鄭欣,劉婷婷,王一喆,王曉南,劉征濤,張亞輝,楊霓云,閆振廣
中國(guó)環(huán)境科學(xué)研究院,環(huán)境基準(zhǔn)與風(fēng)險(xiǎn)評(píng)估國(guó)家重點(diǎn)實(shí)驗(yàn)室,國(guó)家環(huán)境保護(hù)化學(xué)品生態(tài)效應(yīng)與風(fēng)險(xiǎn)評(píng)估重點(diǎn)實(shí)驗(yàn)室,北京 100012
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三氯生毒性效應(yīng)及水質(zhì)基準(zhǔn)研究進(jìn)展
鄭欣,劉婷婷,王一喆,王曉南,劉征濤,張亞輝,楊霓云,閆振廣*
中國(guó)環(huán)境科學(xué)研究院,環(huán)境基準(zhǔn)與風(fēng)險(xiǎn)評(píng)估國(guó)家重點(diǎn)實(shí)驗(yàn)室,國(guó)家環(huán)境保護(hù)化學(xué)品生態(tài)效應(yīng)與風(fēng)險(xiǎn)評(píng)估重點(diǎn)實(shí)驗(yàn)室,北京 100012
摘要:三氯生(TCS)是一種高效的廣譜抗菌劑,廣泛用于個(gè)人護(hù)理品和工業(yè)產(chǎn)品中,在水體和陸生環(huán)境及生物體內(nèi)均被檢測(cè)到,具有較高的潛在生態(tài)風(fēng)險(xiǎn)。文章綜述了近年來(lái)國(guó)內(nèi)外有關(guān)三氯生的生物毒性效應(yīng),分別對(duì)其在生物分子水平、細(xì)胞水平、組織器官水平及個(gè)體水平的毒性效應(yīng)進(jìn)行了分析總結(jié)。此外,對(duì)三氯生的水質(zhì)基準(zhǔn)研究現(xiàn)狀進(jìn)行了分析,并對(duì)其可能的研究方向進(jìn)行了探討。相關(guān)研究發(fā)現(xiàn),三氯生可對(duì)水生生物特別是藻類(lèi)產(chǎn)生較高的急性毒性。三氯生可在生物分子水平上產(chǎn)生毒性效應(yīng),影響酶和基因的正常表達(dá)及生理功能;還可產(chǎn)生細(xì)胞毒性,導(dǎo)致生物體組織器官產(chǎn)生畸變、癌變。三氯生對(duì)生物體具有顯著的內(nèi)分泌干擾效應(yīng),可擾亂生物體的生殖系統(tǒng)、甲狀腺系統(tǒng)和神經(jīng)系統(tǒng)的正常生理功能。但目前還沒(méi)有充分的證據(jù)表明,通過(guò)日常使用個(gè)人護(hù)理品攝入的三氯生會(huì)對(duì)人體產(chǎn)生毒性效應(yīng)。此外,雖然三氯生在水體中具有較高的暴露風(fēng)險(xiǎn),但其水質(zhì)標(biāo)準(zhǔn)基準(zhǔn)研究并不完善,相關(guān)研究還較少。鑒于三氯生對(duì)水生生物具有較高的毒性效應(yīng),今后應(yīng)加強(qiáng)三氯生水質(zhì)基準(zhǔn)方面的研究,不斷豐富三氯生的水生生物毒性數(shù)據(jù)庫(kù),并進(jìn)一步探索其在生物分子水平上的水質(zhì)基準(zhǔn)研究,以建立更科學(xué)有效的水質(zhì)基準(zhǔn)和標(biāo)準(zhǔn)。
關(guān)鍵詞:三氯生;急性毒性;分子細(xì)胞毒性;致畸致癌性;內(nèi)分泌干擾性;水質(zhì)基準(zhǔn)
引用格式:鄭欣, 劉婷婷, 王一喆, 王曉南, 劉征濤, 張亞輝, 楊霓云, 閆振廣. 三氯生毒性效應(yīng)及水質(zhì)基準(zhǔn)研究進(jìn)展[J]. 生態(tài)環(huán)境學(xué)報(bào), 2016, 25(3): 539-546.
ZHENG Xin, LIU Tingting, WANG Yizhe, WANG Xiaonan, LIU Zhengtao, ZHANG Yahui, YANG Niyun, YAN Zhenguang. Research Progress on the Toxic Effects and Water Quality Criteria of Triclosan [J]. Ecology and Environmental Sciences, 2016, 25(3): 539-546.
