Arsenic has been detected in groundwater in parts of 230 districts in 25 states and fluoride in 469 districts in 27 states, Union Minister of State for Jal Shakti Bishweswar Tudu informed the Rajya Sabha on Monday.

In a written reply, the minister said that the ground water contamination reported by the Central Ground Water Board (CGWB) is mostly geogenic in nature and does not show significant change over the years.

The CGWB under the Ministry of Jal Shakti conducts regular monitoring and assessment of groundwater quality including ground water contamination of Arsenic and Fluoride. The board has carried out various studies in collaboration with other institutions, he said.

These studies indicate the occurrence of arsenic and fluoride in ground water beyond permissible limits -- set by the Bureau of Indian Standards -- for human consumption in isolated pockets in various states and Union Territories, he said.

Arsenic has been reported in parts of 230 districts in 25 states and Fluoride has been reported in 469 districts in 27 states.

CGWB along with the National Institute of Hydrology (NIH) prepared a report on “Mitigation and Remedy of Groundwater menace in India: A Vision Document” in 2010 and it has been circulated to various concerned agencies and departments for guidance and execution.

Recently, the CGWB signed a Memorandum of Understanding with the Geological Survey of India (GSI) for study of groundwater contamination, including arsenic and fluoride, with the focus on eight states -- Punjab, Haryana, Andhra Pradesh, Uttar Pradesh, Chhattisgarh, Jharkhand, Bihar, and Assam.

The studies conducted indicate the occurrence of arsenic and fluoride contaminations in various parts of the country which are mostly geogenic in nature, which means these constituents are already in the rock or soil matrix and get into the ground water through various chemical processes.

There is no conclusive evidence regarding the increase in concentration of the contaminants over time, he said.

He attributed the increase in the instances of arsenic contamination to revision of permissible limit of Arsenic in drinking water from 50 ppb to 10 ppb by the BIS in 2015 and increase in the number of sampling points.

Similarly, the increase in fluoride can also be attributed to increase in the number of sampling points over years taken up for monitoring.

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