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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Veterinarian Newsletter July/August 2000 Volume XV, No IV

Dioxins are a family of about 30 compounds that accumulate in the fat of humans and animals. They produce a broad range of adverse effects including, but not limited to, enhanced tumorigenicity, enzyme induction, immune suppression, and a wasting syndrome.

In a 1994 draft risk assessment, the U.S. Environmental Protection Agency (EPA) estimated that the diet was the primary source of dioxin exposure. EPA estimates that 95 percent of dioxin intake for a typical person comes through dietary intake of animal fats. Small amounts of exposure occur from breathing air containing trace amounts of dioxin on particles and in vapor form. Very little dioxin exposure occurs through water.

Dioxin is not created in foods, instead, it gets into foods from a variety of environmental sources. The relative contribution of major dioxin sources has changed significantly over time. Historically, commercial waste combustion, manufacture and use of phenolic herbicides, and chlorine bleaching of pulp and paper have resulted in the major releases of dioxins to air and water. Regulatory actions combined with voluntary industry measures have resulted in dramatic reductions in each of these source categories so none of them are expected to be major contributors of new dioxin-like compounds to the environment. The uncontrolled burning of residential waste and accidental fires at landfills are thought to be the largest currently unmanaged sources of dioxins.

The issue of dioxin in foods is not new, and it is not unique to the U.S. food supply. To date, the primary Federal government effort regarding dioxin exposure through the food supply has been to reduce the level of dioxins released into the environment. EPA has pursued the control and management of dioxin through each of its major program areas. These actions have placed strict regulatory controls on all of the major well-defined industrial sources of dioxin. As a result of EPA's efforts, along with effort by State government and private industry, known industrial emissions will be reduced by more than 90 percent by 2002.

Another effort has been a multi-Agency endeavor to look for and eliminate special instances of food contamination by dioxin. For example, in 1997 dioxin monitoring by the Federal government found unusual levels of dioxin in some farm-raised fish and poultry products. Once discovered, an investigation was launched immediately, which revealed that a particular food additive (a clay called ball clay used as an anti-caking agent in some soybean meal) was responsible. Through the regulatory authority of FDA, this food additive was immediately prohibited for use in any animal feed. Another example of an effort to eliminate special instances of food contamination by dioxin was when elevated levels of dioxin and PCBs were discovered in some Belgian animal products in 1999. FDA stopped import of those products into the United States.

A third effort is the ongoing research by FDA, EPA, and the U.S. Department of Agriculture (USDA) to better understand how dioxin gets into the food supply and to identify opportunities for reducing the level of dioxin in our food.

In June 2000, EPA released an Integrated Summary and Risk Characterization for dioxin and related compounds and a new technical chapter on dioxin Toxicity Equivalence Factors (TEF) for independent scientific peer review. In their draft reassessment, EPA concludes that dioxin is a "human carcinogen", and states that while emissions of dioxin have decreased from their peak levels in the 1970s they still may pose a significant cancer threat to some people who ingest the chemical through foods in a normal diet. EPA's draft Dioxin Reassessment is not considered finished until it goes through a review process including several levels of scientific evaluation and stakeholder comment.

In the past, FDA testing for dioxin has been limited to a few hundred samples a year, primarily of fish and dairy products from grocery stores and distribution centers. In addition, USDA and EPA have recently examined dioxins in a similar number of beef, pork, and poultry samples from across the country. FDA limited monitoring to these foods because dioxins occur at levels that are so low that they are hard to detect, and until recently, the methods used to detect dioxins were very expensive. Recent improvements in the science and cost of dioxin analysis have enabled FDA to broaden monitoring. FDA is now examining dioxins in 200 of the most commonly eaten foods, through the Total Diet Study. In addition, both FDA and USDA are developing plans to increase monitoring of the foods and animal feeds most likely to contain dioxins.

In May 2000, FDA's CVM issued an assignment to the Agency's field offices for a preliminary national survey of dioxin-like compounds in animal fats and meal, oilseed deodorizer distillates, and molasses. The purpose of this survey is to determine background levels of dioxin-like compounds in fatty and other feed ingredients commonly used in animal feeds.

As a public health agency, FDA is very concerned about human exposure to dioxin. For most people, following Federal dietary guidelines will result in reduced fat consumption and, consequently, reduced dioxin exposure. The Dietary Guidelines for Americans suggest choosing lean meat and low or fat free (skim) dairy products and increasing consumption of fruits, vegetables, and grain products.