馮新斌, 仇廣樂(lè), 王少鋒,2, 李?平, 孟?博

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我國(guó)汞礦區(qū)人群的無(wú)機(jī)汞及甲基汞暴露途徑與風(fēng)險(xiǎn)評(píng)估

馮新斌1*, 仇廣樂(lè)1, 王少鋒1,2, 李?平1, 孟?博1

(1. 中國(guó)科學(xué)院 地球化學(xué)研究所 環(huán)境地球化學(xué)國(guó)家重點(diǎn)實(shí)驗(yàn)室, 貴州 貴陽(yáng)?550002; 2. 中國(guó)科學(xué)院 沈陽(yáng)應(yīng)用生態(tài)研究所 污染生態(tài)與環(huán)境工程重點(diǎn)實(shí)驗(yàn)室, 遼寧 沈陽(yáng)?110016)

汞礦山活動(dòng)導(dǎo)致的環(huán)境汞污染及健康風(fēng)險(xiǎn), 一直受到人們的關(guān)注和重視。汞礦區(qū)生活人群的汞暴露主要是通過(guò)食物鏈、直接呼吸空氣以及飲水等途徑。人群汞暴露評(píng)估結(jié)果表明, 通過(guò)進(jìn)食稻米和蔬菜造成的無(wú)機(jī)汞暴露最高, 占總暴露量的80%以上, 它們的平均日暴露量分別為0.10 μg/kg和0.13 μg/kg; 而與無(wú)機(jī)汞暴露不同, 通過(guò)進(jìn)食稻米產(chǎn)生的甲基汞暴露量遠(yuǎn)遠(yuǎn)高出其他進(jìn)食途徑, 如蔬菜、魚(yú)類(lèi)和飲水等, 表現(xiàn)出了很高的風(fēng)險(xiǎn)因子, 最大日暴露量可高達(dá)1.9 μg/kg, 造成的風(fēng)險(xiǎn)因子高達(dá)8.1。盡管各途徑的平均日暴露量估算顯示無(wú)論無(wú)機(jī)汞還是甲基汞, 均未超出糧農(nóng)組織/世界衛(wèi)生組織食品添加劑聯(lián)合專(zhuān)家委員會(huì)(JECFA)推薦的人體安全無(wú)機(jī)汞攝入量0.57 μg/(kg·d)和安全甲基汞攝入量0.23 μg/(kg·d), 但它們的聯(lián)合暴露量導(dǎo)致的風(fēng)險(xiǎn)因子卻超出了1.0, 暗示可能會(huì)導(dǎo)致部分人群尤其是敏感人群, 如孕婦、嬰兒等的潛在汞暴露健康風(fēng)險(xiǎn)。

汞; 環(huán)境污染; 暴露途徑; 風(fēng)險(xiǎn)評(píng)估; 汞礦區(qū)

0 引 言

汞(Hg), 俗稱(chēng)水銀, 具有很強(qiáng)的毒性, 為人體非必需元素。汞可以單質(zhì)態(tài)長(zhǎng)時(shí)間(0.5~2 a)存在于大氣中并隨大氣循環(huán), 并能在環(huán)境中轉(zhuǎn)化為生物累積性更強(qiáng)的甲基汞(MeHg), 已被定義為一種全球性環(huán)境污染物[1]和持久性生物積累污染物(PBTs)[2]。隨著全球氣候變暖、酸雨、臭氧層耗損、森林砍伐以及礦山活動(dòng)等引發(fā)的環(huán)境變化, 全球汞的環(huán)境過(guò)程亦在不斷變化, 汞的環(huán)境污染問(wèn)題越來(lái)越引起人們的關(guān)注。隨著人們對(duì)全球環(huán)境的關(guān)注和對(duì)汞的毒性及危害的深入認(rèn)識(shí), 世界各國(guó)汞礦資源的大規(guī)模開(kāi)發(fā)活動(dòng)陸續(xù)停止, 但是不同國(guó)家和地區(qū)幾千年的汞礦冶煉史, 已經(jīng)造成了礦區(qū)土壤、水體以及大氣的嚴(yán)重汞污染。不同于其他重金屬, 汞在進(jìn)入環(huán)境后, 特定條件下毒性較弱的無(wú)機(jī)汞, 會(huì)轉(zhuǎn)化為毒性更大、生物有效性更強(qiáng)的甲基汞, 通過(guò)各種途徑進(jìn)入食物鏈, 構(gòu)成對(duì)人類(lèi)的危害[3–4]。

