溫(wen)石棉塊體通常為(wei)不同(tong)(tong)色(se)調的綠色(se)及黃(huang)色(se),也有(you)(you)的為(wei)白色(se)。劈分后的絲狀纖(xian)(xian)維(wei)為(wei)白色(se),絲絹光澤(ze);硬度(du)2~2.5;理論密(mi)度(du)為(wei)2.56g/cm3,化學成分中類質同(tong)(tong)象代替,決定(ding)實(shi)(shi)際(ji)密(mi)度(du)值的大小,Fe、Ti、Mn、Ni等(deng)元素取代Mg時,密(mi)度(du)偏大,Al、Ti取代Si時,密(mi)度(du)偏小,與纖(xian)(xian)維(wei)管心(xin)有(you)(you)無(wu)充填物(wu)也有(you)(you)關系,實(shi)(shi)際(ji)密(mi)度(du)為(wei)2.426~2.646 g/cm3。
溫石(shi)棉的(de)光學(xue)性質
溫(wen)石棉(mian)的光學(xue)性(xing)質,折射率Ng為(wei)(wei)1.534~1.555,Np為(wei)(wei)1.522~1.549,Ng值(zhi)隨Fe2O3及FeO含(han)量增(zeng)多(duo)(duo)而增(zeng)大,Np值(zhi)隨FeO及H2O+含(han)量增(zeng)多(duo)(duo)而增(zeng)大;多(duo)(duo)色(se)性(xing),Ng為(wei)(wei)各種色(se)調(diao)的綠色(se),Np為(wei)(wei)各種色(se)調(diao)的黃色(se);平行消光,正(zheng)延性(xing)為(wei)(wei)主。
衍射特征
溫(wen)石(shi)棉的X射線衍(yan)射特征,有(you)兩條(tiao)強衍(yan)射線,d(002)為(wei)0.728~0.740nm和d(004)為(wei)0.369~0.366nm;另有(you)四條(tiao)中(zhong)強衍(yan)射線,d(020)為(wei)0.437~0.459nm、d(201)為(wei)0.256~0.260nm、d(202)為(wei)0.243~0.248nm、d(402)為(wei)0.130~0.134nm。溫(wen)石(shi)棉在自然界產出以2Mc型纖(xian)蛇(she)紋(wen)石(shi)最多(duo),ZORc型正纖(xian)蛇(she)紋(wen)石(shi)少(shao)見(jian)。
溫石棉的熱效應
溫石棉的熱(re)(re)效(xiao)應(ying)(ying),在670~730℃區間(jian)(jian)出現深而大(da)的放熱(re)(re)效(xiao)應(ying)(ying)(吸熱(re)(re)谷(gu)或脫羥谷(gu));815~830℃區間(jian)(jian)出現矮而窄的放熱(re)(re)效(xiao)應(ying)(ying)(熱(re)(re)放峰),原礦物結(jie)構被徹底破壞,形成(cheng)新的物相(xiang),即(ji)鎂橄欖石和頑(wan)輝石的混合相(xiang)。
溫石棉的(de)紅外光譜
溫(wen)石棉(mian)的紅外光譜(pu),不同(tong)結晶程度的溫(wen)石棉(mian),主要表現在1100~950cm-1三個方向的Si—O伸縮振(zhen)動帶及3700~3600cm-1羥基吸收振(zhen)動的差別。
溫石棉(mian)的(de)電子顯微像多為空心(xin)管狀(zhuang),其內徑一般為6~8nm,外徑為20~50nm。
溫石棉的理論化學成(cheng)分
SiO2 43.36%、MgO43.64%、H2O+13%。一般含有Fe2O3、FeO、TiO2、Al2O3、MnO、CaO、K2O、Na2O、Cr2O3、V2O5、NiO、F-、Cl等雜質(zhi)。表(biao)明混有磁鐵礦、方解石(shi)(shi)、白云(yun)石(shi)(shi)、菱(ling)鎂礦、水滑石(shi)(shi)、石(shi)(shi)英、水鎂石(shi)(shi)、鉻尖晶石(shi)(shi)等雜質(zhi)礦物或元素的類質(zhi)同象取代。
溫石棉具有多種(zhong)物理化學性質,劈(pi)分(fen)性能(neng)優良,能(neng)最大限度地劈(pi)分(fen)為絲狀體,劈(pi)分(fen)直(zhi)徑最小為1~2μm。工業(ye)利用以比表(biao)面積為衡量指標,一般在(zai)5~50m2/g。機械(xie)強度高,抗張(zhang)強度值為120~350(單位(wei)9.8×106Pa)。
其中:高強(qiang)(qiang)(qiang)度(du)(du)(du)纖(xian)維(wei)(wei)(wei)(wei)大于(yu)350,正常(chang)強(qiang)(qiang)(qiang)度(du)(du)(du)纖(xian)維(wei)(wei)(wei)(wei)小于(yu)350、大于(yu)250,中等(deng)強(qiang)(qiang)(qiang)度(du)(du)(du)纖(xian)維(wei)(wei)(wei)(wei)小于(yu)250、大于(yu)150,低強(qiang)(qiang)(qiang)度(du)(du)(du)纖(xian)維(wei)(wei)(wei)(wei)小于(yu)150。溫(wen)石(shi)(shi)棉纖(xian)維(wei)(wei)(wei)(wei)強(qiang)(qiang)(qiang)度(du)(du)(du)優于(yu)角(jiao)閃石(shi)(shi)類(lei)石(shi)(shi)棉及(ji)人造碳(tan)纖(xian)維(wei)(wei)(wei)(wei),與硼纖(xian)維(wei)(wei)(wei)(wei)和玻(bo)璃纖(xian)維(wei)(wei)(wei)(wei)接近。