Hyderabad, July 6: Non-governmental organisations have demanded that government should obtain environmental clearance from the centre before taking the up metro rail project in Hyderabad. They said noise pollution would be much more throughout the day even at the silent zones such as schools and hospitals. According to them, the metro rail will cause more than permissible level of noise in city. The voluntary organisation "Concerned Citizen" on Sunday organised a debate on the subject in which both the representatives of NGOs and officials of Metro rail projects participated.