【作者】 王伟琴；

【导师】 金永堂；

【作者基本信息】 浙江大学 ， 劳动卫生与环境卫生， 2010， 硕士

【摘要】 随着水环境富营养化状况的日益加重,蓝藻水华在我国许多大型湖泊、水库中频频暴发,不仅造成水质恶化,水环境生态平衡失调,而且蓝藻所释放的毒素严重威胁着人民群众饮用水安全。自1878年动物饮用被蓝藻污染的水而引起死亡的事件首次报道以来,世界范围内已发生多起蓝藻毒素引起水生生物、鸟类及牲畜中毒或死亡的事件,其中最令人震惊的是1998年巴西Caruaru透析中心因误将藻毒素污染的水作为透析用水,结果造成116人中毒、52人死亡。微囊藻毒素(Microcystin,MC)是蓝藻水华中最常见、毒性最大的毒素之一。研究发现其中的MCLR亚型是一种强烈的肝脏肿瘤促进剂,IARC将其列为对人类可能致癌的化学物(Group 2B)。流行病学调查提示饮用水源中的MC与人群肝癌、大肠癌发病率以及男性胃癌死亡率上升具有相关性,MC、黄曲霉毒素和乙肝病毒已成为环境中致肝癌的三大危险因素。MC促肿瘤发生的作用机制至今尚未完全阐明。大量研究表明遗传物质改变可引发致畸、致癌、致突变等“三致效应”,“大多数致癌剂都是诱变剂”,发生在体细胞遗传物质的损害可能诱发肿瘤发生,生殖细胞的基因突变或染色体畸变是可遗传变异的来源,严重损害人类的基因库。近年来关于MC的遗传毒性和远期健康效应逐渐成为研究的热点,通过煮沸或常规饮用水处理工艺均不能完全消除水中MC,而饮用水安全与群众生活息息相关,研究饮用水源水中MC对人体娇档脑镀谛вΩ哂邢质狄庖濉?浙江省地处我国东南部沿海地区,水资源总量较为丰富,但由于人口密度高,人均水资源占有量低于全国平均水平。浙江省环境监测中心2007年对省内县级以上饮用水源地中176种有机污染物的调查结果显示,多处水源水受到不同程度的MC污染,以MCLR和MCRR两种亚型为主。尤其在太湖水系饮用水源地,由于太湖蓝藻频频爆发,水源水安全受到严重威胁。利用健康风险评价模型对水源水中有机污染物经饮水途径造成的健康风险研究在我省尚属首次,系统研究饮用水源水中微囊藻毒素可能具有的遗传毒性,探讨水源水中微囊藻毒素污染与人体健康的关系,对于饮用水源地环境保护和水质改善,城乡居民饮用水安全保障,具有十分重要的理论价值和现实意义。研究目的1.对浙江省县级以上饮用水源水检出有机污染物经饮水途径造成的健康风险度大小进行评价。2.针对水源水中的两种有机污染物MCLR和MCRR,运用短期遗传毒理学试验,对其可能导致的基因突变、DNA断裂和染色体损伤效应进行检测,探讨水源水中MCLR和MCRR对遗传物质的损伤作用。研究方法1.水源水中有机污染物的健康风险评价根据浙江省环境监测中心对101个县级以上饮用水源水中176种有机污染监测数据,利用US EPA推荐的水环境健康风险评价模型对水源水中检出的有机污染物经饮水途径所造成的致癌、非致癌健康风险进行评价。2.水源水中MC的遗传毒性研究采集MC污染较为严重的水源水样,将一部分水源水以固相萃取法提取浓集其中的MC,作为MC浓集物进行遗传毒性研究;另一部分水源水用作稀释MC纯品(MCLR和MCRR)的溶剂,模拟水源水中MC的不同污染程度,作为MC稀释水样进行遗传毒性研究;针对上述两部分样品,采用单细胞凝胶电泳试验检测了MC浓集物和MC稀释水样对人外周血淋巴细胞DNA可能的损伤;采用Ames试验检测了MC浓集物和MC稀释水样诱发基因突变的能力;采用鲤鱼外周血红细胞微核试验初步观察了MC浓集物和MC稀释水样对染色体畸变效应的影响。研究结果1.本次研究中,饮用水源水检出的主要有机污染物为草甘膦、MCLR、MCRR、DEHP、DBP和咔唑,MC(包括MCLR和MCRR)和草甘膦在水源水中分布较广,检出率较高。饮用水源水中有机污染引起的总体健康风险较小,但饮用水源仍存在一定的安全隐患。2.水源水中MC浓集物可诱导人淋巴细胞DNA链断裂损伤,MC稀释水样对DNA具有一定的损伤作用,水源水中除MC以外可能还存在其他的遗传毒物。3.Ames试验中MC浓集物和MC稀释水样均未观察到明显基因突变作用,但回变率随着剂量增加存在逐渐上升趋势。4.微核试验中未观察到MC浓集物对染色体的明显损伤,MC稀释水样一定程度上可诱发鲤鱼红细胞微核率上升,具有诱导染色体畸变的效应。结论1.水源水中检出的有机污染物浓度均较低,经饮水途径造成的健康风险度较小,远低于ICRP推荐的最大可接受水平。2.水源水中MC浓集物、水源水稀释MC在一定剂量下可诱导人淋巴细胞DNA损伤,锦鲤红细胞微核率上升,存在诱发DNA断裂和染色体损伤的效应,Ames试验中未见明显致突变性。更多还原

