A recent study conducted by the Central Pollution Control Board (CPCB) has unveiled the persistently high pollution levels in India, with Delhi retaining its status as the most polluted city in the country, despite some reduction in air pollution. The study identified five out of the top 10 most polluted cities in India to be located in the National Capital Region (NCR), with an additional two in Bihar. The remaining three cities were situated in Assam, West Bengal, and Madhya Pradesh, as outlined in the CPCB report.
The top-ranking cities in terms of pollution were Delhi, Faridabad, Ghaziabad, Noida, and Meerut, all located within the NCR. Additionally, Patna and Muzaffarpur in Bihar featured among the top 10. Nalbari in Assam, Asansol in West Bengal, and Gwalior in Madhya Pradesh rounded out the list, according to the CPCB report.
The study, covering the period from October 2022 to September 30, 2023, recorded Delhi with the highest PM2.5 levels in India, measuring 100.1 µg/m³. This level was 3.3 times higher than the CPCB's 'good' level and 20 times higher than the World Health Organization's (WHO) safe limit. However, it represented a 4% improvement compared to the previous year (October 2021-September 2022), when the PM2.5 level was 103.9 µg/m³.
PM2.5 levels are measured in µg/m³, which stands for micrograms per cubic meter of air.
While other NCR cities on the top 10 list also showed improvements, Patna, Asansol, and Gwalior witnessed deteriorations in air quality during the same period.
During the peak pollution months from October to December, PM2.5 levels decreased in six of the top 10 most-polluted cities, including all NCR regions and Muzaffarpur. However, PM2.5 levels increased in Patna, Asansol, and Gwalior, signifying a worsening air quality trend.
Despite reductions in absolute PM2.5 levels in all NCR cities and Muzaffarpur, the levels remained above safe limits, posing significant health risks. Delhi, for instance, averaged 157.1 µg/m³, surpassing both the CPCB and WHO's 'safe' limits.
The CPCB report highlighted that air pollution is most severe during the winter months (from October to March) in Delhi, primarily due to factors such as cooler temperatures, low or no rainfall, fireworks, and stubble burning.
The study spanned from 2019, coinciding with the launch of the National Clean Air Programme (NCAP), to 2023, focusing on six major cities in India known for air quality challenges: Delhi, Mumbai, Kolkata, Bengaluru, Lucknow, and Patna.
While NCR cities showed declining trends in PM2.5 levels during the peak pollution months, PM2.5 levels increased across all regions from January to March 2023, indicating worsening air quality.
During the peak pollution months, Lucknow recorded a 32.6% drop in PM2.5 levels between 2019 and 2021, with a further 9.4% improvement in 2022. Delhi also displayed a steady 10% improvement in 2022 compared to the previous year. However, the air quality, with an average of over 157.1 µg/m³, remained a serious health risk.
Patna experienced a decreasing trend until 2021 but saw a sharp rise in 2022, reaching levels similar to those in 2019. Mumbai, Bengaluru, and Kolkata experienced rising PM2.5 levels from 2019 to 2022, indicating deteriorating air quality.
From January to March 2023, PM2.5 levels increased in several of the top 10 most-polluted cities, marking a contrast to the declining trends observed during the peak pollution months. Delhi, Noida, Meerut, Patna, Muzaffarpur, Asansol, and Gwalior all saw spikes in PM2.5 levels during this period.
Only Faridabad and Ghaziabad in the NCR region reported decreased PM2.5 levels, by 6% and 27%, respectively.
The CPCB report also included the top 10 cities with the cleanest air between October 2022 and September 2023. Aizawl, the capital of Mizoram, ranked first with a PM2.5 concentration of 11 µg/m³, followed by Chikkamagaluru in Karnataka (17.6 µg/m³) and Mandikhera in Haryana (17.7 µg/m³). This list encompassed areas monitored by the government's network of air quality monitors (CAAQMS), not limited to NCAP cities.
Karnataka was well-represented on this list, with eight cities featured among those with the cleanest air.
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