耐熱(re)(re)性(xing)(xing)能良好(hao),工(gong)業(ye)利用溫(wen)度(du)(du)(du)可達(da)500℃(熱(re)(re)失重(zhong)率小于(yu)1%)。溫(wen)石(shi)(shi)棉耐堿腐(fu)蝕(shi)(shi)性(xing)(xing)強(qiang)(qiang)(qiang),堿蝕(shi)(shi)量(liang)為(wei)0.46%~0.74%,耐酸腐(fu)蝕(shi)(shi)性(xing)(xing)差(cha),不如角(jiao)閃石(shi)(shi)石(shi)(shi)棉,酸蝕(shi)(shi)量(liang)一(yi)般為(wei)55%~58%。隔熱(re)(re)性(xing)(xing)能和導熱(re)(re)性(xing)(xing)能好(hao),導熱(re)(re)系數一(yi)般為(wei)0.121~0.227W/(m·K)。電(dian)絕緣(yuan)性(xing)(xing)良好(hao),電(dian)阻率ρ一(yi)般為(wei)0.6×108~4×108Ω·cm。
溫石棉纖(xian)維還具(ju)有過濾性[透過系數(shu)為(wei)(wei)(wei)15%~60%,阻力為(wei)(wei)(wei)0.4×9.8~13.9×9.8Pa]、成膜打(da)漿性、磁(ci)性(雙磁(ci)化系數(shu)為(wei)(wei)(wei)6×10^-6~10×10^-6cm/g)、電動電位(一(yi)般e>20mV)等。
石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)有致癌性早已為相關行業周(zhou)知,但石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)細分為溫石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)和(he)閃石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)。經中外多(duo)(duo)(duo)(duo)位礦物(wu)學(xue)、病理(li)學(xue)、毒(du)性學(xue)專家學(xue)者(zhe)在長(chang)達(da)2年(nian)多(duo)(duo)(duo)(duo)的(de)比較(jiao)試(shi)驗證明,在溫石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)、閃石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)及其他多(duo)(duo)(duo)(duo)種“溫石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)替代纖(xian)維(wei)”中,溫石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)是相對最(zui)安全(quan)的(de)無(wu)機纖(xian)維(wei)材料。自從2004年(nian),瑞士(shi)著名的(de)吸入毒(du)物(wu)專家、多(duo)(duo)(duo)(duo)國(guo)(guo)政府(fu)毒(du)物(wu)學(xue)顧問大衛·伯(bo)恩斯(si)坦(tan)(tan)博士(shi)公布“溫石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)(mian)可(ke)以安全(quan)使用(yong)”的(de)實(shi)驗結(jie)(jie)果之后(hou),2年(nian)來,中國(guo)(guo)、俄羅斯(si)、加(jia)拿大、印度、巴西(xi)、墨(mo)西(xi)哥等國(guo)(guo)多(duo)(duo)(duo)(duo)位礦物(wu)學(xue)、病理(li)學(xue)、毒(du)性學(xue)專家,經過(guo)各(ge)自的(de)科學(xue)實(shi)驗,得出與伯(bo)恩斯(si)坦(tan)(tan)博士(shi)完全(quan)一致的(de)結(jie)(jie)論。
然而,2001年三月(yue)WTO做出具(ju)有(you)(you)里程碑(bei)意義的(de)裁定,認(ren)(ren)為(wei)溫石棉(mian)(mian)既然已被(bei)認(ren)(ren)定是致(zhi)癌物質(zhi)(zhi),石棉(mian)(mian)生(sheng)產商(shang)堅(jian)持(chi)的(de)安全(quan)使(shi)用(yong)極限就不存在。使(shi)得(de)WTO的(de)各個成(cheng)員國(guo)禁止使(shi)用(yong)或(huo)進口如(ru)石棉(mian)(mian)等含致(zhi)癌物質(zhi)(zhi)的(de)權利合法化,也進一步確認(ren)(ren)WTO各成(cheng)員國(guo)有(you)(you)權認(ren)(ren)為(wei)保護生(sheng)命(ming)和健康比履行貿易義務更為(wei)重要(yao)。
石(shi)棉(mian)(mian)的致癌性早已被學界所知,但(dan)國內(nei)行業,特別是(shi)建筑(zhu)行業并沒有禁用(yong),政(zheng)府雖然(ran)規定了開采加工溫(wen)石(shi)棉(mian)(mian)必須佩(pei)戴防護(hu)用(yong)品,但(dan)對(dui)于應(ying)用(yong)并沒有給(gei)出相應(ying)規范和(he)引導。
