THE THICK black smoke emanating from Calcutta factory chimneys in the 19th century was considered by many as a sign of prosperity. The Calcutta and Howrah Smoke Nuisances Act passed in 1863 aimed principally at land-based engines and was not very effective, producing no more than six prosecutions in a year. It remained almost a dead letter till 1879, when public protests forced Ashley Eden, the Lieutenant Governor of Bengal, to intervene and set up a committee to look into the smoke problem.

In 1892, G E Marklew, a jute warehouse inspector, was appointed part-time special smoke inspector, a post in which he was made permanent in 1901. He used diagrams of four shades to approximate the colour of smoke, recorded the density and duration of chimney emissions, issued warnings to managers and initiated prosecutions. Indian managers were readily prosecuted after a few warnings while European managers could expect greater forbearance. And, some of the most important polluters, including the government-owned mint and water pumping stations, got away scot-free.

But the British realised environmental regulations don't succeed unless they are participatory. This was manifest in the new Bengal Smoke Nuisances Act of 1905, and the setting up of the Bengal Smoke Nuisances Commission, which had representatives from the industry and the bureaucracy. An important concession on the insistence of the Bengal Chamber of Commerce was the reduction of the fine in the first conviction from Rs 1,000 to Rs 50. The new system also linked prosecution with quantified levels of smoke.

Instead of relying on subjective perceptions, a series of grey scales based on those developed in France by Ringelmann was used to monitor smoke. The scales could not be used to detect sulphur dioxide or other "invisible pollutants," but they were far more sophisticated than those used in London, where Ringlemann scales were introduced only in 1956.

As a result of this scientific approach, pollution standards were set according to what industry could achieve and not according to what people could bear. "Clean" mills -- those with the lightest smoke -- were taken as the norm. Those who suffered were the engine stokers, especially the Indian ones, who were held responsible for smoke emissions and punished with fines and dismissals. That the engines were of poor quality was never considered.