Introduction
Dioxins are a family of compounds that share certain chemical structures and biological characteristics. There have been concerns over the years about the potential health impacts of dioxins found in the environment and in the food supply. However, recent reports indicate that there are no known established health effects in people resulting from typical dioxin exposure through diet and environment.
Additionally, because of the interest in understanding the effects of dioxins by government, public health groups, industry, and others, significant coordinated regulatory and voluntary efforts have reduced human exposure from industrial processes. According to EPA data, dioxin emissions from all quantified sources have declined by at least 90 percent over the past two decades.
Dioxins are colorless, odorless organic compounds containing carbon, hydrogen, oxygen and chlorine. They are produced naturally from volcanoes, brush and forest fires, and from traditional human activities such as manufacturing, incineration, and exhaust emissions. Many of the emissions from these human activities have been reduced including paper and pulp bleaching. Burning household trash and fuels like coal, wood, or oil also forms dioxins.
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Exposure to Dioxins
Dioxins are ubiquitous in the environment and found in air, water and soil in all areas of the world. Dioxins are frequently detected at concentrations in the part per trillion (ppt) range. (A part per trillion is roughly equivalent to a drop of ink in an Olympic-size swimming pool.) In the United States, industrial sources of dioxins released into the environment have decreased significantly over the past 20 years. Today, studies indicate that the largest sources of these chemicals in the U.S. are backyard trash burning and forest fires.
Although dioxin exposure can come through industrial exposure by contact with the skin or inhalation, overall, skin contact and breathing represent very small sources of dioxin exposure. Dioxins can be deposited on plants and taken up by animals and fish as they feed and thus, may enter the food chain. Dioxins have a high affinity for fatty substances and are found in fat tissue. It is estimated that 95 percent of human exposure to dioxins comes from the diet through food and human breast milk.
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Dioxins, Diet, and Health
Dioxins have been the subject of intensive scientific research and environmental controls since the 1970s. To date, no clearly established health effects associated with exposure to current, low normal levels of dioxins have been identified. Very high levels of dioxin—hundreds of times greater than natural levels—are known to cause a reversible skin condition known as chloracne. Chloracne has been documented in people who are accidentally exposed to dioxin in industrial settings, or intentionally poisoned.
Some studies of industrial worker groups have suggested a small increase in cancer rates in persons subjected to unusually high dioxin exposures over many years. Studies of high level exposure also indicate that some biochemical changes, such as enzyme and hormone levels, may be induced by such exposures.
Typical dietary exposure has not resulted in high dioxin levels. However, 95 percent of human exposure to dioxins comes from the diet through food, and from human breast milk. Typical dietary exposure, even over the course of many years, is still far below that which might occur in accidental occupational exposures.
Following the advice in the 2005 Dietary Guidelines for Americans will help consumers reduce exposure to dioxins if desired. Consumers should choose a balanced diet high in fruits, vegetables, whole grains, non-fat and low-fat milk and milk products, and lean proteins. These choices are consistent with maintaining weight and overall health and reducing the risk for chronic diseases such as obesity and diabetes. These recommendations are supported by leading nutrition and health authorities including the American Dietetic Association. They emphasize important dietary advice for overall health, such as reduced intake of saturated fat and total fat, which can also reduce exposure to dioxins through diet. Consumers should not eliminate any one food or food group in an effort to reduce saturated fat or exposure to dioxins. Eliminating foods or food groups could lead to nutrient inadequacies and significant health consequences because each food group provides at least one nutrient and provides substantial contributions of many other nutrients that are important for good health. For example, public health authorities recognize that many Americans, particularly females, are not meeting daily requirements for calcium. Eliminating dairy products could increase the incidence of osteoporosis among this population.
Dioxins are known to pass from the mother’s body to the infant during breastfeeding. Because dioxins can be found in human breast milk, some questions have been raised about whether it is safe to nurse. But many health experts continue to recognize that breastfeeding provides numerous nutritional, immunological, and other benefits to infants in the first months of life.
