Nearly half of the groundwater samples lifted from Delhi have been found contaminated and unfit for drinking, Parliament was informed today. In a written reply in the Rajya Sabha, Minister of State for Environment and Forests Babu Lal Marandi said, as per a Central Groundwater Board study in 1998, about 45 per cent of the 303 samples lifted from various structures and at different depths and locations in Delhi were found contaminated by nitrates, fluoride and trace metals.