Status of groundwater arsenic contamination in all 17 blocks of Nadia district in the state of West Bengal, India: A 23-year study report

• Arsenic contamination of groundwater in all 17 blocks of Nadia, India.
• People exposed to contaminated water, may suffer from skin lesions and cancer.
• Arsenic and iron in groundwater with depths, arsenic in biologic samples.
• Dermal and neurologic effects of arsenic, arsenical toxicity in children.
• Results are compared with two highly affected districts of West Bengal.

SummaryA comprehensive study was conducted in Nadia, one of the nine arsenic (As) affected districts in West Bengal, India to determine the extent and severity of groundwater As contamination and its health effects in particular, dermatological effects and neurological complications. We collected 28,947 hand tube-well water samples from all 17 blocks of Nadia district and analyzed for As by the flow injection-hydride generation atomic absorption spectrometer (FI-HG-AAS). We found 51.4% and 17.3% of the tube-wells had As above 10 and 50 μg/L, respectively and observed that groundwater of all 17 blocks contained As above 50 μg/L with maximum observed level of 3200 μg/L. We estimated that about 2.1 million and 0.6 million people could be drinking As contaminated water above 10 and 50 μg/L, respectively, while 0.048 million could be at risk of drinking As-contaminated water above 300 μg/L, the concentration predicted to cause overt arsenical skin lesions. We screened 15,153 villagers from 50 villages and registered 1077 with arsenical skin lesions resulting in a prevalence rate of 7.1%. Analyzing 2671 biological samples (hair, nail and urine), from people with and without arsenical skin symptoms we found 95% of the samples had As above the normal level, indicating many people in Nadia district are sub-clinically affected. Arsenical neuropathy was observed in 33% of 255 arsenicosis patients with 28.2% prevalence for predominant sensory neuropathy and 4.7% for sensorimotor. As groundwater is still the main source of drinking water, targeting low-As aquifers and switching tube-well from unsafe to nearby safe sources are two visible options to obtain safe drinking water.