Dianchi Fish Typical Environmental Endocrine Disruptors Bioconcentration And Toxic Effects

Endocrine disrupting chemicals (EDCs) are defined as exogenous agents that interfere with the production, release, transport, metabolism, binding, action, or elimination of natural hormones in the body. These compounds are responsible for the maintenance of homeostasis and the regulation of developmental processes. EDCs may disturb the function of endocrine system in human and wildlife and consequently cause adverse effects on development, reproduction, immune and nervous system of organism. The adverse effects, such as hermaphrodism (male and female gonads in a single individual) and feminization in wild fish, and breast, prostate and testicular cancer in human, have been widely reported. EDCs, particularly steroids and phenols, have attracted a great deal of scientific and public attention worldwide due to their potential adverse effects on the normal reproduction and development of environmentally exposed organisms.Currently, steroids and phenols have been detected in rivers and lakes all over the world. Sources, distribution characteristics and environmental fate of steroids and phenols in water and sediment were also estimated. However, their occurrence in fish and other aquatic organisms has been reported in only a limited number of studies and their bioaccumulation has not been well studied. The low levels of EDCs and complex matrix (contain a number of potentially interfering compounds) make measurement and monitoring of these contaminants in biological samples challenging. Thus, the development of an analytical method for the accurate determination of EDCs in biological samples is of crucial importance. In addition, toxicity studies are popular in the use of ideal experimental fish, such as zebrafish (Danio rerio), medaka (Oryzias latipes) and fathead minnow (Pimephales spromelas). Most toxicity data available are restricted to acute toxicity test or short-term exposure experiment in laboratory. Therefore, the lack of long-term exposure data often limits their application in the assessment of biological effects and environmental risk of EDCs in aquatic environment.In this study, typical representatives of steroidal and phenolic EDCs, including estrone (El),17β-estradiol (E2),17a-ethynylestradiol (EE2), estriol (E3),4-tert-octylphenol (4-t-OP),4-cumylphenol (4-CP),4-nonylphenol (4-NP) and bisphenol A (BPA), are collectively selected as target compounds, which have been found in water samples collected from Dianchi Lake in our previous studies. The objective of this study was to investigate the bioaccumulation characteristic and tissue distribution of steroidal and phenolic EDCs in wild fish collected from Dianchi Lake, including crucian carp(Carassius auratus), carp (Cyprinus carpio) and silvery minnow (Anabarilius alburnops), and to estimate the effects of steroidal and phenolic EDCs on high-back crucian carp(Carassius auratus) by exposure experiment in WWTP effluents, Dianchi Lake and laboratory. Biological effects and environmental risks of EDCs on fish in Dianchi lake were also comprehensively examined by combining the experiments of environmental analytical chemistry and toxicological exposure. The research results would provide scientific basis for making strategies and measures of EDCs in Dianchi catchment, which has remarkable significances in theory, social, environmental health and engineering application.(1) An improved method was developed for the simultaneous determination of eight steroidal and phenolic EDCs in biological samples. The proposed method were consisted of sample collection, microwave-assisted extraction (MAE), automated gel permeation chromatography (GPC), solid phase extraction (SPE), derivatization and gas chromatography-mass spectrometry (GC-MS) analysis. The optimal extraction and cleanup procedures were investigated using MAE, GPC and SPE. Experimental results indicated that the most efficient extraction was achieved by using MAE with methanol as solvent at an extraction temperature of110℃for20min. The cleanup of extracts was carried out by GPC on a Biobeads S-X3column with cyclohexane/ethyl acetate (1:1, v/v) as mobile phase. Target compounds were eluted in the fraction from7-14min retention time. Moreover, the cleanest extracts were obtained by solid phase extraction with C-18cartridges after the elution with15mL ethyl acetate. The method was validated by spiked samples which showed good recovery and reproducibility. The overall recoveries ranged between55.1%and100.6%, with relative standard deviations (RSD) of2.3-12.7%for the entire procedure. Method detection limits (MDL) ranged from0.3to0.7ng g-1dry weight (dw). Performance of the method was demonstrated by its application on tissues from fish exposed to high concentration of EDCs in the laboratory. The developed method is a promising approach for the analysis of steroid and phenolic endocrine disrupting chemicals in various biological samples.(2) The distribution and bioaccumulation of steroidal and phenolic EDCs were studied in various tissues of wild fish species from Dianchi Lake, China. In muscle tissue, phenols (4-t-OP,4-CP,4-NP and BPA) were detected in fish from each sampling site, with maximal concentrations of4.6,4.4,18.9and83.5ng/g dw, respectively. Steroids were found at lower levels (<11.3ng/g dw) and less frequently in muscle samples. An interspecies difference in concentrations was evident due to their feeding preference, general behavior and trophic level. Indeed, it was found at the highest levels in silvery minnow but at levels2-3times lower in crucian carp, carp showed intermediate levels. Moreover, the concentrations of steroids and phenols in the gill, liver, and muscle were very variable. The highest concentrations were found in the liver, followed by those in the gill and the lowest in muscle. The field BCF values of phenols in the18to97range were calculated in different fish species. The estimated concentrations of steroids in water were in the range of4.4-18.0ng/L, which were in the proper range compared with those reported by other researchers. These results showed that steroidal and phenolic EDCs were likely ubiquitous contaminants in wild fish. In addition, muscle and tissue concentrations could be a valid means by which to assess the contamination of EDCs in surface water.(3) Compared with fish controls caged in Dianchi Lake, the biological effects and bioaccumulation of steroidal and phenolic EDCs were assessed in high-back crucian carp exposed to WWTP effluents. The results indicated that high-back crucian carp readily accumulated steroidal and phenolic EDCs from WWTP effluents, resulting in the enhanced synthesis of vitellogenin (Vtg), the inhibition of gonad growth and the increase of liver metabolism. Some of the differences in biological response appeared to relate to differences in EDCs uptake and metabolism. Therefore, the presence of steroidal and phenolic EDCs in muscle samples of high-back crucian carp could be used as an effective biomarker of exposure to WWTP effluents, considering the capacity of bioaccumulation of this species.(4) In acute toxicity test, the96h half-lethal concentrations (LC50) of E2and EE2to juvenile high-back crucian carp were0.403mg/L and0.149mg/L, respectively. The biological bioaccumulation and toxicological effects of E2and EE2were assessed in high-back crucian carp exposed to low concentrations of E2and EE2(single and binary mixture exposure) in flow-through exposure system for16months. The results showed that high-back crucian carp readily accumulated E2and EE2from single and binary mixture exposure group, resulting in the inhibition of growth status and gonad growth, the increase of Vtg levels and liver metabolism. High-back crucian carp were generally more sensitive to EE2than E2exposure. Moreover, the biological effects of binary mixture of E2and EE2at the low concentration were more potent than that of individual compounds when GSI, HSI and Vtg were used as endpoint. The results of acute toxicity test and long-term exposure experiment in laboratory indicated that high-back crucian carp were sensitive to typical EDCs and may be chosen as potential model species in field and laboratory studies.