我國(guó)位于環(huán)太平洋汞礦化帶中, 分布著大量汞礦床, 例如, 云南洗馬塘汞礦、水銀廠汞礦; 貴州務(wù)川木油廠汞礦、萬(wàn)山汞礦、銅仁路臘汞礦、松桃汞礦、開(kāi)陽(yáng)白馬洞汞礦、興仁濫木廠汞礦、丹寨水銀廠汞礦、三都交梨汞礦; 湖南鳳凰茶田汞礦; 廣西益蘭汞礦; 重慶秀山汞礦; 陜西旬陽(yáng)青銅溝汞礦等。盡管我國(guó)大部分汞礦山已經(jīng)閉坑, 但生活在汞礦區(qū)的居民仍然會(huì)通過(guò)飲食、呼吸、皮膚接觸等, 長(zhǎng)期遭受高汞暴露。因此, 汞礦區(qū)環(huán)境中的汞污染, 不僅會(huì)對(duì)當(dāng)代居民造成人體傷害, 還會(huì)通過(guò)汞的生物積累和放大效應(yīng)對(duì)后代產(chǎn)生危害。了解汞礦區(qū)居民汞暴露途徑、估算居民生產(chǎn)生活過(guò)程中通過(guò)不同途徑而產(chǎn)生的汞暴露量、進(jìn)行居民健康風(fēng)險(xiǎn)評(píng)價(jià), 具有重要的現(xiàn)實(shí)意義。

1?汞礦山環(huán)境中汞的分布

大規(guī)模汞礦山活動(dòng)會(huì)產(chǎn)生大量的“三廢”(廢渣、廢水、廢氣), 會(huì)釋放大量的汞到周?chē)h(huán)境中, 礦山活動(dòng)區(qū)的近地表大氣、地表水體、表層土壤以及生長(zhǎng)的植物等均顯示出高汞濃度特征。

1.1 大氣汞

汞礦區(qū)的冶煉場(chǎng)所、爐渣、汞污染土壤和水體等都會(huì)向大氣排放氣態(tài)汞(TGM)。通常, 汞礦區(qū)大氣汞含量變化范圍非常大, 介于7.4~1950 ng/m3之間(表1), 受汞礦山活動(dòng)影響的區(qū)域近地表大氣汞含量明顯升高。造成區(qū)域大氣汞濃度急劇增加的主要原因, 多是由于正在進(jìn)行的汞冶煉活動(dòng), 尤其土法冶煉活動(dòng), 土法煉汞工藝回收裝置密封性差, 汞的回收率多低于70%[5]。汞污染土壤的去氣作用, 是大氣汞的另一個(gè)重要來(lái)源[6–8]。調(diào)查表明, 汞礦區(qū)表層土壤向大氣的汞釋放通量高達(dá)10500 ng/(m2·h), 導(dǎo)致近地表大氣汞含量高達(dá)8.4~440 ng/m3[8]。表層土壤汞的釋放來(lái)源于土壤中活性Hg2+的光致還原作用和Hg0的再釋放, 隨著光照強(qiáng)度增強(qiáng), 土壤中汞的釋放作用加強(qiáng), 近地表大氣汞濃度升高, 汞礦區(qū)土壤向大氣的汞釋放通量與土壤汞含量和光照強(qiáng)度具有明顯正相關(guān)性[8–10]。另外, 爐渣是含汞礦石高溫煅燒的產(chǎn)物, 它在冷卻過(guò)程中會(huì)吸附Hg0而使其成為礦區(qū)大氣汞的一個(gè)重要來(lái)源。估算顯示, 汞礦區(qū)約10%以上的大氣汞來(lái)自爐渣汞的釋放[11], 爐渣附近地表大氣汞的平均濃度高達(dá)(2110±1480) ng/m3[9]。

