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A study of eight metropolitan cities by the Central Pollution Control Board (CPCB) indicates that ground water may not very safe for drinking when compared with India's lax drinking water standards.

The concentration of Chloride was found to be higher than 1,000 mg/litre in five cities --- Chennai metropolitan city, Vijaiwada, Coimbatore and Agra. Coimbatore, however, has the highest quantity of chlorides --- 18 per cent of samples - above the permissible limit. Chennai and Agra has over 50 per cent of samples above the desirable limit.

These five cities also had very high concentration of total dissolved solid. In Agra, 38 per cent of samples were found to be above the permissible limit and over 96 per cent of samples above the desirable limit. In Madurai, not even a single sample was found below the desirable limit.

The CPCB has finalized reports for eight of the 24 cities for which the study Groundwater Quality Assessment 2006-07 was conducted. The samples were picked from tubewells, hand pumps and dug wells, primarily used for drinking purposes.

In the first national study of its kind, CPCB found Nitrate concentration to be higher than permissible limit in Agra, Coimbatore and Agra, whereas it was within permissible limit in other cities.

Similarly, concentration of fluoride was found to be above the permissible limit in Agra, Vijaiwada, Chennai, Mudurai and Coimbatore. But, Agra has highest number of samples (82 per cent) above the permissible limit.

Bacterial content in water indicated by the coliform bacteria was found to be within permissible limit except for Lucknow and Meerut Metropolitan cities.   

The study also hints at poor sewerage as a major reason for contamination of ground water used for drinking, said a senior scientist with CPCB. For instance about 200 million litres of sewage every day is discharged into open in Agra every day. There is also ground water contamination because of industrial activity effluents from where are not treated before discharge into the drains.

According to CPCB, the report highlights the concern over poor quality of ground water leading to health problems. The groundwater in most cases serves the poor and unplanned localities in the cities, the CPCD scientist said.