201. Influences of dissolved humic acid on Zn bioavailability and its consequences for thyroid toxicity.
- Author
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Li, Jian, Liu, Yun, Zuo, Rui, Teng, Yanguo, Ai, Yang, and Yang, Jie
- Subjects
HUMIC acid analysis ,ZINC compounds ,BIOAVAILABILITY ,THYROID gland physiology ,VOLTAMMETRY ,TOXICITY testing - Abstract
Abstract This study aimed to investigate the effect of dissolved humic acid (dHA) on Zn bioavailability and the subsequent influence on the Zn-induced thyroid toxicity. Zn toxicity was assessed using a yeast bioassay in the presence and absence of dHA. With increasing concentration of dHA, the toxic effects decreased, and the free Zn concentrations detected by the anodic stripping voltammetry (ASV) method also decreased. The high correlation (R = 0.92, p < 0.001) between toxic effects and free Zn concentrations indicated that Zn thyroid toxicity largely comes from the free Zn fraction. Water samples from the Qing River in Beijing were also assayed for thyroid toxicity. The results revealed that the metals might contribute to the toxicity. The known thyroid hormone-disrupting metals, namely, Zn, Cd and Hg, were analyzed. The cause-effect relationship between the observed thyroid toxicity and free Zn concentrations as well as their dose-effect relationships were examined. Our results showed that Zn might be the major contributor to the observed thyroid toxicity caused by metals. These results suggest that the ASV method and the identified major contributor (Zn) may be used in lieu of conventional environmental analyses to follow the progression of a risk assessment or remediation strategy. Graphical abstract fx1 Highlights • Dissolved humic acid decreased Zn thyroid toxicity as evaluated by yeast bioassay. • The ASV method was used for detecting free Zn concentration. • The Zn–dHA mixture toxicity comes mainly from free Zn. • The combined ASV method and yeast bioassay might be used for identifying the contributor(s) of thyroid toxicity. • The major metal contributor in the Qing River might be Zn. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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