Perchlorate, chlorate and bromate in water samples from the South-West coast of India

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.