三氯生(Triclosan,TCS)作為一種廣譜抗菌劑,被廣泛應(yīng)用于個(gè)人護(hù)理產(chǎn)品(如牙膏、化妝品)、日用消費(fèi)類(lèi)產(chǎn)品(如纖維織品)、醫(yī)療用品(如牙科類(lèi)耗材、醫(yī)用殺菌劑等)以及家居清潔用品(Daughton et al.,1999)。TCS的大量應(yīng)用使其在各種環(huán)境介質(zhì)中廣泛存在,其主要通過(guò)污水廠(chǎng)出水排放進(jìn)入水體,最終進(jìn)入到地表水、土壤和地下水,現(xiàn)已在污水處理廠(chǎng)進(jìn)出水、污泥、河流、河口及沉積物中都有檢測(cè)到TCS(Chu et al.,2007;Chalew et al.,2009)。據(jù)調(diào)查,美國(guó)表層水體中TCS的質(zhì)量濃度為250~850 ng·L-1(Capdevielle et al.,2007),中國(guó)河流(遼河、海河、黃河、珠江和東江)表層水體中TCS質(zhì)量濃度高達(dá)478 ng·L-1,在沉積物中的質(zhì)量濃度高達(dá)2723 ng·L-1(Zhao et al.,2013)。TCS為疏水性物質(zhì),其辛醇水分配比(Kow)為4.8,具有在生物體內(nèi)富集的趨勢(shì)。研究調(diào)查顯示,TCS在水生植物(如剛毛藻Cladophora、寬葉香蒲Typha latifolia L.等)、水生動(dòng)物(如海豚),甚至人類(lèi)血漿和母乳中均有較高的檢出率(高海萍等,2012)。
隨著TCS在環(huán)境介質(zhì)和生物體內(nèi)檢出率的逐年升高,其對(duì)生態(tài)環(huán)境和人類(lèi)健康的潛在威脅越來(lái)越受到關(guān)注。研究發(fā)現(xiàn),TCS可使污水處理系統(tǒng)產(chǎn)生大量抗性細(xì)菌,這些抗性細(xì)菌隨出水排放到環(huán)境中,可能對(duì)生態(tài)環(huán)境造成較大的危害(Pruden,2014)。此外,TCS由于具有親脂性,可長(zhǎng)期在生物體內(nèi)累積,對(duì)生物具有潛在的威脅(周世兵等,2008)。目前,已有大量研究探索了TCS對(duì)生物可能產(chǎn)生的毒性效應(yīng),本文對(duì)這些研究成果進(jìn)行了系統(tǒng)性描述,發(fā)現(xiàn)TCS對(duì)生物體在個(gè)體水平乃至分子水平均可產(chǎn)生毒性效應(yīng)。
鑒于TCS對(duì)生物的急慢性毒性效應(yīng)和生理生態(tài)毒性,許多國(guó)家對(duì)食品和個(gè)人護(hù)理品中TCS的添加量進(jìn)行了限制(Dayan et al.,2007),但是卻很少有國(guó)家對(duì)TCS在水體中的濃度設(shè)定安全閾值。近些年TCS在我國(guó)水體中的暴露潛勢(shì)逐漸上升,顯示出較高的生態(tài)風(fēng)險(xiǎn)(Chen et al.,2014)。然而相關(guān)的基準(zhǔn)標(biāo)準(zhǔn)研究并不完善,對(duì)水質(zhì)管理造成了一定的困難。本文對(duì)TCS的水質(zhì)基準(zhǔn)研究現(xiàn)狀進(jìn)了分析,并探討了可能的研究方向,以期建立更加完善合理的水質(zhì)基準(zhǔn),為T(mén)CS的標(biāo)準(zhǔn)制定和生態(tài)風(fēng)險(xiǎn)預(yù)防管理提供參考。
TCS在水體中廣泛存在,其對(duì)水生生物的毒性效應(yīng)是殺菌效果的100~1000倍(Chalew et al.,2009)。本文從相關(guān)文獻(xiàn)及數(shù)據(jù)庫(kù)中搜集整理了TCS對(duì)水生生物的急性毒性數(shù)據(jù)(表1),毒性數(shù)據(jù)涉及到的生物包括水生植物、魚(yú)類(lèi)、兩棲類(lèi)、甲殼類(lèi)、軟體動(dòng)物、昆蟲(chóng)等。其中,對(duì)TCS最敏感的前5種生物均為藻類(lèi),與之前的研究結(jié)論一致(高海萍等,2012;Dann et al.,2011)。除藻類(lèi)外,魚(yú)類(lèi)也表現(xiàn)出很高的敏感性,如泥鰍Misgurnus anguillicaudatus和麥穗魚(yú)Pseudorasbora parva的敏感性?xún)H次于藻類(lèi)。
