This research project is a data collection effort used to support research and regulatory policy regarding dioxin-like compounds.

Project Status

The mass balance study (Phase 1) is complete. Results were reported in 2000 and 2002 at the annual international dioxin conference, and conference proceedings articles were also prepared and published. The study to monitor for dioxin-like compounds in minor components of animal feed (Phase 2) is completed. Results of this study were reported on and published in conference proceedings, during the 2002 international dioxin conference. The third phase of this project, to monitor for dioxin-like compounds in major feed components in operating dairy research facilities around the country, is underway. Samples have been taken and are currently in storage awaiting analysis. Study plans have been developed for possible future sampling of animal feeds for beef cattle, pork, and poultry.

Project Start Date


Project Completion Date (Actual/Projected)



The purpose of this study is to measure the levels of dioxin-like compounds in the feeds of terrestrial food animals - cattle, swine, and poultry - and to understand their contribution to the dioxin-like levels found in the animals. It is an ongoing effort involving several phases, three of which can be described at this point. The first phase has been completed, and it was a mass balance study of dioxin-like compounds in a lactating cow. The second phase is also completed, and it was a study on the levels of these compounds in the minor components of animal feeds. The third phase is a more systematic sampling of major feed components in dairy operations. It began in 2002 and is nearing completion.

The first phase was conducted during 1997 and 1998. This phase was a study measuring the input of dioxins to the lactating cow via their feed and the output through their milk and feces. The primary purpose of the study is to confirm that, under carefully controlled background conditions, feed is the primary intake vector for dioxins in cows, and that feces and milk is the primary output vector. The secondary purpose was to develop relationships between dioxins in feed and dioxins in milk. The results confirmed that feed was the principal input vector to the lactating cows. Principal results from this study were presented at the annual international dioxin conference in the falls of 2000 and 2002. Conference proceedings articles were also prepared and published.

The second phase began during 2000 and was completed during 2002. This was a limited study targeting minor compounds of animal feeds. Minor components of animal feeds can sometimes prove to be major contributors of dioxin to the animal. This was the case when it was found that ball clay, added as an anti-caking agent to chicken feed, led to extremely elevated levels in chickens, found in a survey jointly conducted by EPA and USDA in the mid-1990s. The sampling of these minor components was conducted in conjunction with the Center for Veterinary Medicine of the Food and Drug Administration. EPA provided general oversight and designed the study, and FDA has provided field personnel to sample the feed components. A total of 44 samples were collected from around the country and delivered to the EPA laboratory in Bay St. Louis, Missouri. Analysis of these samples occurred during 2001, and the reporting of this information in the annual international dioxin conference occurred during 2002.

The third major phase of this project began during 2002. This phase entails the collection of full mixed feed and feed components at government (including federal government and land grant University) research facilities where lactating cows are being maintained in a manner similar to commercial operations in terms of feeding, housing, and milking practices. The purpose of this phase is to more comprehensively identify which components of animal feeds, at least for the production of milk and dairy products, are most responsible for dioxin inputs to the animal.

The analysis of total mixed feed and the major feed components was completed in 2004 and reported on at the annual dioxin international conference. The primary findings were that the feed concentrations were generally lower than expected, at less than 0.10 ppt TEQ, and that the major components (hays, grasses, etc.) had the highest concentrations and contributed the most to the TEQ of the mixed feed. The analysis of minor components was completed in 2006 and the results reported at the annual international dioxin conference. While most minor components were low in concentration, similar to the major components, one minor component had a high concentration at 39ppt TEQ, and it was found to effectively double the overall concentration of the mixed feed. "A manuscript on the dairy feed study was published in 2007 in the Journal of Agriculture and Food Chemistry". peer-reviewed literature in the fall of 2006. This overall research effort supports the Agency's efforts to understand how Americans are exposed to dioxin-like compounds, and what the opportunities are for intervention in food chain to reduce this exposure.