In the present study, we have investigated the hydrolysis of iprodione and developed its analytical method. In purified water, degradation of iprodione and formation of its degradation product was observed in the timedependent manner. After 1 week, approximately 70% of iprodione was degraded and transformed to its degradation product. Further, degradation product of iprodione was stable at least 15 days in purified water. Therefore, it is preferable to measure not only iprodione, but also degradation product of iprodione in tap water. Further, we have conducted a validation test, in order to confirm the validity of the analytical methods by GC-MS and LC-MS/MS. Recovery tests of iprodione and its degradation product spiked into purified and drinking water were performed in two set points, which are 1/10 and 1/100 of target values of iprodione in Japan. The results by GC-MS analysis were not satisfied with the criteria in the guideline for validation of testing method in drinking water, which has been notified by the Ministry of Health, Labour and Welfare, Japan. Accuracy, repeatability, and intermediate precision for iprodione and degradation product of iprodione obtained by LC-MS/MS analysis were satisfied with the criteria. Therefore, we concluded that the LC-MS/MS analytical method developed in the present study is valid for the analysis of iprodione and its degradation product in drinking water.

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We surveyed chlorine-resistant protozoa in 137 samples of sewage from 22 locations in Hyogo prefecture and Cryptosporidium and Giardia were detected microscopically. From FY2018 to FY2019 we conducted surveys selecting mainly in rural areas or residential areas that are not affected by livestock. In one area where drinking water was taken from a shallow well which is likely contaminated by surface water and supplied only by chlorination, Cryptosporidium was found twice. On the other hand, Giardia has a high background, probably due to infection caused by unknown factors, and its relationship with the water treatment plant was not detected.

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