表1 三氯生的水生生物急性毒性Table 1 Acute toxicity of triclosan on aquatic organisms
表2顯示,TCS可對(duì)生物體產(chǎn)生分子水平的毒性效應(yīng)。TCS在酶和蛋白水平上的毒性效應(yīng)表現(xiàn)為,TCS可通過(guò)誘導(dǎo)氧化壓力對(duì)生物體內(nèi)的抗氧化酶系統(tǒng)產(chǎn)生抑制作用,如氧化物歧化酶(SOD)、丙二醛(MDA)、氨基比林N-脫甲基酶(APND)、過(guò)氧化氫酶(CAT)和谷胱甘肽-S-轉(zhuǎn)移酶(GST);并對(duì)生物體的細(xì)胞色素氧化酶系統(tǒng)產(chǎn)生影響,如P450、CYP1A等;此外,還有研究顯示TCS可影響熱休克蛋白Hsp70的表達(dá)(Liang et al.,2013;Peng et al.,2013;Binelli et al.,2009;Pedriali,2012;武小燕,2013;Lin et al.,2010;Lin et al.,2014)?;蛩降挠绊懕憩F(xiàn)為,TCS可直接導(dǎo)致DNA的損傷,也可能作為加合物對(duì)DNA的合成產(chǎn)生影響,干擾DNA的正常生理遺傳功能(Binelli et al.,2009;Pedriali,2012;Lin et al.,2014)。此外,TCS可通過(guò)干擾細(xì)胞內(nèi)分子信號(hào)的傳導(dǎo)對(duì)機(jī)體產(chǎn)生毒性效應(yīng)。利用熒光探針的流式細(xì)胞儀測(cè)定TCS對(duì)小鼠胸腺細(xì)胞中Zn2+濃度的影響,發(fā)現(xiàn)亞致死濃度的TCS可誘導(dǎo)細(xì)胞內(nèi)的氧化應(yīng)激反應(yīng),導(dǎo)致與硫醇蛋白結(jié)合的Zn2+釋放,促使細(xì)胞內(nèi)Zn2+濃度升高,導(dǎo)致機(jī)體免疫力下降(Tamura et al.,2012)。此外,還有研究顯示TCS可限制L型Ca2+在心肌細(xì)胞和骨骼肌細(xì)胞相關(guān)信號(hào)通路中的轉(zhuǎn)導(dǎo),導(dǎo)致心肌和骨骼肌收縮力的減弱,相關(guān)證據(jù)包括:暴露在TCS中不到20 min,麻醉小鼠的心臟功能減弱了25%;向小鼠施以單劑量的TCS,60 min后小鼠的握力減弱了18%;黑頭鰷魚(yú)Fathead minnow在TCS中暴露7 d后,游泳速度比正常魚(yú)類(lèi)顯著降低(Ahn et al.,2008;Cherednichenkoa et al.,2012)。
表2 TCS對(duì)生物體的酶和基因毒性Table 2 Toxic effects of TCS on enzyme and gene
表3 TCS的細(xì)胞毒性效應(yīng)Table 3 Mutagenic and carcinogenic effects of TCS
TCS是否具有致突變和致癌效應(yīng)一直存有爭(zhēng)議(表3)。有研究者以沙門(mén)菌株為對(duì)象進(jìn)行致突變?cè)囼?yàn),結(jié)果并未發(fā)現(xiàn)突變效應(yīng)(Onodera et al., 1995)。但由于TCS對(duì)于細(xì)菌本身就是高毒性物質(zhì),其致突變效應(yīng)難于檢測(cè),因此以細(xì)菌類(lèi)生物作為致突變效應(yīng)的試驗(yàn)對(duì)象并不合理,其研究結(jié)果還有待進(jìn)一步確認(rèn)(Rodricks et al.,2010)。而其后的研究中,部分研究顯示TCS可促進(jìn)癌細(xì)胞的增殖,如人類(lèi)肝癌細(xì)胞、卵巢癌細(xì)胞、前列腺癌細(xì)胞和乳腺癌細(xì)胞(Ma et al.,2013;Yueh et al.,2014;Kim et al.,2014;Kim et al.,2015;Henry et al.,2013)。還有一部分研究卻顯示TCS對(duì)癌細(xì)胞有抑制作用,如前列腺癌細(xì)胞、乳腺癌細(xì)胞、人類(lèi)眼癌細(xì)胞、上皮癌細(xì)胞和絨毛膜癌細(xì)胞(Sadowski et al.,2014;Liu et al.,2002;Deepa et al.,2012;Honkisz et al.,2012;Schmid et al.,2005)。