石(shi)(shi)(shi)(shi)棉分(fen)為蛇(she)紋石(shi)(shi)(shi)(shi)石(shi)(shi)(shi)(shi)棉(溫(wen)石(shi)(shi)(shi)(shi)棉)和角閃石(shi)(shi)(shi)(shi)類石(shi)(shi)(shi)(shi)棉(青石(shi)(shi)(shi)(shi)棉、陽起(qi)石(shi)(shi)(shi)(shi)石(shi)(shi)(shi)(shi)棉、直(zhi)閃石(shi)(shi)(shi)(shi)石(shi)(shi)(shi)(shi)棉、鐵石(shi)(shi)(shi)(shi)棉、透閃石(shi)(shi)(shi)(shi)石(shi)(shi)(shi)(shi)棉)兩類。中(zhong)國石(shi)(shi)(shi)(shi)棉資源(yuan)絕大部(bu)分(fen)為溫(wen)石(shi)(shi)(shi)(shi)棉礦,溫(wen)石(shi)(shi)(shi)(shi)棉 占石(shi)(shi)(shi)(shi)棉總產量的(de)95%以上。石(shi)(shi)(shi)(shi)棉使(shi)用的(de)安全性(xing)是礦物工業產業一個(ge)具有(you)(you)爭議性(xing)的(de)話題。石(shi)(shi)(shi)(shi)棉所致職業病中(zhong)對(dui)(dui)人體危(wei)害最嚴(yan)重的(de)是石(shi)(shi)(shi)(shi)棉肺、肺癌以及間皮瘤(liu)。在(zai)所有(you)(you)種類石(shi)(shi)(shi)(shi)棉中(zhong),致病能力(li)最強的(de)是青石(shi)(shi)(shi)(shi)棉,對(dui)(dui)于(yu)溫(wen)石(shi)(shi)(shi)(shi)棉潛在(zai)致癌、致纖維化的(de)能力(li)還存在(zai)爭議。
溫石棉(mian)的致癌和致纖維(wei)化機(ji)制
溫石(shi)棉同其他種類石(shi)棉的(de)致病機制(zhi)(zhi)大(da)致相同,其危害(hai)來自加工時產生(sheng)的(de)粉塵纖(xian)(xian)(xian)維。這(zhe)些細(xi)小(xiao)的(de)纖(xian)(xian)(xian)維通過(guo)呼吸進(jin)入(ru)肺內(nei),大(da)部分經呼吸道的(de)廓清體(ti)系(黏液纖(xian)(xian)(xian)毛廓清機制(zhi)(zhi)和有效的(de)咳嗽)排(pai)出(chu)體(ti)外,如果(guo)不能排(pai)出(chu),可被(bei)肺泡巨(ju)噬(shi)細(xi)胞(bao)所(suo)吞噬(shi)或(huo)穿(chuan)透上皮細(xi)胞(bao)而進(jin)入(ru)肺間(jian)質,從而在(zai)體(ti)內(nei)持續停留很長(chang)時間(jian)。滯留的(de)溫石(shi)棉纖(xian)(xian)(xian)維引發(fa)炎(yan)癥(zheng)反應(ying)和氧化(hua)應(ying)激(ji)反應(ying),這(zhe)是石(shi)棉致細(xi)胞(bao)損傷的(de)重(zhong)要機制(zhi)(zhi)。目前溫石(shi)棉致纖(xian)(xian)(xian)維化(hua)和致癌的(de)機制(zhi)(zhi)仍未充(chong)分闡明,主要認為包含以下(xia)機制(zhi)(zhi):
1)機械(xie)損(sun)傷:溫石棉多數以(yi)元纖(xian)維的形(xing)態(tai)侵(qin)入人體,這(zhe)類纖(xian)維為結晶(jing)態(tai),銳利并(bing)有尖刺,可以(yi)刺破肺泡上皮細胞(bao)和(he)(he)胸(xiong)膜間(jian)皮細胞(bao),對染色體和(he)(he)DNA造成機械(xie)干擾和(he)(he)損(sun)傷,導(dao)致肺癌和(he)(he)間(jian)皮瘤(liu)發生。
2)自(zi)(zi)由(you)(you)基和(he)(he)(he)(he)細(xi)(xi)(xi)胞(bao)(bao)(bao)因(yin)子介導(dao)的(de)(de)(de)損(sun)傷(shang):溫(wen)石棉(mian)(mian)纖(xian)(xian)維(wei)(wei)基于自(zi)(zi)身的(de)(de)(de)化(hua)學特性(xing)和(he)(he)(he)(he)通(tong)過(guo)激(ji)活(huo)肺泡巨(ju)噬(shi)細(xi)(xi)(xi)胞(bao)(bao)(bao),可(ke)(ke)以誘導(dao)過(guo)氧(yang)(yang)化(hua)氫、超氧(yang)(yang)化(hua)物陰(yin)離子和(he)(he)(he)(he)氫氧(yang)(yang)根離子等活(huo)性(xing)氧(yang)(yang)的(de)(de)(de)產生(sheng),導(dao)致(zhi)(zhi)DNA損(sun)傷(shang)和(he)(he)(he)(he)纖(xian)(xian)維(wei)(wei)化(hua)。一方面(mian)溫(wen)石棉(mian)(mian)纖(xian)(xian)維(wei)(wei)表(biao)(biao)面(mian)存(cun)在(zai)(zai)(zai)的(de)(de)(de)不飽和(he)(he)(he)(he)O-Si-O、Si-O-Si和(he)(he)(he)(he)Mg-O鍵等,具有(you)很(hen)強的(de)(de)(de)表(biao)(biao)面(mian)活(huo)性(xing),含氧(yang)(yang)自(zi)(zi)由(you)(you)基引(yin)起(qi)(qi)細(xi)(xi)(xi)胞(bao)(bao)(bao)膜(mo)自(zi)(zi)由(you)(you)基的(de)(de)(de)鏈(lian)式反應(ying);另一方面(mian)溫(wen)石棉(mian)(mian)還可(ke)(ke)通(tong)過(guo)刺(ci)激(ji)巨(ju)噬(shi)細(xi)(xi)(xi)胞(bao)(bao)(bao)發生(sheng)呼(hu)吸爆發及(ji)(ji)崩(beng)解(jie)死亡,釋放(fang)一系列溶酶(mei)體(ti)(ti)(ti)酶(mei)、炎性(xing)細(xi)(xi)(xi)胞(bao)(bao)(bao)因(yin)子及(ji)(ji)活(huo)性(xing)氧(yang)(yang)自(zi)(zi)由(you)(you)基。