『保健医療科学』 2023 第72巻 第3号 p.203 －211（2023年8月）
特集：身の回りに潜む健康リスクと我が国の安全管理への取組
＜総説＞
水道における化学物質に関する最近の話題
小坂浩司
国立保健医療科学院生活環境研究部
Recent topics on chemicals in drinking water
KOSAKA Koji
Department of Environmental Health, National Institute of Public Health
抄録
水道における化学物質の最近の話題として，ペルフルオロ及びポリフルオロアルキル化合物（PFAS），農薬類，ハロ酢酸を採り上げた．PFASは，2020 年にペルフルオロオクタンスルホン酸（PFOS）及びペルフルオロオクタン酸（PFOA）が水質管理目標設定項目に格上げされ，（公社）日本水道協会による水道統計で全国の水道での調査結果が集計されるようになった．しかし，調査地点数は他の項目に比べて少なく，より多くの地点での調査が必要であると考えられた．海外では，PFAS処理を目的に適用されている浄水プロセスが報告されているが，国内では，それらプロセスは，適用事例が多い活性炭処理を含めて，ほとんどの場合，PFAS以外の項目の除去を目的に適用されている．このため，浄水場でPFAS処理に適用した場合の運転条件について，コスト面も含めた検討が重要である．農薬類は，種類が多く，用途により使用時期等が異なるため，検出できるように測定の時期や回数を設定する必要があるが，現状は，全項目を年間 1 回測定するところが多い等，測定計画が適切に設定されていない場合がある．逐次改正方式により，水質管理目標設定項目に指定されている農薬類の種類や目標値は継続的に見直しが行われている．テフリルトリオン，イプフェンカルバゾン等，新規に追加された農薬類の検出が報告されており，これら新たな農薬類についての対応も求められている．3 種の塩素化ハロ酢酸は水質基準項目に指定されているが，特にトリクロロ酢酸は，2015 年に基準値が大幅に強化された後は，基準値を超過しやすい物質の一つとなった．要検討項目の臭素化ハロ酢酸のうち，ブロモクロロ酢酸とブロモジクロロ酢酸は目標値案が示され，給水栓中でその 50%を超える値が報告されており，臭素化体も含めた管理が望まれる．
キーワード：PFAS，PFOS，PFOA，農薬類，ハロ酢酸
Abstract
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.
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keywords: PFAS, PFOS, PFOA, pesticides, haloacetic acids