表1?我國(guó)汞礦區(qū)不同環(huán)境介質(zhì)汞含量分布

注: 本表數(shù)據(jù)引自課題組2002年至2012年監(jiān)測(cè)數(shù)據(jù)。無(wú)機(jī)汞(HgI)=總汞(HgT)-甲基汞(MeHg)。

1.2 水體汞

汞礦區(qū)受爐渣等影響的廢水中含有大量的汞, 汞礦區(qū)受爐渣影響的地表河流無(wú)機(jī)汞含量超過(guò)μg/L級(jí)[12], 多介于6.1~9260 ng/L之間, 我國(guó)汞礦區(qū)地表水體無(wú)機(jī)汞平均含量達(dá)730 ng/L (表1), 由于水體汞形態(tài)多以顆粒態(tài)為特征, 因此水體汞濃度變化明顯受季節(jié)降雨量控制, 豐水期水體汞含量顯著高于枯水期。汞污染水體是礦區(qū)汞污染物遷移擴(kuò)散的重要載體, 有大量汞隨地表徑流向下游遷移, 使汞污染范圍擴(kuò)大。調(diào)查表明, 斯洛文尼亞Idrija汞礦自1994年閉坑至1997年的3年間便有1.5 t金屬汞隨著礦山廢水遷移至下游100 km的愛(ài)琴海[13], 該部分汞在新的環(huán)境中, 成為了“二次”汞污染源。汞污染水體還表現(xiàn)出很強(qiáng)的甲基化趨勢(shì), 甲基汞含量介于0.022~25 ng/L之間(表1)。調(diào)查表明, 當(dāng)?shù)V區(qū)汞污染水體中硫酸鹽濃度升高時(shí), 硫酸鹽還原菌活動(dòng)大大增強(qiáng), 可顯著提高水體汞的甲基化能力[14–15]。汞礦區(qū)水體的甲基化, 會(huì)成為下游濕地、湖泊和水庫(kù)生態(tài)系統(tǒng)中新的汞污染源和甲基汞的來(lái)源。

1.3 土壤汞

通常汞礦區(qū)土壤受礦山活動(dòng)影響, 其汞污染具有含量高、變化范圍廣及表層污染重等特點(diǎn)。礦區(qū)土壤汞含量0.10~790 mg/kg, 平均達(dá)到93 mg/kg (表1), 顯著高出對(duì)照區(qū)土壤汞含量0.10~1.2 mg/kg。土壤剖面分析發(fā)現(xiàn), 汞污染土壤主要集中在表層0~30 cm內(nèi), 到45 cm以下土壤汞含量趨于背景值。嚴(yán)重汞污染的土壤通常受到了爐渣影響, 汞的主要存在形態(tài)是HgS, 占總含量的60%~80%, 其含量與土壤中的粗顆粒組分含量具明顯正相關(guān)關(guān)系, 當(dāng)HgS含量降低時(shí), 揮發(fā)性的單質(zhì)汞含量比率升高, 且與水溶態(tài)汞、酸溶態(tài)汞、有機(jī)結(jié)合態(tài)汞的含量呈明顯正相關(guān)性[16]。汞污染土壤同樣表現(xiàn)出強(qiáng)的汞甲基化, 土壤甲基汞含量介于0.091~20 μg/kg之間, 顯著高于對(duì)照區(qū)土壤甲基汞含量0.10~0.28 μg/kg, 且稻田土壤甲基汞含量明顯高于旱土土壤[17–19]。溫度、有機(jī)質(zhì)、土壤pH、微生物以及土壤的氧化還原條件等, 均可以對(duì)汞的甲基化產(chǎn)生影響, 不同季節(jié)的變化會(huì)顯著影響汞的凈甲基化速率, 夏季汞的去甲基化速率小于1.9%/d, 明顯低于春季汞的去甲基汞化速率4.1%/d[20]。盡管甲基汞占總汞比率小于0.1%, 但其強(qiáng)的毒性及生物有累積性, 無(wú)疑會(huì)對(duì)農(nóng)作物產(chǎn)生重要的影響。

