PCP-Naのコイに対する毒性と体サイズ依存性の検証—過去の毒性データを農薬再評価制度で使用できるか？—

抄録

Since the Agricultural Chemicals Regulation law in Japan has been revised in 2019, we should conduct the ecotoxicology tests for the pesticide registration under the rules in the OECD guideline tests. However, there were several differences between the Japanese and OECD guideline tests, such as the body size of test fish in the fish acute toxicity test. For instance, recommended body size in Cyprinus carpio before the revision of Japanese guideline was 2–6 cm (total length), whereas that in the OECD test guideline (OECD TG) 203 is 2–4 cm. To confirm the toxicity in the different body sized C. carpio (total length: 3–6 cm) to Pentachlorophenol sodium (PCP-Na), we conducted the fish acute toxicity tests according to the OECD TG 203. The median lethal concentrations (96 h-LC₅₀ values) (0.12–0.26 mg/L) in all the test groups were comparable to each other. However, the median lethal time (LT₅₀ value) (as a sub-parameter in this research) was correlated with the fish body size, suggesting that this parameter is easily affected by the small difference in body size. Considering the test reproducibility, it may be difficult to use the LT₅₀ value for the guideline test. In summary, the previous experimental data using 3–6 cm test fish may be applied to the revised guideline test in Japan.