為了能夠適切呈現勞工作業場所相似暴露群(similar exposure group, SEG)的暴露實態，必須採集多次且長期的樣本，惟受限於成本與人力，僅有少數事業單位能夠負擔這樣的支出。因此本研究的目的在於應用貝氏決策分析技術(Bayesian decision analysis , BDA)，發展整合式方法，針對螺絲製造工廠勞工使用切削油產生之油霧滴(oil mist)與多環芳香烴化合物(polycyclic aromatic hydrocarbons, PAHs)，進行暴露與健康風險評估。本研究包括三個部分，第一部分的研究為在一年中隨機量測十一次油霧滴濃度(Cm, n = 11)，作為貝氏決策分析之可能性分布(likelihood distribution)，每日螺絲生產量(Production rates, Pr, n=250)則作為螺絲製造工廠搓牙勞工之長期油霧滴暴露替代指標(Cp)，同時也是貝氏決策分析之事前分布(prior distribution)。油霧滴長期暴露結果則藉由貝氏決策分析之事後分布(posterior distribution)加以評估，此外本研究所提方法之有效性則以改變油霧滴濃度樣本數之多寡加以驗證。第二部分的研究則延續第一部分研究所發展之以螺絲生產量預測油霧滴濃度模式，加上以累積螺絲生產量(Cumulative production rate, CPr)預測切削油內多環芳香烴化合物含量模式，藉由應用年度螺絲生產量及累積生產量記錄於上述兩個模式，可加以預測工作場所內長期吸入性多環芳香烴化合物之暴露濃度，預測濃度及實測濃度分別作為貝氏決策分析之事前分布與可能性分布，事後分布結果則作為勞工長期暴露與健康風險評估之依據。第三部分的研究亦是利用整合式方法針對多環芳香烴化合物在皮膚上的暴露進行健康風險評估，先以油霧滴濃度作為替代指標，建立皮膚暴露濃度預測模式，再以預測濃度作為貝氏決策分析之事前分布，實測濃度作為可能性分布，最終則以事後分布作為多環芳香烴化合物對於皮膚之健康風險評估。第一部份的研究結果發現：搓牙作業勞工之油霧滴暴露在胸腔區（thoracic）及可呼吸區（respirable）區域比在可吸入性（inhalable）區域較為嚴重，利用螺絲生產量（Production rate, Pr）作為油霧滴濃度（Cm）的替代指標是適當的（~92% variations of Cm）。研究結果顯示貝氏決策分析技術結合了預測油霧滴濃度（Cp）及實測油霧滴濃度（Cm），對於預測長期勞工暴露是有效益的，此外，藉由檢驗事後暴露等級之一致性，研究結果顯示在實測油霧滴濃度樣本數低至三時，本方法仍可適用。第二部份的研究結果發現：螺絲累積生產量則可用以預測金屬加工用油中內PAHs含量，結合預測之油霧滴濃度及預測之金屬加工用油中PAHs含量，利用貝氏決策分析技術可有效推估出作業環境空氣中PAHs濃度，PAHs長期暴露經評估有3.1%機率會超過OEL-TWA (0.2 mg/m3)，有96.7%機率會超過action level (0.1 mg/m3)，更有73.4%機率會超過50倍可接受健康風險（10-3），此一結果顯示應立即採取預防性的措施，以降低勞工在呼吸性PAHs之暴露。第三部分研究結果發現：可利用空氣中油霧滴濃度作為預測皮膚PAHs暴露濃度之替代指標，相較於第二部分勞工暴露可吸入性氣相Total-PAHs有73.4%機率會超過50倍可接受健康風險（10-3），勞工之皮膚暴露於Total-PAHs也有32.6%機率會超過37.5倍可接受健康風險（10-3）。研究發現利用貝氏決策分析技術推估之致皮膚癌超過可接受健康風險之機率低於終生致肺癌超過可接受健康風險之機率，然而兩者均高於美國最高法院定義之顯著危害風險值(10-3)，因此本研究建議應優先針對搓牙機械等設備設置有效之局部排氣裝置，並要求作業勞工配戴適當呼吸防護具並減少皮膚暴露於作業環境中之時間。

Collecting multiple and long-term samples is necessary for properly describing the exposure profile of a similar exposure group (SEG), but only few industries are affordable because of the cost and manpower. An integrated approach was developed in this study to assess workers’ exposures to oil mist, and polycyclic aromatic hydrocarbons (PAHs) (including inhalatory and dermal) arising from processes using metalworking fluids (MWFs) in a fastening industry. This study includes three parts. In the first study, measured oil mist concentrations (Cm, n = 11) were randomly collected on eleven days during one year (served as the likelihood distribution in Bayesian decision analysis (BDA), and daily fastener production rates (Pr, n = 250) were used as a surrogate for predicting the yearlong oil mist exposure concentrations (Cp) (served as the prior distribution in BDA). The resultant BDA posterior distributions were used for assessing the long-term oil mist exposures to threading workers in a fastener manufacturing industry. The feasibility of the proposed methodology was finally examined by reference to the effect caused by the sample size of the Cm. In the second study, one previously developed model in first study and one new model were adopted for predicting oil mist exposure concentrations emitted from MWFs and PAHs contained in MWFs by using the fastener Pr and cumulative fastener production rate (CPr) as predictors, respectively. By applying the annual Pr and CPr records to the above two models, long-term workplace inhalatory PAH exposure concentrations were predicted. In addition, true exposure data was also collected from the field. The predicted and measured concentrations respectively served as the prior and likelihood distributions in the BDA, and the resultant posterior distributions were used to determine the long-term exposure and health-risks posed on workers. The third part study was to develop an integrated approach for conducting long-term health-risk assessments on dermal PAHs for fastener manufacturing industry workers. The approach involves first the development of a predictive model, based on the surrogate method, for predicting long-term oil mist and dermal PAHs concentrations in the workplace. Then, the predicted long-term oil mist and dermal PAHs concentrations and limited field measured dermal PAHs concentrations were served as the prior and likelihood distribution in the BDA, respectively. Finally, the resultant posterior distributions were used to assess the long-term dermal PAHs health-risk posed on fastener manufacturing industry workers. The results obtained from the first study show that threading workers experienced more severe thoracic and respirable oil mist exposures than the exposures to the inhalable fraction. Using Pr as a surrogate was adequate to explain ~92% variations of Cm. By combining Cp and Cm, our results suggest that the adopted BDA technique was beneficial for predicting workers’ long-term exposures. By judging the consistency of the resultant posterior exposure ratings, this study suggests that the proposed methodology could be feasible even the sample size of Cm was set as low as 3. The results obtained from the second part show that long-term exposures to inhalatory PAHs would result in a 3.1%, 96.7%, and 73.4% chance of exceeding the OEL-TWA (0.2 mg/m3), action level (0.1 mg/m3), and 50 times of acceptable health risk (10−3), respectively. The result from the third part show that the dermal PAH exposure levels was 5.88×106 ng/day and the top five exposed surface areas were lower arm, hand, upper arm, neck, and head/front. The estimated probability of excess lifetime skin cancer risk was lower than that of lung cancer risk, but both were higher than the significant risk level (10-3) defined by the US Supreme Court in 1980. The installation of a local exhaust ventilation system at the threading machine should be considered as the first priority measurement because both lung and skin cancer risks can be reduced simultaneously. If the personal protection equipment would be adopted in the future, both respiratory protection equipment and protective clothing should be used simultaneously.

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