1.4 生物汞

汞礦區(qū)稻米、蔬菜中的高含量汞的測(cè)定結(jié)果表明, 汞可被農(nóng)作物強(qiáng)烈吸收并在體內(nèi)積累。調(diào)查數(shù)據(jù)顯示, 礦區(qū)污染場(chǎng)地種植的卷心菜、玉米、稻米等中的汞含量(表1), 遠(yuǎn)遠(yuǎn)超出我國(guó)食品衛(wèi)生飲食標(biāo)準(zhǔn)規(guī)定的0.01~0.02 mg/kg。更令人關(guān)注的是, 稻米中積累了很高的甲基汞, 可高達(dá)180 μg/kg, 成為礦區(qū)人群暴露甲基汞的重要途徑[21–26]。調(diào)查發(fā)現(xiàn), 水稻體內(nèi)甲基汞來(lái)源于土壤, 稻米對(duì)甲基汞的積累表現(xiàn)為“吸收-運(yùn)移-富集”的動(dòng)態(tài)過(guò)程[27–29]。稻田作為一種特殊的濕地生態(tài)系統(tǒng), 為硫酸鹽還原菌(甲基化細(xì)菌)提供了理想的生存條件, 因而成了汞甲基化的理想場(chǎng)所[30–32], 來(lái)自礦區(qū)的汞污染河流的灌溉水和高濃度大氣汞沉降為稻田提供了充足的汞源, 這些新輸入的尤其高大氣汞背景下產(chǎn)生的大氣新沉降汞(新汞), 它們?cè)谖⑸镒饔孟? 更易于被轉(zhuǎn)化為高神經(jīng)毒性的甲基汞[27–28]。進(jìn)一步的調(diào)查發(fā)現(xiàn), 季節(jié)性水淹促進(jìn)了汞甲基化作用過(guò)程, 水稻土中的三價(jià)鐵離子(FeⅢ)在其中扮演了重要的角色, 為硫酸鹽還原菌提供了電子受體, 增強(qiáng)了稻田土壤中無(wú)機(jī)汞的甲基化能力[33]。

2 汞暴露風(fēng)險(xiǎn)評(píng)估

汞礦區(qū)汞污染傳播及居民汞暴露途徑很多且復(fù)雜, 食用種植在汞污染土壤上的農(nóng)作物, 是人體汞暴露的重要途徑之一。同時(shí), 汞礦區(qū)高濃度大氣汞背景值和高含量汞的水體, 通過(guò)呼吸、飲食直接接觸, 也可以進(jìn)入礦區(qū)居民體內(nèi)。因此, 汞礦區(qū)人群或直接吸入大氣汞和水中的汞, 或通過(guò)食物鏈的傳輸, 食用汞污染的蔬菜、谷物和豬、魚(yú)、牛、雞等攝食汞污染的牧草、蔬菜、飼料、谷物的動(dòng)物, 導(dǎo)致人體內(nèi)汞的攝入。

風(fēng)險(xiǎn)評(píng)估, 是評(píng)估人體暴露在危險(xiǎn)因子下, 可能引起健康危害的機(jī)率, 結(jié)合了危害鑒定、劑量效應(yīng)評(píng)估和暴露評(píng)估的風(fēng)險(xiǎn)度量化結(jié)果。本文風(fēng)險(xiǎn)評(píng)估使用的參數(shù)及設(shè)定說(shuō)明具體如下。

2.1 假設(shè)條件

僅考慮由汞礦生產(chǎn)活動(dòng)造成的汞污染所產(chǎn)生的風(fēng)險(xiǎn), 不考慮其他環(huán)境污染所造成的風(fēng)險(xiǎn)。同時(shí), 由于汞礦區(qū)多為自給自足型經(jīng)濟(jì), 居民的一日三餐均以自產(chǎn)稻米和蔬菜為主體飲食, 故設(shè)定汞礦區(qū)居民所食用的稻米、蔬菜、魚(yú)、肉類(lèi)等的食物皆為礦區(qū)內(nèi)生產(chǎn)。

