How did Mumbai fare in air pollution in 2024?

Mumbai: Air pollution has dominated conversations in Mumbai recently, with hazy skies and a pall of gloom shrouding the city’s skyline. Amidst these concerns, new data accessed from the Central Pollution Control Board (CPCB) and analysed by climate research startup Envirocatalysts offers a surprising insight: Mumbai’s air quality in 2024 showed marked improvement compared to the past five years, nearing pre-pandemic 2019 levels.

A cleaner 2024?

Daily air quality index (AQI) readings at midnight painted an optimistic picture. The city recorded only one day of ‘poor’ AQI in 2024—on November 2, attributed to Diwali firecrackers. A few other days came close, such as November 1 (AQI 190) and November 24 (AQI 180), but these did not breach the ‘poor’ threshold. Most days fell within the ‘moderate’ range, with 148 such days logged. Additionally, 130 days were categorised as ‘satisfactory,’ and 87 days achieved the ‘good’ benchmark.

Annual average concentrations of pollutants, including PM2.5, also improved, falling below the National Ambient Air Quality Standards (NAAQS) after three consecutive years of exceeding them. However, experts caution against interpreting these numbers as a complete success.

Weather or policy?

According to Sunil Dahiya, founder of Envirocatalysts, a mix of favourable weather conditions and improved mitigation measures contributed to the better AQI. “Post-lockdown activities, such as rampant construction and increased reliance on private vehicles, worsened air quality,” Dahiya explained. “The Brihanmumbai Municipal Corporation’s (BMC) Air Pollution Mitigation Plan, initiated in 2023, seems to have made a difference, although it is hard to quantify its impact.”

Stricter vehicle emission standards under Bharat Stage 6, introduced in 2020, also played a role. However, Dahiya noted that the benefits of these measures are often offset by the ever-increasing number of vehicles on the roads.

Mumbai’s coastal location gives it a natural advantage in air pollution dispersal, but even this can be influenced by global weather phenomena. “We anticipated worse air quality in 2024 due to the delayed onset of La Niña,” said a professor from the National Institute of Advanced Studies, Bengaluru. La Niña—marked by cooling Pacific Ocean temperatures and altered wind patterns—can trap pollutants and exacerbate air quality issues. “While La Niña’s delayed onset provided some respite, its prolonged intensity remains a concern, especially in the context of climate change.”

Also read: Dense fog disrupts air, rail traffic as Delhi’s air quality worsens amid chill

Experts like SN Tripathi from IIT-Kanpur agree that weather conditions significantly influence Mumbai’s air quality. However, parsing the impact of weather versus mitigation efforts remains a challenge. Sachin Ghude, Project Director at SAFAR (System of Air Quality Forecasting and Research), emphasised that Mumbai’s air quality trends remain unpredictable. “Vehicular movement and construction activities in Mumbai and Delhi are comparable, yet Mumbai’s air quality benefits from its coastal geography,” he added.

‘Moderate’: The new normal?

Not everyone shares the optimism surrounding the 2024 data. Tuhin Banerji, a scientist at the Bombay Environment Action Group (BEAG), argued that ‘moderate’ AQI is far from acceptable. “Ideally, daily AQI should fall within the ‘good’ category. However, given current pollution levels, this seems unattainable except during the monsoon,” he remarked.

Banerji also highlighted the disparity in air quality across different parts of the city. While the overall AQI may seem ‘moderate,’ some areas recorded ‘poor’ or even ‘severe’ AQI for prolonged periods. The rise in monitoring stations from nine in 2019 to 29 in 2024 provides a more comprehensive picture but also averages out the most polluted spots.

A cautionary note

While acknowledging the improvement, Dahiya stressed that Mumbai’s air is still far from healthy. “Even when pollutant levels meet NAAQS standards, they remain seven times higher than WHO guidelines,” he warned. “Adverse health effects occur even below NAAQS thresholds. Mumbai’s coastal geography presents a unique opportunity to set more ambitious targets and reduce the public health burden.”