centre for Science and Environment (CSE), said, “Summer pollution has different characteristics. While the share of wind-blown dust increases in particulate concentration, gaseous emissions from vehicles, industry and open burning contribute to increased formation of ozone under the influence of sunlight. Ozone is highly reactive and harmful gas and needs urgent action to control emissions from vehicles and industry and evaporative emissions from fuel systems. Carrying out repairs, paving and greening of road networks, scaling up afforestation and forest protection is also required.”

Gufran Beig, founder project director, System of Air Quality and Weather Forecasting and Research (SAFAR), the forecasting body under the Union ministry of earth sciences, said, “In addition to local sources, dust is one the main sources of pollution. Dust storms and local dust lifting get aggravated with increased temperature and hot winds.”

According to an analysis by CSE, the monthly average level of PM2.5 in April and May 2021 — the hard lockdown phase — was higher than the corresponding levels in April-May 2020 — also a hard lockdown phase.

Another CSE report said the 2021 summer had 90 days with six or more stations exceeding the eight-hour standard of ozone, which is identical to the 2019 summer and 10 days more than 2020 summer, despite the fact that the 2021 summer was one of the mildest in recent years with no severe heatwaves.