2.2 暴露途徑

汞礦區(qū)居民的汞暴露主要途徑包括直接吸入、農(nóng)產(chǎn)品攝入和畜產(chǎn)品攝入等。但是影響礦區(qū)居民人體汞暴露的因素很多。食物鏈中的飲食結(jié)構(gòu)是影響人體通過(guò)腸胃吸收汞的重要因素, 飲食結(jié)構(gòu)不同, 汞的攝入量各異。同時(shí), 通過(guò)飲食進(jìn)入人體中的汞, 不同形態(tài)汞的吸收率不同。具有很強(qiáng)的親脂性的甲基汞, 一旦進(jìn)入人體便可以100%被吸收; 無(wú)機(jī)汞不同, 進(jìn)入人體后只有極少部分會(huì)通過(guò)腸胃被吸收, 通常被人體吸收的比率為7%~8%[12]。

高濃度大氣汞暴露的影響因素, 包括了季節(jié)、溫度的變化、生活區(qū)域、個(gè)體代謝以及大氣中的汞形態(tài)等。人體大氣汞的日暴露量, 取決于個(gè)體日吸入大氣的總量。通常, 成年人平均吸入的大氣的速率接近0.83 m3/h, 約20 m3/d。通過(guò)呼吸進(jìn)入肺部的大氣汞, 被吸收進(jìn)入人體的比率約60%~80%[34]。

2.3 汞暴露量的計(jì)算

以表1中的空氣及食物中汞的含量, 并參考汞礦區(qū)最新文獻(xiàn)中報(bào)道的數(shù)據(jù), 據(jù)以估算汞礦區(qū)居民汞的日暴露量。依據(jù)前述結(jié)果及假設(shè)條件, 分別計(jì)算傳輸介質(zhì)中汞的含量, 由于國(guó)內(nèi)對(duì)于風(fēng)險(xiǎn)評(píng)估的研究尚處于起步階段, 本估算中所采用的計(jì)算公式參考美國(guó)環(huán)保署資料[35–36]。計(jì)算公式如下:

式中:為終生平均日暴露量, 單位μg/(kg·d);為不同介質(zhì)中汞的含量;為攝入量(暴露因子);和為接觸頻率與暴露周期;為平均體重;為終生天數(shù)(365 d/a)。

式(1)中的攝入量(暴露因子)、接觸頻率、暴露周期、人體平均體重以及終生天數(shù)等風(fēng)險(xiǎn)評(píng)估設(shè)定的暴露途徑參數(shù)見(jiàn)表2。其中, 農(nóng)產(chǎn)品及畜產(chǎn)品食入量、平均體重引用我國(guó)的統(tǒng)計(jì)值; 接觸頻率、暴露周期等參數(shù)設(shè)定礦區(qū)居民終生未有遷棲而生活于礦區(qū)內(nèi); 其他參數(shù)參考有關(guān)文獻(xiàn)。

2.4 風(fēng)險(xiǎn)因子的計(jì)算

汞礦區(qū)居民汞的日暴露量估算后, 以日暴露量()和糧農(nóng)組織/世界衛(wèi)生組織食品添加劑聯(lián)合專(zhuān)家委員會(huì)[37–38]推薦的無(wú)機(jī)汞和甲基汞的日安全攝入量()進(jìn)行風(fēng)險(xiǎn)因子()的計(jì)算。計(jì)算公式如下:

式中:為風(fēng)險(xiǎn)因子;為日暴露量;為安全攝入量。

式(2)中汞的安全攝入量包括無(wú)機(jī)汞和甲基汞, 其中無(wú)機(jī)汞的日安全攝入量為0.57 μg/(kg·d), 甲基汞的日安全攝入量為0.23 μg/(kg·d)。

