Its been worth the effort after all. A soon-to-be-relased study by the Central Pollution Control Board (CPCB) has concluded that pollution levels in Delhi have shown a consistent decline since 1996.Called "Vehicular Pollution Control in Delhi, Initiatives and Impacts" the study says that pollution levels peaked in 1996 when emission norms were first made stringent. That year was the first time that fuel quality specifications were made stricter for diesel and petrol. Since then, every time new vehicular emission norms have been enforced, pollution levels have gone down. The study is expected to be released by the end of this month.