Deonar, Sion Air Pollution Worse Than Chennai Despite Coastal Location
A recent national-level study has placed Mumbai’s Deonar and Sion neighbourhoods among the worst coastal air quality zones in India, outpacing even non-industrial cities like Puducherry and Chennai in pollution intensity. The report, released by the Centre for Research on Energy and Clean Air (CREA), analysed PM2.5 data from January to June 2025 across 239 cities equipped with Continuous Ambient Air Quality Monitoring Stations (CAAQMS).
Although Mumbai’s average PM2.5 concentration remained technically below India’s national threshold of 40 μg/m³ during this period, several localities — notably Deonar, Sion, Kandivli East, and Bandra-Kurla Complex — consistently registered pollution levels above or equal to this limit. This indicates that hotspot pollution in specific Mumbai zones now rivals or surpasses that of inland urban centres. The findings challenge the common assumption that coastal cities enjoy cleaner air due to their proximity to sea breezes and higher humidity levels. According to CREA analyst Manoj Kumar, “Mumbai’s persistent pollution across multiple sites contrasts starkly with cities like Chennai and Puducherry, where residential and peripheral areas report significantly lower PM2.5 levels.”
Deonar’s inclusion as a high-risk zone is unsurprising. The locality hosts one of Asia’s oldest and largest landfills, known for frequent fires and methane build-up, contributing heavily to localised air pollution. The adjacent Sion neighbourhood, surrounded by traffic corridors and informal industrial zones, shares similar exposure. These microenvironments make Mumbai a paradox — a coastal city plagued by chronic inland pollution dynamics. According to the study, PM2.5 particles, a known carcinogen, remain especially hazardous due to their ability to enter the bloodstream via the lungs. The health implications are long-term and severe, ranging from respiratory illness to cardiovascular disease. This raises public health alarms, especially in dense urban settings like Mumbai where millions are exposed daily.
Across the country, the study found that 122 out of 239 cities exceeded India’s annual PM2.5 limit, while all 239 surpassed the World Health Organization’s (WHO) more stringent benchmark of 5 μg/m³. “This means that even the cities appearing to ‘comply’ with national standards are far from achieving safe air quality as per global norms,” Kumar warned. Experts now urge a shift from seasonal, crisis-based interventions to comprehensive, year-round air quality management. Environmentalists also highlight the need to expand India’s National Clean Air Programme (NCAP) to include gaseous pollutants and enforce sector-specific action plans, especially for transport, construction, and waste burning.
While cities like Vijayawada and Puducherry show promising results with significantly lower PM2.5 averages, Mumbai’s high pollution levels are more consistent across various locations, calling for a deeper structural fix. The findings place Mumbai in an urgent policy spotlight. Unless hotspot-specific air quality action plans are fast-tracked and enforced, residents in zones like Deonar and Sion will continue to face disproportionate health burdens despite the city’s coastal advantage.