值得注意的是,以前列腺癌細(xì)胞和乳腺癌細(xì)胞為試驗(yàn)對(duì)象的研究均出現(xiàn)了相反的作用效果,差異的原因還有待于進(jìn)一步研究。機(jī)理研究顯示,TCS對(duì)癌細(xì)胞增殖的效應(yīng)可能是通過(guò)雌/雄激素介導(dǎo)的信號(hào)通路調(diào)控與細(xì)胞周期和凋亡有關(guān)的周期蛋白D1、P21和Bax的表達(dá),從而促進(jìn)癌細(xì)胞的生長(zhǎng)(Yueh et al.,2014;Kim et al.,2014);而抑制作用則是通過(guò)對(duì)FAS表達(dá)的限制引起的,TCS對(duì)癌細(xì)胞產(chǎn)生促進(jìn)效應(yīng)還是抑制效應(yīng)可能與某些條件有關(guān),但仍需進(jìn)一步探索(Henry et al.,2013)。此外,上述研究均是以癌細(xì)胞為試驗(yàn)對(duì)象,并不能證明TCS會(huì)誘導(dǎo)正常細(xì)胞的畸變或癌化。研究顯示,TCS在相似范圍內(nèi)對(duì)良性細(xì)胞并未顯示出細(xì)胞毒性,如米勒神經(jīng)膠質(zhì)細(xì)胞和纖維母細(xì)胞(Honkisz et al.,2012;Schmid et al.,2005)。推測(cè)其原因?yàn)?,F(xiàn)AS在癌細(xì)胞中有較高的含量,在正常細(xì)胞中則含量較少(Brusselmans et al.,2009),由于TCS可通過(guò)抑制FAS對(duì)細(xì)胞產(chǎn)生毒性作用,因此TCS對(duì)癌細(xì)胞的影響要大于正常細(xì)胞,但該推測(cè)有待研究進(jìn)行驗(yàn)證。
4.1 生殖系統(tǒng)毒性
TCS與雌激素在結(jié)構(gòu)上相似,可通過(guò)與內(nèi)源性雌激素競(jìng)爭(zhēng)結(jié)合雌激素受體(ER),從而直接影響ER的促轉(zhuǎn)錄活性,引起雌激素效應(yīng)(或抗雄激素效應(yīng))。如表4顯示,TCS可加快雌鼠的性成熟,增加其子宮重量;并可使孕鼠產(chǎn)道開(kāi)口提前;對(duì)于雄鼠,TCS可降低其睪丸、前列腺等性腺器官的重量,顯著減少雄激素相關(guān)蛋白及固醇生成酶的基因表達(dá),并降低血清中雄性相關(guān)激素的水平,TCS可在雄鼠副睪中累積,引起其組織形態(tài)發(fā)生改變,并對(duì)精子的形態(tài)和數(shù)量產(chǎn)生影響。表4還顯示,TCS可提高雄性水生動(dòng)物體卵黃原蛋白的含量,并對(duì)其精子的形態(tài)和數(shù)量產(chǎn)生影響。體外細(xì)胞試驗(yàn)也顯示,TCS可限制睪丸間質(zhì)細(xì)胞中黃體生成素和絨膜促性腺激素誘導(dǎo)的睪酮的生成,其可能的機(jī)制是:環(huán)腺苷酸(cAMP)具有調(diào)節(jié)神經(jīng)遞質(zhì)合成,促進(jìn)激素分泌的作用,而TCS可降低腺苷酸環(huán)化酶的活性,減少cAMP的產(chǎn)量并抑制固醇生成酶基因的轉(zhuǎn)錄和表達(dá),導(dǎo)致固醇系統(tǒng)的紊亂,從而抑制睪丸素的合成。雖然TCS在結(jié)構(gòu)上與雌激素相似,但卻可以顯示出一定的雄激素效應(yīng)(或抗雌激素效應(yīng))。如表4所示,TCS可抑制羊胎盤(pán)中雌激素硫酸轉(zhuǎn)移酶的活性,影響胎盤(pán)對(duì)胎兒的雌激素供給;可改變雄性青鳉魚(yú)的鰭長(zhǎng)并可能對(duì)其性別比例產(chǎn)生影響,還可降低非洲爪蟾血清中卵黃原蛋白和睪酮的水平;體外乳腺癌細(xì)胞試驗(yàn)也顯示,TCS可增強(qiáng)二氫睪酮調(diào)節(jié)的雄激素受體應(yīng)答基因的轉(zhuǎn)錄激活,其增強(qiáng)作用可達(dá)到180%。
機(jī)理研究顯示,TCS可分別與細(xì)胞中的雌激素受體和雄激素受體結(jié)合,既顯示出雌激素效應(yīng)又顯示出雄激素效應(yīng);同時(shí),在與雌激素或雄激素共存時(shí),卻可分別限制雌激素誘導(dǎo)的ERE-CAT受體的表達(dá)和雄激素誘導(dǎo)的LTR-CAT受體的表達(dá),顯示出抗雌激素活性或抗雄激素活性(Henry et al.,2013)。TCS顯示出抗雌激素活性的性質(zhì)與其他外源性雌激素(如對(duì)羥苯甲酸酯、多氯聯(lián)苯、己烯雌酚等)相比比較特別,因?yàn)楹笳咧伙@示出雌激素活性而未顯示抗雌激素活性,這種差異可能是由于它們?cè)诜肿咏Y(jié)構(gòu)上存在差異以及它們與受體結(jié)合模式上存在差異,其機(jī)理需要更深入的研究(Byford et al.,2002;Darbre et al.,2002)。
