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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Veterinarian Newsletter September/October 2001 Volume XVI, No V


In July 1997, after lengthy investigation by several Federal and State agencies, the source of the dioxin contamination in broilers was traced to a feed ingredient called ball clay. Ball clay was used as an anti-caking agent in soybean meal, in other feed components, and in complete animal feeds. CVM worked cooperatively with the affected industries across the nation to halt any further distribution and use of the feed known to be contaminated with dioxin. Ball clay is no longer accepted for use as a feed ingredient by the Association of American Feed Control Officials.

In FY 1998, FDA initiated steps to determine whether other anti-caking agents were contaminated with dioxin, similar to the findings in ball clay. Industry associations met with CVM to determine the type of information needed, which resulted in a compilation of industry sampling of anticaking agents for dioxins. FDA, with analytical assistance from EPA, also surveyed anti-caking ingredients for the presence of dioxins. As a result of this survey, CVM prepared a revised guidance document for industry (#98) entitled "Dioxin in Anti-caking Agents Used in Animal Feed and Feed Ingredients" (Notice of Availability published in the Federal Register on April 19, 2000, Vol. 65, No. 76, Pages 20996-7).

FDA is a public health agency and is concerned about human exposure to dioxin and dioxin-like compounds. Certain dioxin, furan and PCB (polychlorinated biphenyl) congeners comprise a family of about 30 compounds that act by a similar mechanism. This family of compounds accumulate in the fat of humans and animals and produce a broad range of adverse effects including, but not limited to, enhanced tumorigenicity, enzyme induction, immune suppression, and a wasting syndrome. The diet is considered the primary route by which humans are exposed to these compounds and animal fats may be the greatest contributor to the dietary exposure. The remainder of this article summarizes CVM's recent efforts to obtain additional data on background levels of dioxin and dioxin-like compounds in animal feed.


On May 22, 2000, CVM issued a field assignment entitled "Preliminary National Survey of Dioxin-like Compounds in Animal Fats, Animal Meals, Oilseed Deodorizer Distillates, and Molasses." That assignment examined the feed ingredients suspected of containing the highest dioxin levels (fish meal, oilseed deodorizer distillates, animal fat, and meat and bone meal). It also looked at ingredients where air deposition (corn), uptake from soil (beet molasses) and fire during the harvest (cane molasses) were likely a major pathway of dioxin contamination. CVM is hopeful the EPA lab can complete the analyses on the 47 samples collected in the next few weeks.

On July 3, 2001, CVM issued a follow-up assignment entitled "Preliminary National Survey of Dioxin-like Compounds in Oilseed Meals, Fat-soluble Vitamins, Complete Feeds, Milk Products, Minerals, and Wood Products." This assignment is similar to the previous assignment, except the FDA's Arkansas Regional Laboratory will conduct the analyses and the feed ingredients will be different. The feed ingredients selected in this assignment were considered to be in the second tier regarding likelihood of elevated dioxin levels. CVM realizes it is more of an art than a science when it comes to prioritizing samples for dioxin analysis, but believes it is important to discuss the major reasons why these feeds were selected.

There were several factors involved in the selection of complete feed, oilseed meals, fat-soluble vitamins, milk products, mineral products, and wood products. These factors include, but are not limited to, past history of dioxin contamination, the likelihood the ingredient would be used in a ration, the amount typically used in a ration, the percentage fat, the likelihood of having a dioxin contamination from the manufacturing process, the likelihood of having elevated dioxins at the mine of origin of the ingredient, and the need to be able to compare the results from a single ingredient with levels typically found in complete feeds.

There is very little information on background levels of dioxins in complete feed. This information will be useful if the FDA has to consider taking regulatory action on an individual feed ingredient or the total ration.

Oilseed meals are commonly used at levels greater than 10% of the diet in many animal species. While oilseed meals are primarily utilized for their high levels of crude protein (about 25-50%), they also contain some fat (about 1.5-8.0% depending an whether the fat is solvent or mechanically extracted). The oilseed meals could also potentially pick up dioxins during the manufacturing process or when anti-caking agents are mixed with them.

Additional information on dioxins in fat-soluble vitamins (A, D, E, and K) is important for the following reasons: 1) the fat-soluble vitamins are commonly added at low levels to most animal diets, 2) dioxins are fat-soluble compounds, and 3) there is a wide diversity in how fat-soluble vitamins are derived. Some of these vitamins are synthesized. Some are derived from plants and some come from animals.

While milk and milk products for human consumption have been tested for dioxins by the FDA's Center for Food Safety and Applied Nutrition, there is little, if any, data on dioxins in milk products used in animal feeds. Dried whole milk should contain a minimum of 26% fat and condensed buttermilk and dried cheese often contain about 15-25% fat. In addition to these "fatty" milk products, there are several milk products (casein, whey, skimmed milk, etc.) with low levels of fat (around 1%). Since dioxins are fat soluble compounds, a slightly greater emphasis will be placed on the "fatty" milk products than on the "non-fatty" ones.

The potential concerns with mineral products are two-fold. First, they may be like ball clay and contain high dioxin levels from their mine of origin. Second, the manufacturing process, transport and/or prior use of these mineral products may have introduced some dioxin contamination.

The potential concern with wood products (cellulose, lignin, etc.) is that the starting material could have been treated with pentachlorophenol (PCP). PCP was a wood preservative whose uses were greatly curtailed because of its high dioxin contamination. Elevated dioxin levels were recently found in choline chloride from the EU and additional analyses indicated that a carrier, pine sawdust, was the likely source of the contamination. The congener pattern in the pine sawdust was consistent with prior PCP treatment.

There are no tolerances established by the FDA for dioxins and furans in food or feed. Temporary tolerances for PCBs for feed and foodstuffs can be found in 21 CFR 109.30 and 509.30. FDA, in conjunction with the USDA, EPA, CDC and the European Union, is addressing both international and domestic dioxin, furan and PCB concerns.