在(zai)(zai)(zai)兩(liang)種(zhong)機制作(zuo)用(yong)下,細(xi)(xi)(xi)胞(bao)(bao)(bao)膜(mo)上多聚不飽和(he)(he)(he)(he)脂(zhi)肪酸發生(sheng)脂(zhi)質(zhi)過(guo)氧(yang)(yang)化(hua)反應(ying),引(yin)起(qi)(qi)細(xi)(xi)(xi)胞(bao)(bao)(bao)和(he)(he)(he)(he)基質(zhi)損(sun)傷(shang)。溫(wen)石棉(mian)(mian)纖(xian)(xian)維(wei)(wei)通(tong)過(guo)對巨(ju)噬(shi)細(xi)(xi)(xi)胞(bao)(bao)(bao)和(he)(he)(he)(he)成纖(xian)(xian)維(wei)(wei)細(xi)(xi)(xi)胞(bao)(bao)(bao)的(de)(de)(de)細(xi)(xi)(xi)胞(bao)(bao)(bao)膜(mo)的(de)(de)(de)脂(zhi)質(zhi)過(guo)氧(yang)(yang)化(hua)作(zuo)用(yong),引(yin)起(qi)(qi)細(xi)(xi)(xi)胞(bao)(bao)(bao)和(he)(he)(he)(he)基質(zhi)成分損(sun)傷(shang),促進成纖(xian)(xian)維(wei)(wei)細(xi)(xi)(xi)胞(bao)(bao)(bao)增殖和(he)(he)(he)(he) 膠(jiao)原合成,導(dao)致(zhi)(zhi)整個(ge)肺泡結構(gou)單(dan)位破壞,形成不可(ke)(ke)逆的(de)(de)(de)纖(xian)(xian)維(wei)(wei)化(hua),即石棉(mian)(mian)肺等肺部(bu)纖(xian)(xian)維(wei)(wei)化(hua)疾病(bing)。溫(wen)石棉(mian)(mian)纖(xian)(xian)維(wei)(wei)所致(zhi)(zhi)遺傳毒性(xing)早(zao)期改變(bian)主要通(tong)過(guo)DNA損(sun)傷(shang)和(he)(he)(he)(he)染色體(ti)(ti)(ti)改變(bian)途(tu)徑(jing)。在(zai)(zai)(zai)DNA層(ceng)面(mian),主要通(tong)過(guo)DNA單(dan)鏈(lian)、雙鏈(lian)斷(duan)裂、氧(yang)(yang)化(hua)損(sun)傷(shang)等途(tu)徑(jing)引(yin)起(qi)(qi)細(xi)(xi)(xi)胞(bao)(bao)(bao)致(zhi)(zhi)突變(bian)性(xing)。在(zai)(zai)(zai)染色體(ti)(ti)(ti)層(ceng)面(mian),主要通(tong)過(guo)使染色體(ti)(ti)(ti)或染色體(ti)(ti)(ti)單(dan)體(ti)(ti)(ti)發生(sheng)斷(duan)裂、缺失、 倒位以及(ji)(ji)姐妹染色體(ti)(ti)(ti)單(dan)體(ti)(ti)(ti)互換等,引(yin)起(qi)(qi)染色體(ti)(ti)(ti)畸變(bian)或數目改變(bian),從而產生(sheng)致(zhi)(zhi)突變(bian)作(zuo)用(yong)。
3)原癌(ai)(ai)基因激活和抑癌(ai)(ai)基因失活:溫石棉可以改(gai)變細胞信(xin)號傳導(dao)系(xi)統(tong),激活原癌(ai)(ai)基因并導(dao)致抑癌(ai)(ai)基因失活,進而影響細胞的(de)增殖和分化,引起肺(fei)癌(ai)(ai)和間皮瘤的(de)發生。
溫石棉致(zhi)病性的影響因素
濃度(du)對溫石棉致病性的影響
國內(nei)(nei)外研究(jiu)認(ren)為(wei)作業環境(jing)空(kong)(kong)氣中溫(wen)石(shi)(shi)棉(mian)粉(fen)塵質量(liang)濃度(du)(以(yi)下簡稱濃度(du))與石(shi)(shi)棉(mian)肺(fei)發病(bing)有(you)明顯的(de)(de)(de)(de)劑量(liang)反應關系(xi),它在(zai)空(kong)(kong)氣中的(de)(de)(de)(de)含量(liang)必須達到一(yi)定程度(du),才(cai)會(hui)對(dui)人(ren)體(ti)健(jian)康造成危(wei)害(hai)。各研究(jiu)分別按1%~3%石(shi)(shi)棉(mian)肺(fei)患病(bing)率、30~40年工(gong)作年限計(ji)算(suan),預測石(shi)(shi)棉(mian)粉(fen)塵容許濃度(du)應低(di)(di)于2.71~3.90mg/m3或石(shi)(shi)棉(mian)纖(xian)維(wei)容許濃度(du)應低(di)(di)于1.15 ~2.00f/mL(f為(wei)纖(xian)維(wei)根(gen)數),說明中國現行工(gong)作場所(suo)石(shi)(shi)棉(mian)粉(fen)塵職業接觸(chu)限值(zhi)0.8mg/m3或0.8f/mL是合理(li)的(de)(de)(de)(de),溫(wen)石(shi)(shi)棉(mian)纖(xian)維(wei)的(de)(de)(de)(de)濃度(du)可以(yi)被控(kong)制(zhi)在(zai)安(an)全范圍內(nei)(nei)。同時也有(you)學者認(ren)為(wei)在(zai)溫(wen)石(shi)(shi)棉(mian)接觸(chu)水(shui)平低(di)(di)的(de)(de)(de)(de)人(ren)群中一(yi)直觀察到致癌風險的(de)(de)(de)(de)增加,因此溫(wen)石(shi)(shi)棉(mian)沒有(you)一(yi)定的(de)(de)(de)(de)安(an)全閾值(zhi)。這(zhe)是部分研究(jiu)人(ren)員認(ren)為(wei)溫(wen)石(shi)(shi)棉(mian)沒有(you)安(an)全閾值(zhi)的(de)(de)(de)(de)原因。
