National Institute of Occupational Health (NIOH), ICMR
Dr. Syed Shakeel Ahmad Zaidi, Scientist E & Head, Department of Biochemistry, National Institute of Occupational Health, Meghaninagar, Ahmedabad-380016, Gujarat, India. Experience: Around 25 years experience in the related field. Dr. Syed Published 30 articles (14 national and 16 international). Field of Specialization: Pesticides Biochemistry and toxicology, Residues analysis by GC, Metal and solvent toxicity, Endocrinology and reproductive toxicity, Radio Immunoassay (RIA) for Hormones & neurotransmitters estimation, Ionchromatography (Dionex IC 2500) for trace and heavy metals analysis. Current specialization: Metals/ pesticides toxicity and metabolism RIA, biochemical/pathological analysis, Ion-chromatography.
Background information: Drinking water contamination with hexavalent chromium (Cr6+) either by natural or anthropogenic sources is an emerging global health problem. This issue got much impetus when Public Health Goal (PHG) proposed a maximum contamination limit (MCL) as low as 0.02 μg/l for Cr6+ against the current MCL for total chromium (50 μg/l, WHO). At present, Cr 6+ is an unregulated chemical; therefore, its monitoring and regulation deserve special attention. Materials and Methods: Ahmadabad city is the sixth largest city of India with a population more than 6.3 million. A general survey covering all the specified zones of Ahmedabad was carried out to examine naturally occurring Cr6+ in drinking water, obtained from Ahmedabad Municipal Corporation (AMC) and personal bore water supply. A total number of 415 drinking water samples (AMC, N=125: personal bore water, N=290) were analyzed for Cr6+ by ion chromatography employing US EPA method 218.6. Results: A wide variation in the level of Cr6+ in drinking water was observed in bore water samples. The average value of Cr6+ was registered to be 14.57 μg/l (range 0.0 - 322.64 μg/l) with a median value of 6.39 μg/l. Cr6+ was not detected in about 19% of the bore well water samples (detection limit 0.3 ppb). On the contrary, AMC water supply had a considerably lower level of Cr 6+ (average 3.58μg/l, range 0.0 – 13.78 μg/l, median 2.58 μg/l) and it was not detected in 39.5% of the water samples. Seven bore water samples exceeded the maximum prescribed limit of WHO (50 μg/l). Relatively higher levels of Cr6+ in water samples were detected in the south and east zones of the city associated with industrial area as compared to non-industrial area. Discussion: Data obtained in the present study are several hundreds to thousands-fold high than the suggested PHG (0.02μg/l) level of Cr 6+ as MCL. As the regulation of Cr6+ in drinking water is lacking at present, there have been great uncertainties of the risk assessment due to Cr6+ exposure. The general population ingesting Cr6+-contaminated drinking water might be at risk for developing chromium-induced health effects. Conclusion: Cr6+ and its compounds are known carcinogens and need tight regulation. Data produced in this study might be useful for establishing revised MCL for Cr6+, which is lacking at present. Keywords: Hexavalent chromium, Cr6+, PHG, ionchromatography, drinking water.