Schistosomiasis has prevailed in some areas of China for a long time. Chinese technical sodium pentachlorophenate (Na-PCP) has been used to control the spread of snail-borne schistosomiasis since the 1960s. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), impurities contained in the Na-PCP, enter the soil and may accumulate in the food chain. In order to evaluate their potentially harmful effects on local residents, 50 breast milk samples and 20 blood samples were collected in 2004 from residents in the Dongting Lake area, one of China's known schistosomiasis areas. Levels of 17 PCDD/F congeners were measured in all samples, and DNA damage was simultaneously assessed in blood samples. The PCDD/F congener distribution patterns in human tissue samples from the Dongting Lake area were similar to those in Na-PCP, and the octachlorodibenzodioxin (OCDD) congener was predominant in all samples. We also had a primary investigation that the breast milk WHO-TEQ associated with some factors such as: age, dietary habit, body mass index (BMI) and the total menses times. In blood samples, the samples with higher OCDD level had higher DDS (DNA damage score) values than those samples with low OCDD level, which indicated that the higher DNA damage value in general population might be caused directly or indirectly by PCDD/Fs. The results also indicated that the WHO-TEQ values in blood were associated with age (r=0.6, p=0.007).
[Show abstract][Hide abstract] ABSTRACT: A novel horseradish peroxidase (HRP)-catalyzed H₂O₂ process in the presence of reduced nicotinamide adenine dinucleotide (NADH) was applied to remove aqueous pentachlorophenol (PCP). Parameters (pH, H₂O₂ concentration, HRP activity and NADH dosage) on PCP removal were investigated. It was found that initial 0.05mM PCP was removed by 98% in HRP-NADH-H₂O₂ system at pH 5.0 and 30°C for 1h. Addition of O₂ in HRP-NADH-H₂O₂ system enhanced the removal rate of PCP due to promoting hydroxyl radicals (.OH) and superoxide anion radical (.O₂⁻) generation, which were confirmed by electron paramagnetic resonance (EPR)-spin trapping method. PCP removal efficiency decreased when .O₂⁻ and H₂O₂ were scavenged by superoxide dismutase and catalase in HRP-NADH-O₂ system, indicating that .OH/.O₂⁻ played a great role in the degradation of PCP. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that octachlorinated dibenzodioxin (OCDD) in residual solution was reduced after treated by the HRP-NADH-O₂ process, resulting in lower toxicity of treated solution than conventional enzymatic process. Two enzymatic-catalysis pathways were proposed for PCP removal in HRP-NADH-H₂O₂/O₂ system: (i) OH/.O₂⁻ free radical oxidation (ii) conventional phenoxy polymerization.
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