形態對(dui)溫石(shi)棉(mian)致病性的影(ying)響(xiang)
纖維尺寸影響(xiang)(xiang)生物(wu)殘存性(xing),進(jin)而影響(xiang)(xiang)肺(fei)的呼吸、沉淀和(he)清(qing)除。主要從兩個方面考慮尺寸的影響(xiang)(xiang):
1)纖維(wei)是否可吸(xi)入;
2)如(ru)果它(ta)處(chu)于(yu)(yu)可(ke)吸入的(de)(de)(de)尺寸,吸入肺(fei)后(hou)仍需(xu)考(kao)慮纖(xian)(xian)維(wei)尺寸的(de)(de)(de)影(ying)響。大多(duo)數溫(wen)石(shi)(shi)棉纖(xian)(xian)維(wei)和粉塵(chen)可(ke)被(bei)(bei)氣管—支氣管樹的(de)(de)(de)黏液逐步向上運(yun)移并隨咳(ke)嗽(sou)排(pai)出,據病(bing)(bing)理學標本電(dian)鏡檢測,肺(fei)部(bu)沒有發現過(guo)長(chang)(chang)(chang)度大于(yu)(yu)200μm的(de)(de)(de)纖(xian)(xian)維(wei),多(duo)數短(duan)于(yu)(yu)50μm。進入肺(fei)部(bu)后(hou),尺寸很(hen)短(duan)的(de)(de)(de)纖(xian)(xian)維(wei),尤其那些短(duan)于(yu)(yu)5μm的(de)(de)(de)纖(xian)(xian)維(wei)和粉塵(chen),能夠被(bei)(bei)巨噬細胞完全(quan)吞噬,通(tong)過(guo)類似(si)非纖(xian)(xian)維(wei)顆粒物的(de)(de)(de)清(qing)除機制被(bei)(bei)清(qing)除,較長(chang)(chang)(chang)的(de)(de)(de)纖(xian)(xian)維(wei)不能被(bei)(bei)巨噬細胞完全(quan)吞沒,長(chang)(chang)(chang)時間(jian)(jian)存(cun)在肺(fei)內將(jiang)導致(zhi)(zhi)疾病(bing)(bing)。而更(geng)長(chang)(chang)(chang)的(de)(de)(de),長(chang)(chang)(chang)于(yu)(yu)20μm的(de)(de)(de)溫(wen)石(shi)(shi)棉纖(xian)(xian)維(wei)可(ke)以迅(xun)速從肺(fei)部(bu)被(bei)(bei)清(qing)除,不轉移到胸膜腔,不啟動(dong)纖(xian)(xian)維(wei)誘發的(de)(de)(de)反應。特別短(duan)的(de)(de)(de)可(ke)以吞食溶解,比較長(chang)(chang)(chang)的(de)(de)(de)可(ke)被(bei)(bei)清(qing)除,致(zhi)(zhi)病(bing)(bing)的(de)(de)(de)纖(xian)(xian)維(wei)集中于(yu)(yu)中間(jian)(jian)長(chang)(chang)(chang)度。對人(ren)體(ti)致(zhi)(zhi)癌危險性最大的(de)(de)(de)石(shi)(shi)棉纖(xian)(xian)維(wei)是長(chang)(chang)(chang)度大于(yu)(yu)5~8μm、直徑(jing)小于(yu)(yu)1.5μm或大于(yu)(yu)0.25μm的(de)(de)(de)纖(xian)(xian)維(wei)。
除了長度,纖(xian)(xian)維(wei)(wei)形狀(zhuang)也影(ying)響其(qi)(qi)致病性。角閃(shan)石(shi)(shi)石(shi)(shi)棉(mian)纖(xian)(xian)維(wei)(wei)是(shi)鏈(lian)狀(zhuang)結構,而溫石(shi)(shi)棉(mian)纖(xian)(xian)維(wei)(wei)是(shi)一種褶皺型的(de)或是(shi)卷成空(kong)心小(xiao)卷的(de)頁(ye)硅酸鹽,卷曲的(de)纖(xian)(xian)維(wei)(wei)形狀(zhuang)不(bu)易于吸入呼吸道。此外,薄而短的(de)纖(xian)(xian)維(wei)(wei)質量(liang)更(geng)小(xiao),比厚(hou)而長的(de)纖(xian)(xian)維(wei)(wei)在(zai)空(kong)氣中(zhong)懸浮(fu)(fu)的(de)時間更(geng)長。而大多數的(de)石(shi)(shi)棉(mian)纖(xian)(xian)維(wei)(wei)比目前正在(zai)開(kai)發的(de)新的(de)納米(mi)纖(xian)(xian)維(wei)(wei)更(geng)厚(hou),說明其(qi)(qi)懸浮(fu)(fu)時間更(geng)短,吸入可能(neng)性更(geng)小(xiao)。
可溶性(xing)與溫石(shi)棉致病性(xing)的影(ying)響(xiang)
