Determination of local adherence factor of soil to skin and assessment of health risk for children around a soil contaminated site

透過土壤攝入及皮膚接觸兩種暴露途徑，土壤及灰塵中的污染物容易進入人體並造成健康危害。而六歲以下孩童容易將手放進嘴巴的行為使孩童的暴露風險高過成人。在皮膚接觸的暴露途徑中，土壤黏附因子是評估暴露風險的重要因子之一，部分研究更指出污染物容易黏附在細小的土壤顆粒中。然而，因為台灣六歲以下孩童的土壤黏附因子尚未被完整建立，目前台灣主要仍使用美國環保署提供的參數做健康風險評估，使用非本土性的參數可能會使健康風險評估的結果被高估或低估。 因此，本研究透過田野調查，以顆粒細小的黏土性質建立台灣六歲以下孩童的土壤黏附因子，另外透過砂土和黏土的不同土壤性質實驗、探究影響土壤黏附的因素，以及土壤黏附至皮膚、轉移至口中的粒徑變化。並以關渡平原的土壤與地下水污染場址為例，利用建立之土壤黏附參數推估六歲以下孩童經由土壤介質造成的暴露劑量及致癌風險。本研究結果指出，包括活動型態、衣著、土壤類型、土壤含水率和接觸壓力等，皆會影響土壤的黏附量。而暴露越大範圍的身體表面積及在地面上高強度的活動型態會使孩童有較高的暴露風險。在土壤粒徑的轉移結果，不論砂土或黏土，從土壤轉移至皮膚、及透過舔允行為轉移至口中的粒徑皆小於150μm。 透過本研究結果，所建立之台灣六歲以下孩童的黏附因子不僅可作為台灣未來健康風險評估的參數參考依據，也可以提供政府管理單位針對台灣的孩童風險做適當的管理及決策。Contaminants in soil and dust may cause adverse health effects on human through soil ingestion and dermal contact exposure routes. Hand-to-mouthing behaviors could lead children under six years old to greater health risk than adults. For the dermal contact of the exposure route, the soil adherence factor is a major parameter influencing the exposure risk assessment. Some studies also showed that contaminant is easy to adsorb in soil with small particle size. However, researches pertaining to establishing the local data of soil adherence factor for children under six years old in Taiwan were still missing. Using the published soil adherence data from U.S.EPA may over- or under-estimate the risk result of children in Taiwan. This study attempts to establish the local adherence factor for children under six years old in Taiwan. The tested soil with a clay texture was obtained from field sampling, and the potentially influencing factors of dermal contact on soil adherence were evaluated. The tendency of particle size variation by transferring from soil to hand and hand to mouth was also investigated by hand-press trial experiments. Moreover, the obtained adherence factor was used assess the children health risk in Guandu Plain, a contaminated site in Northern Taiwan. The experimental results revealed that several factors substantially influencing the adherence factor, including activity, clothing, soil moisture content, and contact pressure. Larger exposure area of body surface and high intensity of activity led children to higher exposure risk. The sizes of particles transferred from soil to hand and hand to mouth are mainly less than 150 μm. Results of the study can not only be regarded as a reference to the children health risk assessment of contaminated sites, but also provide the suggestions on strategy and measurement in the risk management