Bioconcentration of Dioxins and Furans in Vegetation

Information sources for bioconcentration factors (BCFs) from the existing technical literature include models based on K _ow and/or regulatory agency guidance from agencies such as USEPA. Since magnitude assignments of BCFs influence the degree of conservativeness implicit in risk assessments, the BCF magnitudes for a contaminated site in Ontario, Canada, were assessed from field measurements for dioxins and furans from soil to vegetation and are compared with BCFs from the literature. It is demonstrated that observed BCFs for dioxins and furans from the field study are generally much higher (3 to 575 times for 15 compounds and 2,770 times for Octa CDF) than those computed by the USEPA method and are higher by a factor of 3 to 650 (for eight compounds) computed by the K _ow model. These findings indicate that use of model-based BCFs may result in underestimation of the risk or hazard.