From CK Nayak
NEW DELHI, Nov 27: Contrary to popular perception, several hill states — including Meghalaya — have higher annual mean pollution levels, surpassing the national average and far exceeding World Health Organization (WHO) standards, according to a report released here today.
As expected, Delhi ranked as the most polluted among 33 states and Union Territories, with an annual mean PM2.5 concentration of 101 micrograms per cubic metre — 2.5 times the Indian standard and 20 times the WHO guideline, the report by the independent research organisation Centre for Research on Energy and Clean Air (CREA) stated.
Delhi was followed by Haryana at 63, Tripura at 62, Assam at 60, Bihar at 59, West Bengal at 57, Punjab at 56, Meghalaya at 53 and Nagaland at 52. All of these exceeded the national standard, according to the satellite-based analysis conducted from March 2024 to February 2025.
In several states, every monitored district breached the National Ambient Air Quality Standards (NAAQS). These include Delhi, Assam, Punjab, Haryana, Chandigarh, Himachal Pradesh, Meghalaya, Tripura and Jammu & Kashmir.
PM2.5 — particulate matter measuring 2.5 micrometres or smaller — can penetrate deep into the lungs, enter the bloodstream, and cause a range of health issues. It can worsen asthma, trigger coughing, wheezing and difficulty breathing, and is linked to an increased risk of heart disease and other cardiovascular problems. High concentrations also reduce visibility and have been associated with low birth weight and premature mortality.
Overall, 447 of the 749 districts analysed (60 per cent) exceeded the NAAQS limit of 40 micrograms per cubic metre for annual PM2.5. The most polluted districts were concentrated in a few states. Delhi (11 districts), West Bengal (2) and Assam (11 districts) together accounted for nearly half of the top 50, followed by Bihar (7) and Haryana (7). Other contributors included Uttar Pradesh (4), Tripura (3) and Rajasthan (2).
Particulate matter is a mixture of solid and liquid particles suspended in the air, including dust, soot and smoke. At 2.5 micrometres or less in diameter, these particles are more than 40 times smaller than the width of a human hair.
Major sources of PM2.5 pollution include vehicle emissions, industrial processes and wood burning. Natural events such as wildfires, dust storms and volcanic eruptions also release PM2.5. Even everyday indoor activities — including cooking, burning candles or incense — contribute to elevated levels.