4.2 甲狀腺系統(tǒng)毒性
表4 TCS對(duì)生殖系統(tǒng)的毒性效應(yīng)Table 4 Toxic effects of TCS on reproductive system
TCS的內(nèi)分泌干擾性還表現(xiàn)為對(duì)生物體甲狀腺系統(tǒng)的影響(表5)(Schuur et al.,1998;Veldhoen et al.,2006;Crofton et al.,2007;Paul et al.,2010;Paul et al.,2012;Paul et al.,2013;Pinto et al.,2013)。TCS可通過(guò)間接的方式對(duì)甲狀腺系統(tǒng)代謝產(chǎn)生影響,如TCS可降低生物體內(nèi)甲狀腺激素受體α的轉(zhuǎn)錄水平,或抑制T2磺基轉(zhuǎn)移酶的活性,對(duì)甲狀腺激素介導(dǎo)的生長(zhǎng)發(fā)育過(guò)程產(chǎn)生影響。此外,還有學(xué)者推測(cè)TCS可通過(guò)PXR和CAR信號(hào)通路上調(diào)肝酶代謝相關(guān)基因的表達(dá),增強(qiáng)對(duì)甲狀腺素T4的代謝,從而導(dǎo)致生物體內(nèi)甲狀腺素水平的降低,引起低甲狀腺素血癥。然而,其后的一些研究并未能提供有力支持,該假設(shè)有待于進(jìn)一步驗(yàn)證(Zorrilla et al.,2009;Paul et al.,2012;Paul et al.,2013)。除了通過(guò)間接方式對(duì)甲狀腺系統(tǒng)代謝產(chǎn)生影響,TCS也可能直接對(duì)甲狀腺組織及其激素產(chǎn)生影響。研究顯示,TCS可引起斑馬魚(yú)體內(nèi)促甲狀腺激素(TSH)和碘化鈉載體(NIS)相關(guān)基因的上調(diào)表達(dá),并可引起甲狀腺組織形態(tài)學(xué)上的畸變,但其機(jī)制還有待于進(jìn)一步研究(Pinto et al.,2013)。
TCS作為內(nèi)分泌干擾物質(zhì),相關(guān)研究多集中于其對(duì)生殖系統(tǒng)和甲狀腺系統(tǒng)影響,關(guān)于其對(duì)神經(jīng)系統(tǒng)影響的研究則比較少。Szychowski et al.(2015)首次對(duì)TCS的神經(jīng)毒性機(jī)制進(jìn)行了研究,發(fā)現(xiàn)TCS可通過(guò)誘導(dǎo)FasR和caspase-8的表達(dá)來(lái)激活外部細(xì)胞凋亡信號(hào)通路,從而引起腦內(nèi)神經(jīng)元細(xì)胞的凋亡。但TCS是否還可以通過(guò)其他途徑對(duì)神經(jīng)系統(tǒng)產(chǎn)生影響還需要更多的探索。研究顯示,與TCS在結(jié)構(gòu)上非常相似的三氯卡班(TCC)能夠通過(guò)增強(qiáng)外源性雌激素誘導(dǎo)的芳香化酶AroB的過(guò)度表達(dá),對(duì)腦組織的發(fā)育產(chǎn)生影響(Chung,2011),因此是否可以推測(cè)TCS也能通過(guò)與TCC相似的機(jī)制對(duì)腦組織產(chǎn)生影響還需要研究進(jìn)行驗(yàn)證。此外,由于甲狀腺對(duì)腦組織的發(fā)育有重要作用,而TCS可對(duì)生物體的甲狀腺系統(tǒng)產(chǎn)生影響(Pinto et al.,2013),因此推測(cè)TCS也可能通過(guò)影響甲狀腺系統(tǒng)從而對(duì)腦神經(jīng)系統(tǒng)的發(fā)育產(chǎn)生危害,但此機(jī)制還需要進(jìn)一步驗(yàn)證。
