Recent topics on chemicals in drinking water

<p>Per- and polyfluoroalkyl compounds (PFAS), pesticides, and haloacetic acids were introduced as recent topics on chemicals in drinking water. As for PFAS, PFOS (perfluorooctanesulfonic acid) and PFOA (perfluorooctanoic acid) were selected as complementary items for water quality management in 2020, after which time monitoring data for these substances in the water supply system across Japan have been tallied in the Statistics on Water Supply by the Japan Water Works Association. However, as the number of these monitoring data is smaller than those for other items, more monitoring points for PFOS and PFOA are needed. Drinking water treatment processes have been applied for the purpose of PFAS removal in overseas countries. However, most of these processes, which involve activated carbon treatment, which has been applied in many cases, are applied for the purpose of removal of the substances other than PFAS in Japan. Therefore, it is important to study the operating conditions for PFAS removal at drinking water treatment plants, including cost considerations. Since there are many types of pesticides and the timing of their use depends upon the application, it is necessary to set the timing and frequency of the measurement of pesticides for their detection. However, there are currently cases where the monitoring plans for pesticides are inappropriate (e.g., all pesticides complementary items for water quality management are measured once a year at many water supply systems). The types and guideline values of pesticides that have been selected as complementary items for water quality management are continuously revised under a rolling revision system of drinking water quality regulation. As the detection of some pesticides that have been newly added as complementary items (e.g., tefuryltrione and ipfencarbazone) has been reported, countermeasures for these new pesticides are also required. Three chlorinated haloacetic acids have been selected as standard items in drinking water, and trichloroacetic acid, in particular, became one of the items most likely to exceed its standard value after a significant tightening of the value in 2015. Among the brominated haloacetic acids selected as items for further study, proposed guideline values for bromochloroacetic acid and bromodichloroacetic acid were introduced, and the acids were found in tap water at an excess of 50% over their proposed guideline values. Thus, it is considered that water quality management involving brominated species is needed for haloacetic acids.</p>