A study conducted by the Central Pollution Control Board (CPCB) has found that the industries located in Haldia and Howrah add more to air pollution levels than those in Durgapur and Asansol. The study titled ~ Comprehensive Environmental Assessment of Industrial Clusters, was placed before the Union environment minister Mr Jairam Ramesh few days back and has created a stir among senior officials of West Bengal Pollution Control Board (WBPCB). They claim that according to a WBPCB study the Coke Oven plant of Durgapur Projects Limited (DPL) has been causing extensive air pollution in the area since more than 15 years and most of the units at DPL have been given closure order. The CPCB study classified industrial regions in India into two groups ~