關(guān)于TCS對(duì)人體的毒性作用,大多進(jìn)行的是體外細(xì)胞試驗(yàn)研究。如利用人體乳腺癌細(xì)胞進(jìn)行的TCS毒性檢測(cè),顯示TCS可以促進(jìn)人體乳腺癌細(xì)胞的增殖;以及利用人體間充質(zhì)干細(xì)胞進(jìn)行的體外細(xì)胞試驗(yàn),顯示TCS在低濃度(0.156~2.5 μmol·L-1下會(huì)抑制人體hMSCs脂肪細(xì)胞的分化(Guo et al.,2012)。盡管TCS在人體外細(xì)胞試驗(yàn)中顯示出一定的毒性效應(yīng),但還沒(méi)有證據(jù)表明TCS可對(duì)人體產(chǎn)生毒性。Allmyr et al.(2009)研究了TCS對(duì)人體甲狀腺系統(tǒng)的影響,通過(guò)14 d的暴露檢測(cè),人體血液中TCS的含量顯著提高,但并未對(duì)甲狀腺激素及相關(guān)酶的活性產(chǎn)生影響,表明正常使用含TCS的個(gè)人護(hù)理品不會(huì)對(duì)人體的甲狀腺內(nèi)穩(wěn)態(tài)產(chǎn)生影響。Ros-Llor et al.(2014)研究認(rèn)為,即使頻繁使用含有TCS的口腔清洗劑也不會(huì)對(duì)人體產(chǎn)生基因毒性。Witorsch(2014)通過(guò)對(duì)現(xiàn)有的關(guān)于TCS對(duì)哺乳動(dòng)物和人類(lèi)影響的相關(guān)文獻(xiàn)的整理,認(rèn)為現(xiàn)有研究雖然證明TCS可對(duì)動(dòng)物產(chǎn)生毒性,但其作用機(jī)制在人體內(nèi)是不存在的,因此通過(guò)日常使用個(gè)人護(hù)理品而攝入的TCS,不具有對(duì)人體產(chǎn)生內(nèi)分泌干擾的風(fēng)險(xiǎn)。TCS對(duì)人體不產(chǎn)生毒性效應(yīng)的原因可能是,TCS在人體內(nèi)并不持久,會(huì)在24 h內(nèi)被快速排出體外,因此在人體內(nèi)的積累較少(Sandborgh-Englund et al.,2006)。即使有報(bào)道顯示,人體乳液中的TCS含量可高達(dá)2.1 mg·kg-1,但仍會(huì)通過(guò)人體可能的解毒機(jī)制逐漸消除,但這種解毒機(jī)制還有待于進(jìn)一步研究(Dayan,2007)。
表5 TCS對(duì)甲狀腺系統(tǒng)的毒性效應(yīng)Table 5 Toxic effects of TCS on thyroid system
雖然研究顯示TCS具有潛在的生態(tài)風(fēng)險(xiǎn),但由于TCS屬于一種新型污染物,關(guān)于其標(biāo)準(zhǔn)的制定還比較欠缺,如我國(guó)地表水水質(zhì)標(biāo)準(zhǔn)還未有關(guān)于其標(biāo)準(zhǔn)閾值的規(guī)定。此外,TCS的水質(zhì)基準(zhǔn)的研究也比較少,美國(guó)等發(fā)達(dá)國(guó)家還沒(méi)有關(guān)于其水質(zhì)基準(zhǔn)的研究。最近,我國(guó)學(xué)者利用10種中國(guó)本土水生生物進(jìn)行了TCS的急慢性試驗(yàn),并推導(dǎo)出TCS的急性基準(zhǔn)值(Criteria Maximum Concentration,CMC)和慢性基準(zhǔn)值(Criteria Continuous Concentration,CCC)分別為0.009和0.002 mg·L-1(Wang et al.,2013),該結(jié)果對(duì)于我國(guó)制定TCS的水質(zhì)標(biāo)準(zhǔn)制訂具有一定的指導(dǎo)意義。
通常水質(zhì)基準(zhǔn)是建立在個(gè)體水平毒性數(shù)據(jù)的基礎(chǔ)上,如急性水質(zhì)基準(zhǔn)的建立是以L(fǎng)C50或EC50為毒性終點(diǎn),慢性水質(zhì)基準(zhǔn)的建立是以最低有影響濃度LOEC或最大無(wú)影響濃度NOEC等為毒性終點(diǎn)。然而,當(dāng)生物體暴露于污染物時(shí),基因表達(dá)的改變通常要先于細(xì)胞、組織、個(gè)體和群體的改變,相比于個(gè)體水平的生存指標(biāo)或生殖指標(biāo),基因表達(dá)水平上的響應(yīng)更具有早期預(yù)警的作用,因此基因毒性數(shù)據(jù)可能比急慢性毒性數(shù)據(jù)更為敏感(Menzel et al.,2009)。但其后的研究并不能為該假設(shè)提供有力證明,部分重金屬(Cd、Zn)的研究顯示出相反的趨勢(shì),即其基因毒性數(shù)據(jù)敏感性遠(yuǎn)低于其慢性毒性數(shù)據(jù)(Fedorenkova et al.,2010;Yan et al.,2012)。這可能是由多方面的原因造成的,如相關(guān)的毒性數(shù)據(jù)較少,使研究結(jié)果的可靠性降低;此外,試驗(yàn)數(shù)據(jù)的目標(biāo)基因可能并不是對(duì)污染物最敏感的響應(yīng)基因,造成了基因毒性數(shù)據(jù)的敏感性低于個(gè)體水平的慢性數(shù)據(jù)。因此,基因毒性數(shù)據(jù)是否能應(yīng)用于水質(zhì)基準(zhǔn)的研究仍需要進(jìn)一步的驗(yàn)證,而TCS由于基因毒性數(shù)據(jù)較少,還未有相關(guān)方面的研究。