在肺內沉(chen)積時,一些(xie)(xie)纖(xian)維(wei)能夠直接完全溶解(jie),另一些(xie)(xie)纖(xian)維(wei)不能溶解(jie),但可以(yi)斷(duan)裂成(cheng)短(duan)片后(hou)被成(cheng)功吞(tun)噬(shi)(shi)和清(qing)除(chu)。可溶性(xing)(xing)(xing)(xing)高的(de)(de)(de)(de)纖(xian)維(wei)表現較低(di)的(de)(de)(de)(de)致(zhi)病(bing)性(xing)(xing)(xing)(xing),而可溶性(xing)(xing)(xing)(xing)不佳的(de)(de)(de)(de)纖(xian)維(wei)致(zhi)病(bing)性(xing)(xing)(xing)(xing)較強。溫(wen)石(shi)(shi)(shi)棉(mian)可以(yi)被強酸(suan)(比如巨噬(shi)(shi)細胞吞(tun)噬(shi)(shi)時產(chan)生的(de)(de)(de)(de)酸(suan))分(fen)解(jie),有(you)更(geng)好的(de)(de)(de)(de)可溶解(jie)性(xing)(xing)(xing)(xing)以(yi)及更(geng)小的(de)(de)(de)(de)生物殘(can)存性(xing)(xing)(xing)(xing),這(zhe)將(jiang)減(jian)低(di)其對身體(ti)的(de)(de)(de)(de)致(zhi)病(bing)性(xing)(xing)(xing)(xing)。而角閃(shan)石(shi)(shi)(shi)類石(shi)(shi)(shi)棉(mian)更(geng)頑固(gu),在多數情況(kuang)下都不會(hui)被破(po)壞(huai)(huai),因此有(you)較強的(de)(de)(de)(de)致(zhi)癌性(xing)(xing)(xing)(xing)。溫(wen)石(shi)(shi)(shi)棉(mian)是一種片狀硅酸(suan)鹽(yan),呈薄層而卷曲的(de)(de)(de)(de)形態(tai),約0.8nm厚,是由鎂和二氧化(hua)硅組成(cheng)的(de)(de)(de)(de)夾層結構(gou)。肺 巨噬(shi)(shi)細胞提供的(de)(de)(de)(de)酸(suan)性(xing)(xing)(xing)(xing)環境可以(yi)快速破(po)壞(huai)(huai)這(zhe)種片狀結構(gou),將(jiang)溫(wen)石(shi)(shi)(shi)棉(mian)纖(xian)維(wei)分(fen)解(jie)成(cheng)小片,隨后(hou)這(zhe)些(xie)(xie)碎片可以(yi)很容易地從肺部清(qing)除(chu)。
角閃石類石棉(mian)是實(shi)心棒(bang)狀雙(shuang)鏈的四面體(ti)硅酸鹽纖(xian)維,這使得它(ta)非常結(jie)(jie)實(shi)耐用。角閃石類石棉(mian)晶體(ti)結(jie)(jie)構(gou)的外表面像石英(ying)一樣,并且具有類似(si)石英(ying)的耐化學性。角閃石類石棉(mian)纖(xian)維在任何pH值(zhi)下都不會溶(rong)解(jie)。
吸煙對溫石棉致病性的影響
煙(yan)(yan)草(cao)和(he)(he)石(shi)(shi)棉(mian)(mian)(mian)都是(shi)國(guo)際抗癌聯(lian)盟(meng)(IARC)宣(xuan)布(bu)的(de)人(ren)類(lei)致癌物,吸煙(yan)(yan)會對(dui)溫(wen)(wen)石(shi)(shi)棉(mian)(mian)(mian)接(jie)(jie)觸(chu)(chu)者(zhe)肺(fei)癌的(de)發生起協(xie)同(tong)作用。吸煙(yan)(yan)降低機(ji)體清(qing)除溫(wen)(wen)石(shi)(shi)棉(mian)(mian)(mian)纖(xian)維和(he)(he)粉塵(chen)(chen)的(de)功能(neng),使石(shi)(shi)棉(mian)(mian)(mian)塵(chen)(chen)易沉積于(yu)呼吸系統中,同(tong)時(shi)煙(yan)(yan)溶(rong)液抑(yi)制了巨(ju)噬細(xi)胞(bao)的(de)吞噬功能(neng),使巨(ju)噬細(xi)胞(bao)不能(neng)有效地防御侵襲(xi),從而使溫(wen)(wen)石(shi)(shi)棉(mian)(mian)(mian)直接(jie)(jie)作用于(yu)靶(ba)細(xi)胞(bao),加劇自(zi)由基(ji)的(de)生成,進(jin)而導致DNA損傷,產生更為(wei)嚴(yan)重的(de)損害。有調(diao)查表明,不接(jie)(jie)觸(chu)(chu)溫(wen)(wen)石(shi)(shi)棉(mian)(mian)(mian)的(de)吸煙(yan)(yan)者(zhe)肺(fei)癌相對(dui)危險度(RR)為(wei)26,不吸煙(yan)(yan)的(de)溫(wen)(wen)石(shi)(shi)棉(mian)(mian)(mian)接(jie)(jie)觸(chu)(chu)者(zhe)肺(fei)癌RR為(wei)12.2,而接(jie)(jie)觸(chu)(chu)溫(wen)(wen)石(shi)(shi)棉(mian)(mian)(mian)的(de)吸煙(yan)(yan)者(zhe)肺(fei)癌RR高達32.1,吸煙(yan)(yan)和(he)(he)溫(wen)(wen)石(shi)(shi)棉(mian)(mian)(mian)接(jie)(jie)觸(chu)(chu)協(xie)同(tong)指(zhi)數(shu)為(wei)2.2。
降低溫石棉致(zhi)病性的研究
