一般在自然界中暴露到鉻的來源除了包括職業場所的工作暴露（空氣暴露、皮膚暴露）外，飲食中的蔬菜、肉類也會有微量鉻的存在，因此鉻也會經由口服的途徑進入到體內。而目前尿中的總鉻濃度往往被當作是鉻的生物暴露指標。文獻中大多假設尿中鉻是以三價型式存在，對於尿中是否有Cr(VI)的存在則尚未有實際量測資料，此外、過去對於鉻暴露之尿中鉻動力學探討有限。因此本研究利用職業暴露與動物實驗探討不同價數鉻(VI/III)暴露下，尿中鉻濃度之分布與動力學資料，因此，本研究目的為:(1)利用離子色層分析儀(IC)來測試高鉻暴露之實驗動物與職業鉻暴露員工之尿中六價鉻的存在與否(2)探討兩種鉻暴露職業(色料及皮革廠)下生物偵測研究及尿中六價鉻是否存在 (3)利用口服途徑的動物實驗方式，來建立不同價數鉻暴露下鼠尿中總鉻的動力學模式，以了解鉻在體內的分佈情形(4)利用皮膚暴露途徑的動物實驗方式，來比較在不同價數鉻暴露下，剃毛與否對皮膚吸收的影響及鼠尿中總鉻的變化情形。
本研究採集了兩種職業(色料及皮革廠)鉻暴露工廠之勞工的空氣、皮膚以及尿液樣本來作為一般職場的監測。另外再利用動物實驗的方式，在兩種價數(Cr(III)及Cr(VI))鉻暴露的情形下，給予口服與皮膚兩種不同途徑的暴露，並以Inductively Coupled Plasma-Mass Spectrometer(ICP-MS)和Ion Chromatography(IC)來進行尿液樣本的分析。結果顯示，兩家工廠空氣中的幾何平均濃度明顯低於法定的容許濃度值(PEL=100μg/m3)，而皮膚樣本的幾何平均濃度範圍分別為0.12~0.32μg/cm2(色料廠中)及0.04~0.16μg/cm2(皮革廠中)。經統計分析後發現，皮膚暴露方面以手部的暴露濃度顯著高於身體其他部位(P<0.05)。在尿液總鉻濃度中則發現色料廠皆低於偵測下限(即<0.126μg/L)而皮革廠員工之幾何平均上班前、下班前之濃度分別為6.71  1.78μg/g creatinine及13.84  1.57μg/g creatinine皆低於ACGIH之BEI值(工作前後尿中總鉻的差異量為10 μg/g creatinine)。另外，利用IC來進行尿液分析後發現，在此種暴露情形下，尿中並無可測得之六價鉻。在Wistar rat之實驗中，分別進行皮膚浸泡100 mg/L （分成剃毛及未剃毛兩種）35分鐘及灌食3 mg(口服)方式，給予Cr(VI)、Cr(III)單獨和兩者混合之暴露，結果發現口服Cr(VI)與Cr(III)+Cr(VI)，尿中總鉻之排除曲線符合First-order kinetics。並且發現共同Cr(III)+Cr(VI) 暴露與Cr(VI)單獨暴露相較時，在實驗動物體內之尿中總鉻排除曲線之半衰期、AUC與Cl等動力學參數值，前者皆較後者為高，故推論一般人在六價鉻的職業暴露下，同時有其他諸如口服之三價鉻暴露，可能會增加鉻暴露的危險性。而在濃度100 mg/L的皮膚暴露途徑下亦發現，同時暴露到Cr(VI)+Cr(III)時，尿中的總鉻平均濃度明顯的高於未進行實驗前的尿中總鉻濃度，故可推知共同暴露到Cr(VI)+Cr(III)時，可能較個別暴露易於經由皮膚吸收而進入到體內。此外，利用IC來針對高劑量的口服實驗下之尿液測試，結果發現尿中無法測得六價鉻，此與過去文獻的發現一致。

Two main routes of exposure to chromium for humans are from occupation and from diet. Currently, total chromium concentration in urine has been used as the biomarker of chromium exposure. Chromium III was assumed the only form existing in urine. Chromium VI, however, has not been conclusively excluded from its existence in urine. Moreover, very limited studies have been conducted in excretory chromium kinetics. The objectives of this study were : 1. to verify whether there is chromium VI in urine by using ion chromatography (IC), a more sensitive analytical tool; 2. to explore the biological monitoring of occupational exposure to chromium in pigment and leather industries; 3. to establish the kinetics of excretory chromium after oral administration in animal experiments; 4. to compare the dermal absorption between intact skin and stripped skin on the total urinary chromium.
This study was completed by two approaches. First of all, the exposure assessment of air and skin as well as biological monitoring were performed in the workers from pigment and leather industries. Secondly, Wistar rats were exposed to two valance-specific forms of chromium by both oral and dermal routes. The urinary chromium concentrations collected before and after the exposure, along with the airborne and dermal monitoring samples, were determined by Inductively coupled plasma-mass spectrometer (ICP-MS) and IC, respectively. We found the airborne exposure concentrations of chromium in two chromium-exposed manufacturing workers were far below current exposure limit (PEL=100 μg/m3) and the geometric mean of skin exposure concentrations of chromium were 0.12~0.32μg/cm2 (in pigment) and 0.04~0.16μg/cm2 (in leather), respectively. Skin exposure on hands, however, showed significantly higher than that on the rest of other body sites. The total chromium concentration of urine were all below detection limit (<0.126μg/L) in pigment. The urinary chromium concentrations were 6.71  1.78μg/g creatinine and 13.84  1.57μg/g creatinine among pre-shift and post-shift for leather manufacturing workers although all of them were far below the current BEI setting of chromium exposure (= 10 μg/g creatinine). None of any detectable chromium VI forms were found by IC.
In animal experiments, Wistar rats were exposed to chromium III and chromium VI at the dose of 3mg separately and together by oral route, respectively. For dermal exposure, Wistar rats with intact skin and with stripped skin were exposed to chromium III and chromium VI at 100 mg/L separately and together at 100 mg/L, respectively. We found, in oral exposure experiments, the excretory total chromium in urine followed the first-order kinetics curve for the groups of chromium VI and chromium VI+III. The half-life, area under curve (AUC) and clearance (Cl) in urine were higher when simultaneous exposure to chromium VI and chromium III. It suggests that people simultaneously exposed to chromium VI and chromium III might have higher risk of chromium-related diseases.
In skin exposure experiment, we found urinary chromium concentrations in post-exposure overtly higher than that in pre-exposure when Wistar rats were exposed to chromium VI and chromium III at 100 mg/L simultaneously. Moreover, none of any chromium VI could be detected in the urine samples collected from oral exposure at the experimentally highest dose of chromium, indicating the findings of no existing chromium III could not be rejected.

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