NEW DELHI: Despite a slight improvement in air quality over the past year, Delhi was very polluted with high PM2.5 levels, according to Climate Trends and Respirer Living Sciences. Their study said that Delhi and four other NCR towns — Faridabad, Ghaziabad, Noida and Meerut — were among Indias top 10 polluted cities.According to the study, between October 1 last year and September 30 this year, Delhi recorded an average PM2.5 concentration of 100.1 micrograms per cubic metres — thrice the governments standard of 30 and 20 times the safe limit of 5 micrograms defined by the World Health Organization. Following Delhi were Patna and Muzaffarpur, both in Bihar, with 99.7 micrograms per cubic metre.Track the pollution level in your cityThe cleanest air was deemed to be in Aizawl, Mizoram, where the PM2.5 level was 11.1 micrograms per cubic metre.Assessing the six major state capitals facing the challenge of clean air during the peak pollution months between October and March from 2019 to 2023, the study found that Mumbais air worsened steadily while Delhis and Lucknows improved. From October 1, 2023, a revised version of Graded Response Action Plan has come into force in Delhi and 24 nearby districts, collectively known as the National Capital Region. The region has several places which frequently top Indian and global air pollution rankings.Delhi saw a 4% improvement in air quality over the previous year between October last year and September this year. The other NCR cities in the top 10 too showed significant improvement in air pollution during this period: Ghaziabad 25%, Faridabad and Noida 12% and Meerut, 11%.The study analysed two sets of air quality data, first the PM2.5 data for the past one year from October 1, 2022, to September 30, 2023, to track improvement in air quality. The second data comprised PM2.5 readings during winter, roughly October–March when pollution levels are high. It said that pollution in cities like Delhi was highest during the winter months because of factors like cooler temperatures, low or no rainfall, stubble burning and bursting of firecrackers.In the peak pollution months of October-December 2022, the PM2.5 levels dropped in six of the top 10 cities — Delhi, Faridabad, Noida, Ghaziabad and Meerut in NCR and Muzaffarpur in Bihar — indicating an improvement in air quality over the previous year. How much of this was due to climatic factors (rain, wind) and how much due to policy intervention is a matter of deeper study, the study said.However, despite the decline, the absolute PM2.5 levels in these places are extremely high and pose serious health risks. In Delhi, it averaged 157.1 microgram per cubic metre in October-December 2022. The figure was 174.4 in the same period in 2021, 180.5 in 2020 and 176.9 in 2020.

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