有機溶劑中毒預防規則中的暴露評估模式應用

Application of Exposure Assessment Model in Regulation to Prevent from the Intoxication of Organic Solvent

有機溶劑中毒預防規則是我國重要的作業場所化學物質危害防制法令。此法令原本是參考日本法令所制定。根據回溯探討，可以發現規則中有關有機溶劑分類、容許消費量與通風換氣要求等量化規定早期係依據飽和蒸氣壓模式、無通風模式與暴露空間模式等量化暴露評估模式所建立。上述模式目前均為美國工業衛生協會所接受的初步暴露評估方法。無論採用何種模式，都需要事先訂定各種化學物質的容許濃度或暴露上限。根據飽和蒸氣壓模式，有機溶劑飽和蒸氣壓對濃度上限的比值可用以初步決定所需採用的控制設施。而在有機溶劑中毒預防規則中，需要使用密閉或局部排氣裝置的第一種有機溶劑，上述比值大略在1,000以上。無通風模式則是推估以室內既有空氣量稀釋有機溶劑消費量所可達到的濃度，進而可用以決定有機溶劑容許消費量。暴露空間模式則是推估在穩定有機溶劑釋放率與通風換氣率所能達到穩定濃度，也可用以推估在給定有機溶劑消費率下將空氣中有機溶劑濃度維持於容許值所需的通風換氣率。有機溶劑中毒預防規則中，第一、二種有機溶劑的容許消費量與通風換氣能力需求均接近依各種有機溶劑計算所得的中位數。面對更多形式的化學暴露，我國目前已制定涵蓋範圍更廣的危害性化學品評估及分級管理辦法，此法令也接受將量化模式做為職業場所暴露評估方法。本研究對有機溶劑中毒預防規則與量化暴露評估模式的比對與回溯，將有助於事業單位在新法令規範下依相同評估程序，自行建立對各種化學物質的規範與控制措施。

Regulations to Prevent Toxication by Organic Solvent is one of the important decrees that control the chemical hazards in occupational site. It was originally adapted from Japan. In this regulation, the provisions related to the categorization of organic solvents, the tolerant consumption amount, and the requirement of displaced ventilation were found to be based on saturation vapor pressure model, zero ventilation model, and box model. These quantitative exposure assessment models have been accepted by AIHA as primary methods to evaluate the occupational exposure hazard. No matter which model to be used, a permitted exposure level for each concerned organic solvent must be determined at first. According to saturation vapor pressure model, the control facilities can be determined by the ratio of saturation vapor pressure of a concerned organic solvent to its permitted exposure level. In Regulations to Prevent Toxication by Organic Solvent, the first kind organic solvents are required to be controlled by a closure or local exhaust system. The above ratio of this kind of organic solvents was found to be above 1000. Zero ventilation model estimates the concentration of a chemical diluted by the existing air in a room. This model can determine the permitted consumption amount of an organic solvent. Box model estimates the steady-state concentration of an organic solvent under a given consumption and ventilation rates. In above Regulation, the permitted consumption amount and required ventilation of the first and second kind organic solvents are close to the median values calculated from those of each kind. To deal with a variety of chemicals, a domestic Stipulation on Hazardous Chemicals Assessment and Categorization Management was drawn up. This stipulate regards the quantitative models as the acceptable methods to assess the exposure in occupational sites. This study compared and retrospected above Regulations and related quantitative exposure assessment models. The results are helpful for an employer to establish his own measure to control a variety of chemicals by following a similar logic presented in this study under the Stipulation.