Scientists continue to study dioxins to ensure there is no harm to humans through dietary exposure, and industry and government continue efforts to reduce dioxin levels in the environment.
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Minimizing Dietary Exposure to Dioxins
Studies show there is no cause for alarm from potential health issues concerning dioxins in the diet. However, following the 2005 Dietary Guidelines for Americans recommendations may result in multiple health benefits, including reduced dioxin exposure. Choosing a balanced diet that is low in saturated fats and total fats helps consumers minimize any potential exposure to dioxin from food because dioxins are found mostly in animal fats (due to the fat soluble properties of the dioxin compound). These guidelines include the recommendations to:
- Choose leaner cuts of beef, pork, and poultry; trim the fat and remove skin from chicken before cooking
- Choose non-fat and low-fat milk and milk products
These strategies help lower the intake of saturated fats and total fats and therefore help reduce the risk of exposure to dioxins.
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U.S. Efforts to Reduce Dioxins in the Environment
In the United States, industrial sources of dioxins released into the environment have decreased significantly over the past 20 years. Efforts by industry, municipalities, and local and federal government regulatory agencies to cut back industrial processes have successfully reduced levels of dioxin released in the environment from industrial and community sources. The major reductions in industrial sources of dioxins have led to significant decreases in the environment, and thus to decreases of dioxins found in the food chain.
The U.S. Environmental Protection Agency (EPA), along with state governments and industry have collectively made significant reductions in the levels of dioxins released into the environment, which is the most effective way to reduce dioxin levels in food. The EPA, working closely with industry, has taken aggressive actions by placing strict regulatory controls on all of the major industrial sources of dioxins. According to EPA data, dioxin emissions have been reduced by at least 90% from 1987 levels.
Source: EPA - The Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States: The Year 2000 Update
Since the mid-1990s, dioxin levels in meat and poultry have also declined significantly. Also, a recent study by the Centers for Disease Control and Prevention (CDC) confirms that dioxin levels in human tissues are very low and that human blood levels of dioxins have decreased by more than eighty percent (80%) since the 1980s. These data mirror the documented declines in dioxin environmental levels.
Trends in Dioxin Levels in Lake Sediment, Archived Food and Human Tissue*
Dioxin Level in Parts per Trillion
Note: Click on image to view larger version.
Source: Based on Hagenmeier and Walczok (1996), Ferrario et al., (1998) and Lorber (2002)
*Sediment core samples reflect dioxin in the environment averaged over a time span. Food samples are retrieved from museums or other storage. Tissue data are human blood and fat. Food data (non-detects are evaluated as one-half the detection limit) are multiplied by 10 and tissue data by 0.3 to fit the scale.
Study after study demonstrates falling dioxin levels in humans, food, soils, and sediments. Today studies indicate that the largest amounts of these chemicals in the U.S. are a result of uncontrolled burning of household trash and forest fires. The EPA is also working to discourage the practice of backyard trash burning, currently estimated to be the single largest source of dioxins to the environment. Information about the hazards of open trash burning and alternative methods for trash disposal are available in a series of brochures ( found at http://www.epa.gov/msw/backyard/pubs.htm) produced by the EPA. It is important to note that humans will always be exposed to some low level of dioxins because there are natural sources of these compounds such as dioxins produced in forest fires and volcanoes.
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Federal Government Efforts to Minimize Dioxin Levels in Foods
The U.S. Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA) monitor dioxin levels in foods and animal feeds, and conduct investigations whenever a food or animal feed has levels above established natural levels.
- In 1999, the FDA’s Center for Food Safety and Applied Nutrition (CFSAN) began annual monitoring for dioxins in foods collected in its Total Diet Study (TDS), a yearly program that determines levels of various contaminants and nutrients in food. TDS analysis is used to determine human exposure levels; if increased dioxin sources are detected, the FDA removes the source.
