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Dioxin in the U.S. Food Supply

Dioxin Emissions Declined 90 Percent between 1987 and 2000

The Chlorine Chemistry Division of the American Chemistry Council has tracked a steady decline in U.S. dioxin emissions to the environment over the past few decades using U.S. Environmental Protection Agency (EPA) data. Projected emissions reductions of 90% from 1987 levels reflect strict regulations placed on all of the known major industrial sources of dioxin (see Figure 1 below).

Dioxin here is defined as the totality of 7 dioxins and 10 furans. "TEQ" denotes "toxic equivalents," a quantitative measure of the combined toxicity of a mixture of dioxin-like compounds.

Source: U.S. EPA (Environmental Protection Agency). 2006. An inventory of sources and environmental releases of dioxin-like compounds in the United States for the years 1987, 1995, and 2000. National Center for Environmental Assessment, Washington, DC; EPA/600/P-03/002F. (http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=159286)

Falling Dioxin Emissions Levels are Reflected in Lower Sediment, Food and Human Body Levels

Since it is estimated that about 95% of human exposure to dioxin occurs through the diet, the dioxin content of foods is of particular public health interest. Environmental dioxin concentrates in dietary fat and subsequently in the fatty components of human blood. The Interagency Working Group on Dioxin (2003) states, "In the long-term, efforts to reduce dioxin in the environment should also reduce dioxin levels in the food supply" (p. 14). It is indeed an encouraging sign that as emissions to the environment have declined, lower sediment, food and human body levels of this substance have been documented, as illustrated in Figure 2.

Figure 2: Dioxin/Furan in Sediment, Food and Tissue

Researchers Find Dioxin Exposures and Body Levels Have Fallen Dramatically

In a recent review of historic, present and future dioxin risks, Hays and Aylward (2003) determined that the general public is experiencing a seven-fold lower level of dioxin exposure and body level today than it did 30 years ago. The authors project that body levels will continue to decline for at least the next two decades, even if intake levels remain constant and do not decline further over this time period. According to the authors, these encouraging trends in exposure ".do not indicate a public health basis for actions in reducing food levels and thus, general population exposures" (p.13).

Open Burning of Trash is Currently the Largest Source of Dioxin Emissions

With the decline in dioxin emissions from industrial sources, dioxin from non-industrial sources takes on greater significance. For example, backyard trash burning, a largely illegal, but common rural practice, is currently the single greatest source of dioxin to the environment (see Figure 3 below). Further efforts to curtail dioxin emissions should focus on this largely uncontrolled practice.

Figure 3

*OTHER category includes: diesel heavy-duty trucks, industrial wood combustion, diesel off-road equipment, EDC/VCM production, sintering plants, automobiles using leaded gasoline, land applied 2,4-D, iron ore sintering, oli-fired utilities, lightweight aggregate kilns that combust hazardous waste, petroleum refining, catalyst regeneration, cigarette smoke, boilers/industrial furnaces, crematoria, and drum reclamation.

Note: "Dioxin" here is defined as the totality of 7 dioxins and 10 furans. "TEQ" denotes "toxic equivalent," a quantitative measure of the combined toxicity of a mixture of dioxin-like chemicals.

Reality: Dioxin in Nature

Discussions of dioxin are incomplete without reference to the fact that there are natural sources of this family of compounds, such as forest fires and volcanoes. It may be assumed that humans have always been exposed to dioxins and that natural sources will continue to inject a small but finite "baseline" quantity of dioxin into the environment and, therefore, the food supply.

References

Hays, S.M. and Aylward, L.L. (2003). Dioxin risks in perspective: past, present, and future. Regulatory Toxicology and Pharmacology, 37, p. 202-17.

U.S. Interagency Working Group on Dioxin (January, 2003). Questions and Answers About Dioxins [On-Line] Available: http://www.cfsan.fda.gov/~lrd/dioxinqa.html (accessed 6-16-03).