Toxic Effects of Triclosan and Triclocarban on Gobiocypris rarus at Various Developmental Stages during Long-term Exposure.

Triclosan (TCS) and triclocarban (TCC) are two highly effective broad-spectrum antimicrobial agents having embryo toxicity, endocrine disruption, and reproductive toxicity. These two chemicals are presently emerging pollutants of wide concerns and may cause cancer, DNA damage, and adverse pregnancy outcomes. In 2016, the US Food and Drug Administration (US FDA) has banned market entry of the over-the-counter antibacterial bath products containing antibacterial agents such as TCS and TCC. In China, however, TCS and TCC are still allowed to be used in a limited quantity as quasi-preservatives for cosmetics, and are not restricted for soap products. As emerging exogenous chemical pollutants, TCS and TCC can enter the natural environment with domestic wastewater and pose potential threats to local aquatic lives, ecological security and human health. In order to investigate the toxic effects of TCS and TCC on the long-term exposure and four different developmental stages (i. e., embryo, yolk sac absorption, larval, and juvenile stages) of the Chinese native fish species of Gobiocypris rarus (GR), the fertilized eggs of GR were exposed to TCS and TCC until 60 days post hatching (60 dph) in this study. The results showed that TCS and TCC in the ranges of 6.25 ~ 100 µg ⋅ L^-1 and 0.938 ~ 15 µg ⋅ L^-1, respectively, had no significant toxic effects on the embryo hatchability of GR. In the larval stage, the no observed effect concentration (NOEC) of the 30 dph survival rate in the exposure groups of 6.25 ~ 100 µg ⋅ L^-1 TCS and 0.938 ~ 15 µg ⋅ L^-1 TCC were 100 µg ⋅ L^-1 and 0.938 µg ⋅ L^-1, respectively. According to the national standards of China, the hazards of TCC to the aquatic environment were classified as long-term chronic category 1. In contrast, it is impossible to make a clear judgment for TCS because its maximum testing concentration did not reach 1 mg ⋅L^-1, but the hazards of TCS to the aquatic environment can be judged as the non-long-term chronic category 1. At the juvenile stage, TCS (6.25 ~ 100 µg ⋅ L^-1) and TCC (0.938 ~ 15 µg ⋅ L^-1) could induce vitellogenin in both females and males of GR, but did not affect sexual differentiation. During the postembryonic development, TCS of 6.25 ~ 100 µg ⋅ L^-1 could significantly affect the fish body weight, which gradually decreased with increasing TCS concentration, indicating that TCS could inhibit the body weight of GR. TCC of 0.938 ~ 15 µg ⋅ L^-1 had no significant effect on the fish body weight and body length. In addition, it was found that the toxic effects on the different developmental stages of GR were different. The tolerance of GR at embryonic stage was significantly higher than that at postembryonic development stage, while the tolerance at yolk sac absorption stage and larvae stage was lower than that at the juvenile stage. Therefore, when more of these life stages are included in a test, more toxicity endpoints can be obtained by fewer test animals. Moreover, the toxic effects of different life stages in the tests are all from the same batch of the test animals, making the test results of different life stages more comparable. [ABSTRACT FROM AUTHOR]