India, March 13 -- At 80, MC Mehta has a simple formulation for the cause he has pursued for four decades. "People cannot manufacture clean air. Even if we spend billions of dollars, pollution will still leave its impact. Clean air is the basic right of every human being and every animal. It is not negotiable," he told HT on Thursday, hours after the Supreme Court formally disposed of the writ petition he filed in 1985.

That petition - WP(C) No. 13029/1985 - became the vehicle for the most sustained judicial intervention on urban air quality anywhere in the world.

Over nearly 40 years, it produced the orders that converted Delhi's bus fleet to CNG, phased out leaded petrol, created the Environment Pollution (Prevention and Control) Auth...