1,2,3-benzotriazole adversely affects early-life stage of Oryzias latipes

Abstract

1,2,3-benzotriazole (BT) is used in large amounts around the world and is one of the substances derived from household chemicals that are of concern for risk when discharged to aquatic environments. Therefore, several studies have been conducted on the aquatic toxicity effects of BT, but the chronic impact assessment studies to evaluate the developmental effects on the early-life stage of fish are insufficient. In this study, the acute toxicity test and subchronic toxicity test (fish, early-life stage toxicity test, ELS test) using embryos of Japanese medaka (Oryzias latipes) were performed to evaluate the acute toxicity, developmental toxicity, growth (indicated by total length and weight at the end of the test), and histopathological effect of BT. In the short-term toxicity test on embryo and sac-fry stage, toxicity value was calculated to be 41 mg/L (NOEC). Based on this value, the exposure concentration of the ELS test was determined as 0.04, 0.4, 4 and 40 mg/L, and total exposure duration was 42 days. At the highest concentration group (40 mg/L), failure of swim bladder inflation and decrease of survival and size (total length and weight) were observed. Moreover, in the histopathological analysis, abnormal findings were detected in swim bladders from the 40 mg/L group such as inflammation and tumor changes. On the other hands, condition index (weight-length relationships, CI) was statistically significantly lower in all exposed groups compared to the control group. NOEC for the survival of BT was calculated to be 4 mg/L. LOEC for CI was 0.04 mg/L, which means BT inhibited weight gain relative to its length on larvae of medaka.

Keywords: Benzotriazole; Condition index; Early-life stage; Fish; Oryzias latipes; Swim bladder.