此外,污染物質(zhì)對(duì)生物的毒性作用常常存在著Hormesis效應(yīng)(即低劑量促進(jìn),高劑量抑制效應(yīng)),且Hormesis的效應(yīng)濃度通常比NOEC低10倍左右(Stebbing et al.,1998)。也就是說(shuō),Hormesis效應(yīng)濃度可能是更嚴(yán)格意義上的無(wú)作用濃度,這有助于更準(zhǔn)確地劃定安全濃度,對(duì)生態(tài)風(fēng)險(xiǎn)評(píng)估有著重要意義(Chapman,2002)。在水質(zhì)基準(zhǔn)研究方面,將Hormesis效應(yīng)濃度作為毒性作用終點(diǎn),同時(shí)結(jié)合分子水平的毒性效應(yīng)來(lái)進(jìn)行水質(zhì)基準(zhǔn)的研究,可能會(huì)得出比現(xiàn)有的慢性基準(zhǔn)更為嚴(yán)格的水質(zhì)基準(zhǔn)值,但還未有相關(guān)方面的研究,其科學(xué)性和有效性有待于驗(yàn)證。
綜上,TCS可在分子和細(xì)胞水平上對(duì)生物造成影響,產(chǎn)生酶和基因毒性,導(dǎo)致生物體組織器官的突變和癌變。此外,TCS對(duì)生物體具有顯著的內(nèi)分泌干擾性,可通過(guò)對(duì)生殖發(fā)育系統(tǒng)、甲狀腺系統(tǒng)和神經(jīng)系統(tǒng)產(chǎn)生影響,造成生物內(nèi)穩(wěn)態(tài)的破壞,但相關(guān)的分子機(jī)制還需要加強(qiáng)研究。雖然TCS可對(duì)哺乳動(dòng)物產(chǎn)生毒性效應(yīng),但現(xiàn)有研究還不能證明TCS可對(duì)人體產(chǎn)生類(lèi)似的毒性效應(yīng),日常攝入的TCS不會(huì)對(duì)人體產(chǎn)生內(nèi)分泌干擾,但其清除機(jī)理有待于進(jìn)一步研究。此外,鑒于我國(guó)水體中TCS的暴露風(fēng)險(xiǎn)不斷上升,應(yīng)盡快擴(kuò)充TCS的本土毒性數(shù)據(jù),為進(jìn)一步完善其水質(zhì)基準(zhǔn)提供數(shù)據(jù)支持。另外,開(kāi)展以TCS為目標(biāo)污染物的基因組學(xué)研究,利用高通量技術(shù)篩選對(duì)TCS最敏感的響應(yīng)基因,有利于進(jìn)一步探索基因毒性數(shù)據(jù)應(yīng)用于水質(zhì)基準(zhǔn)研究的可能性。同時(shí),開(kāi)展TCS在基因水平的Hormesis效應(yīng)研究,以期從不同的視角探索水質(zhì)基準(zhǔn)研究的可能性,有利于更科學(xué)合理地制定水質(zhì)基準(zhǔn)標(biāo)準(zhǔn)。
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Research Progress on the Toxic Effects and Water Quality Criteria of Triclosan
ZHENG Xin, LIU Tingting, WANG Yizhe, WANG Xiaonan, LIU Zhengtao, ZHANG Yahui,YANG Niyun, YAN Zhenguang*
