We review the current challenges in the ecological risk assessment of ethylenediaminetetraacetic acid (EDTA) and cationic surfactants under Japan’s Chemical Substances Control Law. The complexity of EDTA toxicity assessment arises from its chelating properties, which influence metal bioavailability and ecological toxicity, making conventional assessment methods inadequate. Meanwhile, the toxicity of cationic surfactants is significantly affected by environmental factors, particularly organic matter content and water quality parameters. These variations pose substantial difficulties in achieving reliable toxicity assessments. While the Biotic Ligand Model (BLM) has been applied to address similar challenges in metal toxicity assessment, its effectiveness in evaluating EDTA and cationic surfactants has yet to be fully demonstrated. This paper examines existing evaluation methods, identifies their limitations, and proposes potential approaches for improving the reliability of risk assessments for these difficult-to-test substances.

Sertraline is an antidepressant belonging to the class of selective serotonin reuptake inhibitors. It is frequently detected in aquatic environment because it cannot be completely degraded in the sewage plants. The effects and mechanisms of sertraline in mammals are well understood. However, its chronic effects in fish have been poorly evaluated. In this study, Japanese medaka (Oryzias latipes) was exposed to sertraline for 14 days, and the effects of sertraline on the fish brain were evaluated using a metabolomics approach. Exposure to 115 µg/L sertraline increased glutamate levels; however, this effect was suggested to be suppressed by several amino acids after 14 days of exposure. The effects in fish exposed to sertraline are unlikely to occur in actual aquatic environments.

This is the report of CERI award in 2023. We evaluated the long-term effects of chemicals, i.e. carbamate pesticides on the aquatic organisms (cladocerans and chironomids), which contributes to receiving the award. Several chemicals, e.g. pesticides transiently discharge into the river or lake because the chemicals rapidly flow into river by heavy rainfall. Considering the realistic exposure to chemicals, we performed the several multigenerational studies on aquatic organisms under the two conditions; 1) transient exposure (48 h) of the test organisms to the model chemical (insecticides or a pharmaceutical); 2) continuous exposure to the model chemical. In both of cases, a part of species acquired chemical tolerance to the test substance. We then elucidated the several mechanisms of chemical tolerance and the fitness costs. Here, I summarize our findings in this review paper. Additionally, to obtain the information on the multigenerational alteration in chemical sensitivity, I made literature search of the research papers on the multigenerational studies for cladocerans and chironomids. To clarify further long-term effects of chemicals, we should connect each finding in several multigenerational study.

The co-existence of microplastics and hydrophobic organic chemicals is ubiquitous in the environment. Microplastics may act as vectors for the transmission of organic pollutants to organisms. In the present study, we co-exposed 33 adult medaka fish to a mixture of chlorobenzenes (CBs; trichlorobenzene, tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene—at 10, 10, 10, and 8 µg/L, respectively) and two different sizes of polystyrene microplastics (PS-MP)—10-µm PS-MP at 0.1 mg/L and 45-µm PS-MP at 0.45 mg/L. We exposed the fish to CBs, CB10MP (CBs+10-µm PS-MP), and CB45MP (CBs+45-µm PS-MP) for 7 days followed by 3 days for excretion. We measured the concentrations of CBs and PS-MP in the fish on days 7, 8, 9, and 10 and in the water on days 5, 6, and 7. Our results clearly indicated that there was no increase in the concentration of CBs in the medaka co-exposed to MPs and either size of PS-MP. This result might have been due to the sorption of Tri- and TetCBs to PS-MP and little or no desorption in the gut. Our study revealed the absence of a vector effect of PS-MP on the bioaccumulation of CBs in medaka.

The ecotoxicity of copper (Cu) in the marine environment is of increasing concern. An understanding of benefits and risks in the use of Cu in Japanese coastal areas, particularly information of Cu effects on native copper-sensitive organisms is urgently required. In this study, we conducted ecotoxicity tests on the sensitive early life stages of local abalone (Haliotis discus hannai) using seawater collected from their natural habitat in Miyagi Prefecture, Japan. The no observed-effect concentration (NOEC), 10% effect concentration (EC10), and 50% effect concentration (EC₅₀) for Cu were determined to be 3.5, 5.8, and 8.6 µg/L, respectively. To account for bioavailability, we calculated the EC10 using the correction formula for dissolved organic carbon (DOC) provided in the Voluntary Risk Assessment Report of the European Chemical Agency, using literature values for DOC specific to the Japanese coastal area. As a result, the EC10 ranged from 3.2 to 11.7 µg/L. These results are important for policy makers to establish more realistic Cu water quality standards that take into account the effects on key species and the diverse characteristics of different regions within Japanese coastal areas.