Abstract
Perchlorate concentrations in raw and tap water in Osaka, Japan, were determined by IC-MS/MS. The concentrations of perchlorate in raw water and tap water were in the ranges from <0.015 to 0.48 μg/L and from <0.015 to 0.82 μg/L, respectively. Except for only a few cases, the perchlorate concentration in each tap water sample was at nearly equivalent level to that in the corresponding raw water. The results indicate that perchlorate in raw water was not removed effectively by the ordinary water treatment methods such as ozonation, granular activated carbon adsorption, rapid and slow sand filtrations. On the other hand, perchlorate was found to be contained in sodium hypochlorite solutions, used in the chlorination process, at wide concentration range between 4.9 and 5900 μg/L. In the case using disinfectant with the highest perchlorate content, the significant increase in perchlorate concentration in tap water was observed, compared to that in raw water. However, when 2 L of tap water was ingested every day, the corresponding perchlorate intake was estimated to be at most 1.8 μg/day from the observed perchlorate concentrations in tap water samples. This value was sufficiently lower than the calculated daily intake for a person weighing 50 kg from reference dose value of perchlorate. Therefore, the health risk to humans from perchlorate in tap water in Osaka, Japan, is very low.