State Key Laboratory for Environmental Criteria and Risk Assessment, State Environment Protection Key Laboratory of Ecological Effects and Risk Assessment of Chinese, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Abstract:Triclosan (TCS), an effective broad antibacterial agent, has long been used in personal care products and industrial products. With inceasing high detection rates in aquatic environment, terrestrial environment and organisms, TCS poses potential ecological risks. This paper summarizes recent advances about the toxic effect of TCS to organisms at levels of molecular, cell, tissue and organ, and indivdual, respectivelly. It aslo analyzes the reseach status of water quality criteria related to triclosan, and discusses some possible research directions on this field. Researches show that TCS is acutely toxic to aquatic organisms, especially algae. At microscopic level, TCS presents molecular and cellular toxicity, disrupting the expression and physiological function of enzyme and gene, leading to the mutation and canceration in tissues and organs of organisms. Additionally, TCS could cause adverse effects on the reproductive system, thyroid system and nervous system of organisms, showing evident endocrine disruption. However currently,there is no strong evidence that TCS intake through personal care products could pose a threat to human health. Given the high exposure risk in aquatic environment, researches on water quality standards and criteria are relatively less. Future research on this field should be strengthened. We should make more researches on the toxic effect of TCS on aquatic organisms to enrich the toxicity database and a further exploration on the water quality criteria at molecular level.
Key words:triclosan; acute toxicity; molecular and cellular toxicity; mutagenic and carcinogenic; endocrine disruption; water quality criteria
DOI:10.16258/j.cnki.1674-5906.2016.03.025
中圖分類(lèi)號(hào):X171.5; X824
文獻(xiàn)標(biāo)志碼:A
文章編號(hào):1674-5906(2016)03-0539-08
基金項(xiàng)目:國(guó)家水體污染控制與治理科技重大專(zhuān)項(xiàng)(2012ZX07501-003-06);科技部科技基礎(chǔ)性工作專(zhuān)項(xiàng)(2014FY120600)
作者簡(jiǎn)介:鄭欣(1981年生),女,助理研究員,博士,從事水質(zhì)基準(zhǔn)研究。E-mail: Zhengxin@craes.org.cn
*通信作者
收稿日期:2015-08-18