Arsenic in the groundwater of Majuli – The largest river island of the Brahmaputra: Magnitude of occurrence and human exposure

• Arsenic contamination of groundwater in the largest riverine island Majuli, India.
• 37% and 16% of 380 tube-well water samples had As greater than 10 and 50 μg/L.
• 90% of urine, 100% of hair and 97% of nail samples had As above the normal ranges.
• Significant correlations between arsenic in water and As in hair, nail and urine.
• Arsenic concentration in bore-hole sediment was 0.2–1.44 mg/kg.

SummaryArsenic (As) concentrations in tube-well water, sediment, and biological samples, including hair, nail and urine were measured to determine the degree of contamination in groundwater and its impact on local inhabitants in the largest populated riverine island Majuli, Assam, India. Arsenic in the groundwater (n = 380) ranged from <3 to 468 μg/L with 37.6% and 16% of the samples having As above 10 μg/L and 50 μg/L, respectively. Arsenic concentration in the groundwater gradually decreased beyond 25 m depth of tube-wells. Nearly 90% of urine, 100% of hair and 97% of nail samples had As above the normal ranges, but mean As concentrations in hair, nail and urine of Majuli residents were lower than those in other contaminated areas of the Ganga-Meghna-Brahmaputra Plain. Significant positive correlations were observed between As in drinking water and As concentrations in hair, nail and urine samples (r = 0.71–0.78). The range of As concentration in bore-hole sediment was 0.29–1.44 mg/kg. The correlation between As and iron in sediment was found to be very poor. Hydrogeological studies are required to understand the source and mobilization process of As in groundwater of Majuli. Early mitigation measures are urgently needed to save the inhabitants of Majuli from arsenic exposure and possible health effects.