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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

In the context of a substance evaluation process a study on the sexual development of fish was requested (OECD 234). The first stage of this studies covers the endpoints of an early life stage test which is normally conducted as long-term fish study. In course of the OECD 234 study the NOEC for post hatch survival was calculated and is used in the assessment to cover the long-term effects of 1H-Benzotriazole on fish.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Dose descriptor:
Effect concentration:
1.07 mg/L

Additional information

No additional information on marine fish available.

Long-term toxicity to fish was investigated in an OECD 234 guideline study exposing D. rerio for 63 days to different concentrations on 1H-Benzotriazole. In the study no substance-related indications on endocrine disrupting properties were observed. Based on the findings a NOEC for post hatch survival and growth was calculated.

Further information on long-term toxicity is available in the public domain:

Liang et at (2016) investigated potential neurotoxic effects of 1H-Benzotriazole on the brain of female Chinese rare minnows. After 28-days exposure period with 0.05, 0.5 and 5 mg/L modulations in the expression of different proteins and mRNA were measured. Based on these findings Liang proposed potential pathways for neurotoxicity of the substance. A dose-effect relation is not clear. In addition, information on physiological effects on the fishes is not stated in the publication. Therefore, the relevance of the findings on individual fish cannot be evaluated.

Zeng et al. (2016) reported on the toxic potential of 1H-Benzotriazole in rainbow trout cell lines. The substance showed a low toxicity on the cell viability (> 130 mg/L) and a low potential to induce Cytochrome P4501A.

Several available publications showed indication for potential endocrine activity of Benzotriazole in different fish species and in vitro assays.

Harris (2007) found evidence for antiestrogenic activity of Benzotriazole in vitro. In vivo testing with fathead minnows showed no effect on the vitellogenin (VTG) concentration in male fish and reduced VTG concentrations in female fish, which could be induced via non-ED mechanism. Additionally, no effect on the GSI was observed in both sexes.

In 2012 Tangtian described changes of the expression levels of different CYP proteins and VTG in medakka, which might indicate potential estrogenic activity of Benzotriazole after long-term exposure.

Liang (2014) observed hepatotoxicity and effects in the reproductive organs (degradation of ovaries and stimulation of spermatogenesis). Additionally, transcription levels of different proteins were modified and expression of vitellogenin was significantly increased.

Fent (2014) identified in vitro antiandrogenic effects only and concluded that Benzotriazole potentially may inhibit actions of the androgen receptor mediated effects in vivo, including spermatogenesis and/or male fertility.

Findings in a study (Liang, 2017) indicate a hepatotoxic effect of long-term exposure with Benzotriazole to rare minnow. Protein analysis showed effects on proteins, which are involved in xenobiotic clearance, oxidative stress response, apoptosis as well as translation. These effects on molecular level were also observable on cellular level. The liver cells from fish exposed to all treatment concentrations showed hypertrophy, nuclei pyknosis and increased vacuolization.

No developmental toxicity was observed in a study (Duan, 2017) with zebrafish embryos after exposure with 5.0 µM Benzotriazole for 4 days. However, in a second long-term testing series induction on expression levels of genes related to different mechanisms in wild type zebrafish hepatocytes was found. Additionally, imaging of livers of transgenic LiPan zebrafish showed increased average liver size. These findings might indicate hepatotoxicity in fish of Benzotriazole at relative low concentrations.

Hornung et al. (2017) investigated the reactions of different chemicals in in vitro assays to identify estrogen receptor binding mechanisms and to identify/avoid false positive findings. In the study several false findings in antagonism assays were found. In this context a new method to reduce these false positive findings was proposed. Interalia Benzotriazole was examined and showed no competing mechanism with E2.

This result might explain the positive findings by Harris which were not supported by in vivo testing.


Hornung et al (2017), Avoiding False Positives and Optimizing Identification of True Negatives in Estrogen Receptor Binding and Agonist/Antagonist Assays, Appl In Vitro Toxicol. 3(2): 163–181

Liang et al (2016), Brain quantitative proteomic responses reveal new insight of benzotriazole neurotoxicity in female Chinese rare minnow (Gobiocypris rarus), Aquatic Toxicology 181 (2016) 67–75

Zeng et al. (2016), Use of the rainbow trout cell lines, RTgill-W1 and RTL-W1 to evaluate the toxic potential of benzotriazoles, Ecotoxicology and Environmental Safety 124 (2016) 315–323