A Study of the Mass Balance of Dioxins and Furans in Lactating Cows in Background Conditions
Consumption of animal fats account for as much as 95% of the human background exposure to compounds with dioxin-like activity. Although it is generally believed that most domestic meat and dairy animals receive most of their exposure from their feed, there is limited data available on levels of dioxin-like compounds in animal feeds. The purpose of this study was to first confirm that feed is the primary source of dioxin exposure for the dairy cattle under study. This was to be accomplished by conducting a mass balance study. A second objective was to use the mass balance data to derive steady-state bioconcentration factors (BCFs, BTFs, and CRs). Future studies will use these bioconcentration factors to look at feed and milk concentration in a number of dairy operations to determine if feed accounts for most of the exposure to dairy animals. This study is described in two parts. This paper presents the data on levels of dioxin in the feed and makes some conclusions about its variability, and the contribution to overall feed concentration made by the various feed components. The second paper summarizes the mass balance results and generates bioconcentration parameters (BCF, BTF, and CR) for the dioxin and furan (CDD/F) congeners. This study did not investigate the dioxin-like coplanar PCBs.