Chronic Exposure to Heavy Metals in Public Water Supply and Human Health Risk Assessment

Historic disasters resulting from heavy metals contamination of drinking water emphasize the need to assess the quality of public water supplies. Currently, millions of people in and around Bangladesh are facing chronic health risk of arsenic poisoning via drinking water. Therefore, to prevent the re-occurrence of such tragic episodes, heavy metal levels in public water supplies at Agodi-residential area of Ibadan, Nigeria were determined and human health risk assessment was done for metals whose levels were higher than the US EPA maximum contaminants level for drinking purpose. Sampling was spread from January to July, 2010 to account for variations in rainy and dry seasons. 10 public taps were sampled at 5 different times, making a total of 50 water samples collected. Metals concentrations were determined by atomic absorption spectrophotometry. The mean concentrations (mg L-1) of Cd, Co, Cr+6, Mn and Pb in the sampled water were 0.05 ± 0.02, 0.14 ± 0.02, 0.21 ± 0.07, 0.17 ± 0.02 and 0.05 ± 0.04, respectively. These values are significantly higher than the US EPA maximum contaminants level in drinking water. Health risk assessment conducted for adult and child residents, via oral and dermal routes of exposure, gave overall hazard index values of 19 and 45, respectively, while the estimated cancer risks values were 2E-03 and 9E-04, respectively. These values significantly exceed the target non-cancer hazard index of 1 and target cancer risk of 1E-06. Hence, the concentrations of the investigating metals in this public water supply are high enough to cause carcinogenic and non-carcinogenic systemic health effects to adults and children