多氯戴奧辛、多氯夫喃、與多氯聯苯可持久性存在環境中，人類的主要暴露途徑為呼吸、飲食、接觸等。戴奧辛可影響實驗動物的生殖發育，流行病學研究指出戴奧辛會引起人類的癌症與多種不良健康效應，國際組織針對戴奧辛訂定可容許攝取量或癌症斜率因子，有許多研究探討各國人群的暴露風險，然而國人的戴奧辛暴露與其健康風險尚未被充分了解，本計畫之目的為評估各群組國人之每日戴奧辛總暴露量並描述其健康風險。本研究依循風險評估基本架構：危害鑑定、劑量反應評估、暴露評估、及風險特徵描述進行，探討17種多氯戴奧辛╱夫喃與12種有類戴奧辛作用的多氯聯苯(簡稱戴奧辛)，以世界衛生組織的toxic equivalency factors計算毒性當量。在暴露評估步驟，結合國內空氣、食物、與土壤之戴奧辛濃度資料以及國人的飲食攝取量、飲水量、呼吸速率、及土壤攝取量，估計各群組國人之戴奧辛暴露量，進而計算各群組國人戴奧辛暴露佔Joint FAO╱WHO Expert Committee on Food Additives (JECFA)的provisional tolerable monthly intake (PTMI)之百分比，並且以US EPA的斜率因子試算癌症風險。本研究採用simple distribution與Monte Carlo simulation兩種方法估計暴露量與風險。研究結果顯示：在所有性別-年齡組別的一般民眾或焚化廠附近居民，其平均總戴奧辛暴露皆低於28 pg WHO-TEQ╱kg bw╱month，佔PTMI的40%以下；在一般民眾，93%-98% 的戴奧辛暴露來自飲食；而焚化廠附近居民，其86%-95% 的戴奧辛暴露來自飲食，4.5% - 14%來自空氣。以simple distribution與Monte Carlo simulation兩種方法所得結果相近。當以US EPA的斜率因子估算癌症風險時，所有性別-年齡組別的致癌風險皆超過1×10-5，與以JECFA的方法估計之風險差異很大。本研究以JECFA方法所得的結果顯示台灣民眾的戴奧辛暴露在可容許範圍，且無明顯的致癌與非致癌風險。然而，有2.5%的民眾、或是6.5%的小於13歲者其戴奧辛暴露超過PTMI，應設法降低其飲食戴奧辛暴露量。再者，本研究受限於其他各類食物的戴奧辛濃度資料不足，可能低估民眾的總戴奧辛暴露量。 Polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are ubiquitous and persistent in the environment. Previous studies suggested that long-term exposure to dioxins increased the risk of cancer and various adverse health effects in human. The purposes of this study were to estimate daily intake of dioxins and to assess the health risk from dioxins for the populations in Taiwan. This study evaluated the effects of 17 PCDDs╱PCDFs congeners and 12 coplanar PCBs and used the term dioxins to represent them. Exposure assessment includes estimation of daily intake of dioxins from inhalation, ingestion of food and water, and soils for the general population and residents near waste incinerators. The estimated daily intake was compared with the provisional tolerable monthly intake (PTMI) established by the Joint FAO╱WHO Expert Committee on Food Additives (JECFA). The US EPA cancer slope factor was used to estimate the upper-bound cancer risk. Simple distribution and Monte Carlo simulation methods were applied to estimate exposures and risk. The results showed that for 14 age-sex group in the general population or in residents near waste incinerator, means of total intake for dioxins were less than 28 pg WHO-TEQ╱kg bw╱month. The mean %PTMI values were under 40%. In the general population, 93%-98% of the daily dioxin exposure was contributed to diet. Among residents near waste incinerators, 86%-95% of their dioxin exposure was contributed to diet and 4.5%-14% to inhalation. Results of the Monte Carlo simulation showed that the mean %PTMI ranged from 25% to 36 % for 10 age-sex groups in the general populations. The estimated cancer risk, using the US EPA slope factor, was greater than 1*10╱sup -5╱ in all age-sex groups, which was contradictory to risk estimated by the JECFA approach. The study results imply that means of exposures to dioxins for the general population are well within the tolerable intake and there is no appreciable risk for both cancer and non-cancer effects when JECFA approach was used. However, 6.5% of subjects aged younger than 13 years had exposure greater than PTMI. Measures should be taken to reduce exposures in these subjects. Furthermore, this study could underestimate the exposures due to lack of dioxin concentration data for all food groups.