【Abstract】 Eutrophocation has become the most important problem of water environment. Cyanobacterial blooms in lakes and reservoirs are known to occur throughout the world. These blue green alge blooms not only result in water quality deterioration, but also releases some toxins which bring severe threats to drinking water safety. Since first reported that wild animals died of drinking cyanobacterial contaminated water in 1878, lots of aquatic organism, birds and domestic animals were affected by microcystin. The most shocking human accident occurred at Caruaru hemodialysis center in Brazil in 1996, when 52 renal dialyzed patients died from liver failure resulting from cyanobacterial contamination of the water used for renal dialysis.Microcysin (MC) is one of the most common and potent cyanobacterial toxins. Research has indicated that microcystin which was evaluated as being Group 2B has tumor-promoting activity. Epidemiological studies have suggested that microcystin is a risk factor for the high incidence of primary liver cancer and high mortality of male stomach cancer in certain area where people have consumed water contaminated blue-green algae. It is reported that microcystin, hepatitis B virus and aflatoxin have become three main risk factors for liver cancer in environment.The tumor-promoting mechanism of microcystin is still not clear. It is known that the change of genetic materials in cells could induce carcinogenesis, teratogenesis and mutagenesis. Most cancer occurs because of genetic material change. It is well known that tumor development has close relationship with the damage of genetic materials.Zhejiang Province is situated on China’s southeastern coast, on the southern part of the Yangzi River Delta. In this province, the total amount of water resources are relatively rich, but the average water resource per capita is below the mean level of the country because of the high population density. Based on the analysis data of organic pollutant in drinking water sources provided by Zhejiang Province Environment Monitoring Center, microcystin has become the main typical pollutant in drinking water sources, especially in Taihu Lake. It is the first health risk assessment of organic pollutants in drinking water sources in Zhejiang province. The genotoxicity study of microcystins in drinking water sources has profound theoretical and practical significance.Objective1. To evaluate the health risk caused by organic pollutants in drinking water sources via drinking water.2. To discuss the genotoxicity of MCLR and MCRR in drinking water source, measure DNA breakages by single cell gel electrophoresis (SCGE), investigate the mutagenicity by Ames test, and detect the chromosome damage by micronucleus test.Methods1. Health risk assessment of organic pollutants in drinking water sourceBased on the analysis data of organic pollutant in drinking water sources provided by Zhejiang province, a professional assessment model of water pollution was applied to evaluate the health risk caused by organic pollutants detected in drinking water sources.2. The genotoxicity of MC extracts and MC-containing water samplesSurface water of 2 typical drinking water source A and B were sampled, which were relatively seriously polluted by MC. The diluted microcystins of MCLR and MCRR were added to the water samples respectively, while MC-containing purified water was prepared. The HLB resin was used to absorb and concentrate the microcystin in source water samples. The bacteria, human peripheral blood lymphocytes and ornamental carp erythrocyte were treated by purified water, drinking water source A and B, concentrated water samples, and MC-containing purified water, respectively. The mutation of bacterial DNA was assessed by Ames test. The DNA damage of human peripheral blood lymphocytes was tested by comet assay. Micronucleus of ornamental carp erythrocyte was measured by micronucleus test.Results1. Glyphosate, MCLR, MCRR, DEHP, DBP and carbazole are the main organic pollutants, and Glyphosate, MCLR, MCRR are typical organic pollutants in drinking water source in this study. The health risks caused by organic pollutant is relatively slight, the drinking source water is relatively safe.2. MC extracts and MC-containing purified water could result in DNA damage of human peripheral blood lymphocytes. Compared with pure MC, the level of DNA damage caused by MC-containing purified water has significant differences.3. Ames test showed that DNA mutation induced by MC extracts, pure MC and MC-containing purified water were not observed.4. MC-containing water samples were able to induce higher frequency of micronucleus in carp erythrocyte, while the chromosome damage induced by MC extracts were not observed.Conclusions1. The organic pollution degree in drinking water sources was relatively slightly, the health risk caused by organic pollutants in drinking water source was much lower than the maximum allowance levels recommended by ICRP.2. MC extracts and MC-containing water samples were able to induce DNA damage of human peripheral blood lymphocytes, increase frequency of micronucleus in carp erythrocyte, but DNA mutation in Ames test were not observed.更多还原