Analysis of Animal-and Plant-Derived Feed Ingredients for Dioxin-Like Compounds
During a national survey of polychlorinated dibenzo-p-dioxins (CDD), dibenzofurans (CDF), and dioxin-like coplanar PCBs (PCB) in poultry, elevated concentrations above 20 parts per trillion (ppt) toxic equivalents (TEQ) were found in the fat of 2 broilers. These TEQ values were driven by very high concentrations of CDD. A team comprised of individuals from the United States (US) Environmental Protection Agency (EPA), the US Food and Drug Administration (FDA), and the US Department of Agriculture (DA) traced the source of elevated CDD to a minor component in the poultry feed. This component was ball clay and it was used as an anti-caking agent in the soybean meal. The ball clay often comprised less than 0.2% of the dry weight of the complete ration in contaminated poultry. The investigation traced the ball clay to a mine in Mississippi. After learning that other ball clay mines in Kentucky and Tennessee also contained elevated CDD levels, the FDA issued a letter to producers or users of clay products in animal feeds asking that they cease using ball clay in any animal feed or feed ingredient. Subsequent contaminations of animal feed in Belgium with PCB and of citrus pulp from Brazil with CDD and CDF alerted countries worldwide that animal feeds can become contaminated with CDD/CDF/PCB (DFP) via contamination of minor feed components. This type of contamination can overshadow the normal air-to-leaf process that is thought to dominate the food chain for terrestrial food animals in background conditions. Following the ball clay incident, the US EPA, FDA and DA have coordinated their efforts to monitor for DFP in animal- and plant-derived food products, complete animal feeds, and animal feed ingredients. This has been done in order to better understand the background DFP status of the food supply and how that food supply comes to attain levels of DFP. In 1998, the Center for Veterinary Medicine (CVM) of FDA collected several anti-caking products used in animal feeds and oilseed meals. The samples from this survey were analyzed by the EPA Environmental Chemistry Laboratory (ECL) in Mississippi, USA, and the FDA Arkansas Regional Laboratory. Nine of 15 samples contained CDD/CDF (DF) at low levels, ranging from 0.4 to 22.5 ppt TEQ, with 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD) contributing the most to the sample TEQ.8 For comparison, the ball clay from the 1997 investigation contained TEQ concentrations over 1000 ppt and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was the primary congener contributing to the sample TEQ. Together with EPA, CVM initiated a survey in 2000 where 47 feed samples were collected. This survey is the subject of this paper, but analytical data will be presented on only 44 samples. In 2001, CVM continued its study of animal feeds by requesting that 50 samples of oilseed meals, fat-soluble vitamins, complete feeds, milk products, minerals, and wood products be collected for DFP analysis. Results from the 2001 survey may be available during 2002.