Four Decades of M C Mehta Litigation Transforms Delhi Air Quality Governance

The M C Mehta pollution case, originating from a 1985 oleum gas leak, has over four decades forced Delhi to shut coal plants, convert its entire public transport fleet to CNG and leapfrog emission standards from Euro 0 to Bharat Stage 6. Analysis of the city's five oldest air quality monitoring stations shows PM2.5 levels have fallen 46 per cent since 2012 as a direct result of court-mandated interventions.

Beginning with M C Mehta's 1985 writ petition following the Shriram Fertilizer oleum leak, the Supreme Court progressively expanded the case's scope to cover Delhi's entire transport, industrial and energy matrix. The court established that Article 21's Right to Life includes the right to a clean environment, invoked the Precautionary and Polluter Pays principles, and created the Environment Pollution Prevention and Control Authority as an expert advisory body. Mandates included closing all four of Delhi's coal-fired power plants, banning coal and furnace oil across industries, and requiring the entire public transport fleet to switch to CNG.

The case produced measurable environmental outcomes. Diesel's share in Delhi's transport energy mix fell from 40 per cent in 2015-16 to 20 per cent in 2023-24, while diesel cars' market share dropped from 35 per cent to less than 7 per cent. All legal industries in Delhi have transitioned to piped natural gas. The Graded Response Action Plan institutionalised emergency responses during severe winter smog. The judicial framework subsequently extended to 13 other highly polluted cities and triggered national SOx and NOx emission standards for 16 industrial groups.

As the Supreme Court moves toward disposing of the M C Mehta case, analysts warn that Delhi still requires a further 60 per cent reduction in pollution to meet clean air standards. The commentary calls for the executive to enforce hard mandates and strict milestones to sustain momentum. The case's legacy demonstrates that proactive judicial intervention, supported by an empowered scientific advisory ecosystem and civil society pressure, can break policy paralysis and accelerate clean energy transitions in megacities, providing a replicable model for other Indian cities.

Key figure — 46 per cent reduction in PM2.5 levels at Delhi's five oldest monitoring stations since 2012