Occurrence of perchlorate (ClO4), chlorate (ClO3) and bromate (BrO3) in public drinking, open well and surface water sources at 20 locations in the South-West coastal state of Kerala (India) is reported. The analysis was performed by high performance liquid chromatography interfaced with tandem mass spectrometry (HPLC–MS/MS). Irrespective of water source (public tap water, open well water and surface water) all the analyzed samples contained high levels of ClO4, indicating its contamination throughout the region. The highest ClO4 level found was 91.4 μg/L, which is 3.7 times higher than US EPA recommendations. ClO3 and BrO3 were also detected in the samples, with highest concentrations of 177 and 5.34 μg/L respectively in tap water samples. Regression analysis showed moderate positive correlation between ClO4 and bromide (Br) in tap water (r2=0.659) and open well water (r2=0.485) samples, respectively. Similar correlation was also observed between ClO4 and Cl (r2=0.591) concentrations in well water samples, indicating sea water could be one of the probable sources in addition to ClO4 manufacturing in the area. This is the first report of high levels of ClO4 and ClO3 and detectable BrO3 in water samples from anywhere in India.

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