有研究發現(xian)(xian)經檸檬酸鋁、混合(he)稀土或亞硒酸鈉(na)3種化合(he)物(wu)預處理(li)的(de)(de)溫(wen)石(shi)棉纖維表面元素的(de)(de)構成和含量均發生(sheng)變化,導致相比(bi)未預處理(li)的(de)(de)溫(wen)石(shi)棉,該(gai)類(lei)溫(wen)石(shi)棉作用(yong)于細(xi)胞(bao)時,細(xi)胞(bao)的(de)(de)酸性(xing)磷酸酶活性(xing)降低,人胚肺細(xi)胞(bao)存活率提高及(ji)超微結構改(gai)變,癌(ai)基(ji)因轉錄水平降低,最(zui)終減輕了(le)溫(wen)石(shi)棉的(de)(de)細(xi)胞(bao)毒性(xing)。另有研究發現(xian)(xian)大蒜提取物(wu)能有效減少溫(wen)石(shi)棉對外周血(xue)淋巴細(xi)胞(bao)的(de)(de)基(ji)因毒性(xing)。
溫(wen)石(shi)棉所致職業性腫瘤流行病學研究
國內(nei)大量流行病(bing)學調查研(yan)究提示溫石棉粉塵在接(jie)觸(chu)濃度超標條件下(xia)具(ju)有(you)顯著的(de)致病(bing)性(xing)。
對重(zhong)慶石(shi)(shi)(shi)棉廠(chang)(chang)接觸(chu)純(chun)溫石(shi)(shi)(shi)棉工(gong)人(ren)的(de)25年(nian)縱(zong)向隊列(lie)研究(jiu)(jiu)顯(xian)示(shi),生料間(jian)和紡織間(jian)的(de)粉塵(chen)濃(nong)度(du)分別為7.6f/mL和4.5f/mL,接塵(chen)組的(de)肺癌發病率(lv)是不接塵(chen)組的(de)8.1倍。對中國另一大型(xing)石(shi)(shi)(shi)棉廠(chang)(chang)515名單純(chun)接觸(chu)溫石(shi)(shi)(shi)棉的(de)工(gong)人(ren)進行27年(nian)的(de)追蹤研究(jiu)(jiu)發現,其20世紀60年(nian)代(dai)前溫石(shi)(shi)(shi)棉粉塵(chen)平均(jun)濃(nong)度(du)為146.2mg/m3,20世紀90年(nian)代(dai)后降低到(dao)10mg/m3,單純(chun)接觸(chu)溫石(shi)(shi)(shi)棉工(gong)人(ren)的(de)肺癌發生率(lv)顯(xian)著超高(P<0.05)。
另有(you)長達41年調查(cha)浙江家庭溫(wen)石(shi)(shi)棉(mian)(mian)(mian)手工(gong)紡織業的(de)研究發現,其(qi)20世(shi)紀60年代作(zuo)業環境(jing)的(de)溫(wen)石(shi)(shi)棉(mian)(mian)(mian)粉塵濃度38.00~73.00mg/m3,20世(shi)紀70年代降低到平均為(wei)1.25 mg/m3,但仍超(chao)標,作(zuo)業女工(gong)5681人中(zhong)累(lei)計死(si)亡858例(li),其(qi)中(zhong)213人死(si)于癌(ai)癥,肺(fei)(fei)癌(ai)居首位(87例(li),占(zhan)40.85%),肺(fei)(fei)癌(ai)標準(zhun)化死(si)亡比3.88,明(ming)顯高于當地女性年齡別標準(zhun)化死(si)亡比。對(dui)某大型溫(wen)石(shi)(shi)棉(mian)(mian)(mian)礦研究發現,接觸(chu)溫(wen)石(shi)(shi)棉(mian)(mian)(mian)可(ke)以(yi)提高礦工(gong)肺(fei)(fei)癌(ai)、石(shi)(shi)棉(mian)(mian)(mian)肺(fei)(fei)等疾病的(de)死(si)亡率。而國外研究認為(wei),低于限值濃度的(de)溫(wen)石(shi)(shi)棉(mian)(mian)(mian)纖維粉塵不會造成健(jian)康風(feng)險。毒(du)理學博(bo)士(shi)David Bernstein的(de)研究表(biao)明(ming),溫(wen)石(shi)(shi)棉(mian)(mian)(mian)和(he)角(jiao)閃石(shi)(shi)在動力和(he)病理上都存在差異,其(qi)他類似(si)研究也展示出對(dui)溫(wen)石(shi)(shi)棉(mian)(mian)(mian)的(de)低程度接觸(chu)不會導致可(ke)被檢測的(de)安全風(feng)險。
有證(zheng)據表(biao)明,高(gao)濃(nong)度和長時間(jian)(jian)接(jie)(jie)觸(chu)溫(wen)石(shi)棉可(ke)(ke)以產(chan)生(sheng)肺(fei)癌(ai),低(di)濃(nong)度溫(wen)石(shi)棉不(bu)存在可(ke)(ke)檢測的(de)(de)健康風險,即使短時間(jian)(jian)接(jie)(jie)觸(chu)高(gao)濃(nong)度溫(wen)石(shi)棉,發(fa)生(sheng)健康風險的(de)(de)概率也不(bu)高(gao)。希臘持續(xu)39年的(de)(de)關(guan)于接(jie)(jie)觸(chu)純溫(wen)石(shi)棉的(de)(de)水泥工人的(de)(de)研究表(biao)明,對(dui)純凈(jing)溫(wen)石(shi)棉在允許范圍內的(de)(de)職(zhi)業接(jie)(jie)觸(chu)與肺(fei)癌(ai)以及(ji)間(jian)(jian)皮瘤的(de)(de)顯著增(zeng)長無關(guan)。而有巴西的(de)(de)研究發(fa)現(xian),減(jian)少石(shi)棉接(jie)(jie) 觸(chu)可(ke)(ke)以顯著降(jiang)低(di)石(shi)棉肺(fei)、實質和/或良性胸膜疾病的(de)(de)發(fa)病率。