表2?汞礦區(qū)居民健康風(fēng)險(xiǎn)評(píng)估汞暴露途徑參數(shù)統(tǒng)計(jì)

2.5 結(jié)果與討論

據(jù)前述參數(shù), 用式(1)和式(2)對(duì)我國(guó)汞礦區(qū)居民不同汞暴露途徑日暴露量進(jìn)行估算, 并計(jì)算風(fēng)險(xiǎn)因子。風(fēng)險(xiǎn)評(píng)估結(jié)果見(jiàn)表3。

表3數(shù)據(jù)顯示, 汞礦區(qū)居民通過(guò)蔬菜和稻米進(jìn)食而產(chǎn)生無(wú)機(jī)汞的暴露最高, 平均日暴露量分別為0.13 μg/kg和0.10 μg/kg, 占無(wú)機(jī)汞總暴露的80%以上, 導(dǎo)致的風(fēng)險(xiǎn)因子分別為0.23和0.18; 它們產(chǎn)生的最大暴露量分別可達(dá)0.48 μg/kg和0.89 μg/kg, 其中稻米進(jìn)食導(dǎo)致的風(fēng)險(xiǎn)因子為1.6。與無(wú)機(jī)汞暴露不同, 稻米進(jìn)食產(chǎn)生的甲基汞暴露量遠(yuǎn)遠(yuǎn)高出了其他的進(jìn)食途徑, 平均甲基汞的日暴露量0.16 μg/kg, 但其最大暴露量卻高達(dá)1.9 μg/kg, 表現(xiàn)出了很高的風(fēng)險(xiǎn)因子, 高達(dá)8.1。盡管各暴露途徑的均值評(píng)估數(shù)據(jù)均未超出JECFA[35–36]和USEPA[37–38]推薦的建議值, 但各進(jìn)食途徑產(chǎn)生的總暴露量(包括無(wú)機(jī)汞和甲基汞), 導(dǎo)致的風(fēng)險(xiǎn)因子已經(jīng)超過(guò)了1.0。通常風(fēng)險(xiǎn)因子小于1時(shí), 不會(huì)對(duì)人體造成危害; 當(dāng)風(fēng)險(xiǎn)因子大于1時(shí), 將會(huì)有可能導(dǎo)致健康風(fēng)險(xiǎn)[35,36,39]。

以上數(shù)據(jù)表明, 汞礦區(qū)生活人群已經(jīng)存在著汞暴露的潛在健康風(fēng)險(xiǎn)。已報(bào)道的調(diào)查結(jié)果亦顯示, 汞礦區(qū)居民頭發(fā)中總汞和甲基汞含量高達(dá)210 mg/kg和5.9 mg/kg, 遠(yuǎn)遠(yuǎn)高于對(duì)照區(qū)人群[23,24,40], 而且頭發(fā)甲基汞含量與進(jìn)食稻米的量呈顯著正相關(guān)性[22]; 稻米進(jìn)食暴露實(shí)驗(yàn)表明, 實(shí)驗(yàn)動(dòng)物白鼠進(jìn)食汞礦區(qū)生產(chǎn)的大米20 d后, 它們的腦、肝組織產(chǎn)生了顯著的變化, 汞含量明顯升高[41–43], 表現(xiàn)出了明顯的汞積累特征。這些結(jié)果顯示稻米已經(jīng)成為汞礦區(qū)人群的甲基汞暴露的最主要途徑, 對(duì)人體已造成了潛在的健康風(fēng)險(xiǎn)。由于稻米是當(dāng)?shù)鼐用竦闹魇?因此汞礦區(qū)高含量汞稻米尤其是甲基汞污染稻米, 對(duì)人體健康的影響是不容忽視的。