- The TDS indicates that dietary intake levels of dioxin-like compounds are 90% lower than those of the 1970s, and 50 percent lower from the mid-1990s. The TDS report can be accessed at: http://www.cfsan.fda.gov/~lrd/dioxdata.html.
In May 2000, FDA's Center for Veterinary Medicine (CVM) initiated a preliminary national survey of dioxin-like compounds in animal fats and feed. The purpose of this survey was to determine background levels of dioxin-like compounds in fatty and other feed ingredients commonly used in animal feeds. In addition to reducing environmental levels and monitoring foods, the government is continuing research efforts to better understand how dioxins get into the food supply and to identify ways for further reducing the level of dioxins in food.
The USDA’s Food Safety and Inspection Service periodically monitors levels of dioxin-like compounds in various livestock. Levels of these compounds have declined in all livestock surveyed. Average declines between the survey periods 1994 – 1996 and 2002 – 2003 range from 33 percent (steers and heifers) to 81 percent (market hogs). The June 2005 report announcing those data can be accessed at: http://www.cfsan.fda.gov/~lrd/dioxdata.html.
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Bottom Line
Humans will always be exposed to some low level of dioxins because of the natural sources released into the environment. To date, there have been no established health effects in people resulting from typical dioxin exposure through diet and environment. Americans should continue to enjoy a variety of foods from all five food groups, including lean meats, poultry and fish, as well as low and no fat milk and dairy products as outlined by the 2005 Dietary Guidelines for Americans. In addition, many experts agree that breast-feeding remains the best source of early nutrition for infants, with numerous health benefits for both baby and mother.
Americans enjoy one of the safest food supplies in the world. The federal government, regulators, educators and physicians can all agree that a well balanced diet, rich in a variety of fruits and grains and enjoyed in moderation, is key to a healthful lifestyle.
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Other Resources
Centers for Disease Control and Prevention (CDC)
Third National Report on Human Exposure to Environmental Chemicals:
http://www.cdc.gov/exposurereport/3rd/default.htm
http://www.cdc.gov/exposurereport
Chlorine Chemistry Council
Dioxin Facts
http://www.dioxinfacts.org
Dietary Guidelines for Americans, Sixth Edition (2005)
US Department of Health and Human Services
http://www.health.gov/dietaryguidelines
US Department of Agriculture
Dioxins and Dioxin-Like Compounds In the U.S. Domestic Meat and Poultry Supply
http://www.fsis.usda.gov/PDF/Dioxin_Report_0605.pdf
Food and Drug Administration (FDA)
Center for Food Safety and Applied Nutrition
Interagency Working Group on Dioxin (IWG)
Questions and Answers about Dioxins, July 2006
http://www.cfsan.fda.gov/~lrd/dioxinqa.html
MyPyramid Food Guidance System
http://www.mypyramid.gov
National Academies of Science
Health Risks from Dioxin and Related Compounds:
Evaluation of the EPA Reassessment
http://www.nationalacademies.org/morenews/20060711c.html
U.S. Environmental Protection Agency (EPA)
National Center for Environmental Assessment
Dioxin and Related Compounds
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=55264
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References
Ferrario, J., Byrne, C., Dupuy, A., Winters, D. L., Lorber, M., Anderson, S. (1998). Organohalogen Compounds, 35, p. 29-32.
Food and Drug Administration (October 2004). Questions and Answers About Dioxins [accessed Nov. 11, 2005; Dec. 8, 2005] http://www.cfsan.fda.gov/~lrd/dioxinqa.html#f1
Hagenmeier, H. and Walczok, M. (1996). Time trends in levels, patterns and profiles for PCDD/PCDF in sediment cores of Lake Constance. Organohalogen Compounds, 28, p. 101-104.
Institute of Medicine of the National Academies, Committee on the Implications of Dioxin in the Food Supply (2003). Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, D.C.: The National Academies Press.
Lorber, M. (2002). A pharmacokinetic model for estimating exposure of Americans to dioxin-like compounds in the past, present, and future. The Science of the Total Environment, 288, p. 81-95.
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