溫石(shi)棉(mian)同角(jiao)閃石(shi)類石(shi)棉(mian)致病(bing)性差異的流行病(bing)
溫(wen)石(shi)(shi)棉(mian)和角閃(shan)石(shi)(shi)石(shi)(shi)棉(mian)在吸入(ru)毒性(xing)和致病性(xing)上存在差異。David Bernstein認為,在化學特(te)性(xing)和礦(kuang)物學特(te)性(xing)方面,溫(wen)石(shi)(shi)棉(mian)與(yu)其他角閃(shan)石(shi)(shi)石(shi)(shi)棉(mian)差異明(ming)顯(xian),可(ke)以(yi)從肺中更快(kuai)速(su)地被清除(chu)。
6個中歐、東(dong)歐國(guo)家和英(ying)國(guo)的(de)(de)(de)多中心(xin)對(dui)照研究發(fa)現,職(zhi)業接觸石(shi)(shi)棉(mian)似乎并(bing)不促進男性肺(fei)癌(ai)的(de)(de)(de)發(fa)病,溫(wen)石(shi)(shi)棉(mian)誘(you)發(fa)肺(fei)癌(ai)的(de)(de)(de)概(gai)率小(xiao)于溫(wen)石(shi)(shi)棉(mian)合(he)并(bing)角閃石(shi)(shi)石(shi)(shi)棉(mian)。另有(you)研究計(ji)數133名間(jian)(jian)皮瘤(liu)患(huan)者和262名肺(fei)癌(ai)患(huan)者的(de)(de)(de)肺(fei)組織標本中長度超過5μm的(de)(de)(de)石(shi)(shi)棉(mian)纖(xian)維數目,發(fa)現溫(wen)石(shi)(shi)棉(mian)纖(xian)維僅(jin)占2%。英(ying)國(guo)健康安全理(li)事會的(de)(de)(de)研究表明溫(wen)石(shi)(shi)棉(mian)和其(qi)他兩類角閃石(shi)(shi)石(shi)(shi)棉(mian)在(zai)間(jian)(jian)皮瘤(liu)風險上的(de)(de)(de)差異為1∶100∶500。總(zong)結71個石(shi)(shi)棉(mian)群體的(de)(de)(de)廣泛(fan)的(de)(de)(de)流行病學研究表明,沒有(you)任何(he)證(zheng)據支持未被角閃石(shi)(shi)污(wu)染的(de)(de)(de)溫(wen)石(shi)(shi)棉(mian)會導致間(jian)(jian)皮瘤(liu)的(de)(de)(de)這(zhe)種假設。
溫(wen)石棉致病機制的研究方向及展望
溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)致(zhi)(zhi)癌和(he)致(zhi)(zhi)纖維化(hua)的機(ji)制(zhi)十分復雜(za),至今仍存(cun)在(zai)(zai)(zai)很多尚未研究清楚之(zhi)處。比如(ru)溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)在(zai)(zai)(zai)細胞(bao)(bao)信號(hao)傳導層面(mian)的完整致(zhi)(zhi)病(bing)機(ji)制(zhi)如(ru)何;不同產(chan)地的溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)成分有所(suo)不同,對溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)的致(zhi)(zhi)病(bing)性(xing)影響如(ru)何;溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)同時具(ju)有致(zhi)(zhi)癌性(xing)和(he)致(zhi)(zhi)纖維化(hua)性(xing),溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)有哪(na)些(xie)較其他(ta)致(zhi)(zhi)癌物(wu)或致(zhi)(zhi)纖維化(hua)物(wu)質不同之(zhi)處;在(zai)(zai)(zai)細胞(bao)(bao)層面(mian),溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)和(he)其他(ta)種(zhong)類石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)的致(zhi)(zhi)病(bing)機(ji)制(zhi)存(cun)在(zai)(zai)(zai)哪(na)些(xie)區(qu)別;是否存(cun)在(zai)(zai)(zai)有效降(jiang)低溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)致(zhi)(zhi)病(bing)性(xing)的方(fang)法(fa)及其應(ying)用等。對溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)致(zhi)(zhi)病(bing)機(ji)制(zhi)、影響因素及降(jiang)低毒(du)性(xing)方(fang)法(fa)的完整研究,可以幫助人們更(geng)全(quan)面(mian)地認識溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)的危害,并在(zai)(zai)(zai)此基礎上(shang)研發(fa)適宜的防護(hu)措施和(he)防護(hu)手段,以更(geng)安全(quan)、健康地應(ying)用溫(wen)石(shi)(shi)(shi)(shi)棉(mian)(mian)(mian)。