表3 我國(guó)汞礦區(qū)居民汞暴露日平均風(fēng)險(xiǎn)值評(píng)估結(jié)果

3?展?望

環(huán)境汞污染問(wèn)題是許多國(guó)家面臨的重要環(huán)境問(wèn)題, 以往研究?jī)H關(guān)注汞對(duì)水生生態(tài)系統(tǒng)魚(yú)體汞污染的研究。但是汞礦山汞污染土壤種植水稻的甲基汞污染問(wèn)題, 已引起了關(guān)注[33,44,45], 加強(qiáng)對(duì)汞礦區(qū)水稻富集甲基汞的機(jī)理的研究, 將成為環(huán)境汞污染研究領(lǐng)域的前沿科學(xué)問(wèn)題。我國(guó)汞礦山的環(huán)境汞污染問(wèn)題已非常突出, 對(duì)礦區(qū)汞污染環(huán)境的修復(fù)技術(shù)的研發(fā), 尤其是解決稻米甲基汞污染問(wèn)題, 必將成為環(huán)境科學(xué)研究的重要科學(xué)技術(shù)問(wèn)題之一。已有的研究結(jié)果顯示, 成本較低且對(duì)生態(tài)環(huán)境的影響較小的植物修復(fù), 可能會(huì)成為礦區(qū)汞污染環(huán)境修復(fù)的重要可行的手段[46]。

汞暴露對(duì)人體及動(dòng)物健康影響的研究已取得了長(zhǎng)足進(jìn)展, 但是目前對(duì)長(zhǎng)期的和低劑量的不同形態(tài)汞暴露, 以及其對(duì)人體健康影響的研究有待于深入研究。目前研究的對(duì)象主要集中在以食魚(yú)和其他水產(chǎn)品暴露甲基汞的人群, 但由于魚(yú)和水產(chǎn)品中富含益于大腦發(fā)育的微量物質(zhì), 如多聚不飽和脂肪酸(n-3 LCPUFA)、膽堿、碘、鐵等[47–49], 這與稻米的甲基汞污染問(wèn)題顯著不同。因此, 對(duì)食用稻米產(chǎn)生的甲基汞暴露以及由此導(dǎo)致的健康風(fēng)險(xiǎn)的研究, 可為認(rèn)識(shí)長(zhǎng)期、低劑量甲基汞暴露對(duì)人體健康影響提供新的認(rèn)識(shí)。

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Risk assessments and exposure pathways of inorganic mercury and methylmercury to populations from mercury mining regions in China

FENG Xin-bin1*, QIU Guang-le1, WANG Shao-feng1,2, LI Ping1and MENG Bo1

1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang?550002, China; 2. Key Laboratory of Terrestrial Ecological Processes, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang?110016, China

Mercury (Hg) pollution and human health risks resulted from Hg mining poses more concerns worldwide. Routes of the daily Hg uptakes in the local populations include contaminated air inhaling, water drinking, and contaminated food consumption. The risk assessment shows that the dominant pathways of exposure to inorganic Hg for the local residents are rice and vegetables, with a high average daily uptake of 0.10 μg/kg for rice and of 0.13 μg/kg for vegetables, respectively, which counts for > 80 percentage of the total inorganic Hg exposure. Unlikely, the daily uptake of methylmercury (MeHg) through rice consumption was elevated compared to other foods consumption, such as vegetables, fish, and water drinking. A high hazard index (HI) of 8.1 was presented in rice, with an elevated uptake of 1.9 μg/kg. Although the average daily intakes of both inorganic Hg and MeHg through entire compartments investigated did not exceed 0.57 μg/(kg·d) for inorganic Hg and 0.23 μg/(kg·d) for MeHg recommended by JECFA, the total amount of both daily inorganic Hg uptake and daily MeHg uptake exhibited a HI value of >1.0, indicating that the present high Hg concentrations in foodstuff might result in an undesirable Hg exposure to residents, especially the susceptible populations, such as pregnants and infants.

mercury; environmental pollution; exposure pathway; risk assessment; mercury mining areas

P595

A

0379-1726(2013)03-0205-07

2013-01-30;

2013-02-05;

2013-02-05

國(guó)家自然科學(xué)基金(41173126)

馮新斌(1968–), 男, 研究員, 地球化學(xué)專(zhuān)業(yè)。

FENG Xin-bin, E-mail: fengxinbin@vip.skleg.cn, Tel: +86-851-5895728