Evaluation of the oxidative stress in liver of crucian carp (Carassius auratus) exposed to 3,4,4'-tri-CDE, 2-MeO-3',4,4'-tri-CDE, and 2-HO-3',4,4'-tri-CDE.

Polychlorinated diphenyl ethers (PCDEs) are a class of potential persistent organic contaminants, which have been widely detected in aquatic environment. In the present study, the effects of 3,4,4'-tri-CDE and its two possible metabolites (2-MeO-3',4,4'-tri-CDE and 2-HO-3',4,4'-tri-CDE) on oxidative stress biomarkers in liver of Carassius auratus were evaluated. The fish were treated with these three compounds at different doses (0.1, 1, and 10 µg/L) via semi-static water exposure. The liver samples were individually taken at 3, 7, and 21 days for analysis of oxidative stress indicators, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), and malondialdehyde (MDA). Compare to the control group, the hepatic antioxidant enzyme activity and GSH contents showed significant decreases (p < 0.05) at high-dose treatment (10 µg/L) and prolonged exposure time (21 days) in most of the toxicant-treated groups, indicating the occurrence of oxidative stress in fish liver. However, no consistent trend of the variations of antioxidant parameters was observed at low doses (0.1 and 1 µg/L). Meanwhile, the lipid peroxidation was significantly induced with extending exposure time and increasing dose. In addition, the toxicity order of three compounds was discussed using the integrated biomarker response (IBR) index. Notably, 2-HO-3',4,4'-tri-CDE was indicated to cause the most severe hepatic oxidative stress.

Polychlorinated diphenyl ethers (PCDEs) in surface sediments, suspended particulate matter (SPM) and surface water of Chaohu Lake, China.

Polychlorinated diphenyl ethers (PCDEs) are typical halogenated aromatic pollutants that have shown various toxicological effects on organisms. However, the contamination status of PCDEs in the fresh water lakes of China remains poorly researched. In this study, the levels of 15 congeners of PCDEs in the sediments, suspended particulate matter (SPM) and water of Chaohu Lake were determined. The results showed that the ranges of concentrations of total PCDEs (ΣPCDEs) in the sediment, SPM and water were 0.279 ng g-1 dry weight (d.w.)-2.474 ng g-1 d.w., 0.331 ng g-1 d.w.-2.013 ng g-1 d.w. and 0.351 ng L-1-2.021 ng L-1, respectively. The most abundant congeners found in sediments, SPM and water were 3,3',4,4'-tetra-CDE, deca-CDE and 2,4,6-tri-CDE, with average contributive ratios of 17.36%, 15.48% and 20.63%, respectively. The medium and higher chlorinated PCDEs (e.g., penta- and deca-CDEs) were the dominant congeners in sediments and SPM. The percentages of lower chlorinated PCDEs (e.g., tri-CDEs) in the water were higher than those in the sediments. The combined input of ΣPCDEs from the eight main tributaries to Chaohu Lake was estimated at 6.94 kg y-1. Strong linear correlations between the concentrations of ΣPCDEs and organic carbon (OC) contents in three type samples from Chaohu Lake suggested OC could influence the distribution of PCDEs in Chaohu Lake substantially. In addition, the calculated average organic carbon normalized partition coefficients (logKoc) of 15 PCDEs between water and SPM were in the range of 4.55-5.45 mL g-1. This study confirmed that Chaohu Lake is contaminated by PCDEs.

QSPR modeling of the logKow and logKoc of polymethoxylated, polyhydroxylated diphenyl ethers and methoxylated-, hydroxylated-polychlorinated diphenyl ethers.

In the present study, the structural parameters of 209 types of polymethoxylated diphenyl ethers (PMeODEs), 209 types of polyhydroxylated diphenyl ethers (PHODEs), seven types of methoxylated-polychlorinated diphenyl ethers (MeO-PCDEs) and seven types of hydroxylated-polychlorinated diphenyl ethers (HO-PCDEs) were calculated using the Gaussian 09 program at the B3LYP/6-311G** level. Using structural and positional parameters as descriptors, quantitative structure-property relationships (QSPR) models for the prediction of n-octanol/water partition coefficient (logKow) and soil sorption coefficient normalized to organic carbon (logKoc) were established and verified. The position parameters N2(6), N3(5) and N4 were the main positional factors influencing logKow and logKoc of PMeODEs and PHODEs. The molecular polarizability α was entered into the QSPR models of the logKow and logKoc of PMeODEs, PHODEs and MeO/HO-PCDEs, indicating that the molecular volume could influence the two environment-related properties of DEs significantly. All of the established QSPR models showed good goodness-of-fit, robustness, and predictive ability. The two models for all of the tested DEs are slightly inferior compared with the models for only a class of compounds. In addition, application domain analysis indicated that the models reliably predicted the logKow and logKoc of the mon- to hexa-DEs.

Toxicity evaluation of 4,4'-di-CDPS and 4,4'-di-CDE on green algae Scenedesmus obliquus: growth inhibition, change in pigment content, and oxidative stress.

Polychlorinated diphenyl sulfides and polychlorinated diphenyl ethers are two types of dioxin-like pollutants, which are prevalent in aquatic environments. However, to date, limited information is available regarding their toxicity to green algae. In this study, growth inhibition, effect on pigment content, and oxidative stress potentials of 4,4'-di-CDPS and 4,4'-di-CDE on green algae Scenedesmus obliquus were investigated. The results indicate that the EC50 values of 4,4'-di-CDPS after 24, 48, 72, and 96 h of exposure were 1.736, 1.172, 0.994, and 0.820 mg/L, while the corresponding values for 4,4'-di-CDE were 0.697, 1.087, 0.833, and 0.327 mg/L. As compared to the control group, most of the measured pigment content in algal cells significantly decreased after 96-h exposure to these two chemicals, suggesting their suppressive capability on the photosynthesis process in algal cells. Additionally, oxidative stress occurred as demonstrated by the significantly inhibited activities of the antioxidant enzymes (total superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GPx)), and high increases in malondialdehyde (MDA) content in all 4,4'-di-CDE-treated groups and some moderate-dose and high-dose treatments with 4,4'-di-CDPS. Acute toxicity tests and biochemical analysis showed that 4,4'-di-CDE was more toxic than 4,4'-di-CDPS on S. obliquus.