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. According to the most recent EPA data, dioxin emissions from all quantified sources declined by approximately 90 percent between 1987 and 2000.
Dioxins are produced naturally from 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 significantly reduced. Most dioxin generated today is a natural byproduct of forest fires as well as rural trash burning, fireplaces and wood stoves. In fact, EPA data show backyard trash burning is the top source of dioxin emissions to the environment today.
Exposure to Dioxins
Dioxins are ubiquitous in the environment and are found in air, water and soil in all areas of the world. Dioxins are detected at trace concentrations in the part per trillion (ppt) ranges. (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.
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 also 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.
Dioxins, Diet, and Health
Dioxins have been the subject of intensive scientific research and environmental controls since the 1970s. 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 skin condition known as chloracne. Chloracne has been documented in people who are accidentally exposed to higher levels of dioxin in industrial settings, or who have been 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 over the course of many years is still far below that which might have occurred in historical occupational exposures or accidental situations.
The levels of dioxins found in humans have declined significantly as well. Biomonitoring surveys conclude that the amount of dioxins found in human blood has declined at a similar rate to that found in the environment. According to the December 2009 Center for Disease Control (CDC) Fourth National Report on Human Exposure to Environmental Chemicals: Dioxin levels in human blood are very low. The level of dioxins found in humans has declined by more than 80 percent since the 1980s.
Following the advice in the 2005 Dietary Guidelines for Americans will help further reduce exposure to dioxins. It recommends a balanced diet rich 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. The guidelines also emphasize important dietary advice for overall health, such as reduced intake of saturated fat and total fat from animal sources, which can also reduce dietary exposure to dioxins. 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 also 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. Many health authorities including the World Health Organization (WHO) continue to recognize that breastfeeding provides numerous nutritional, immunological, and other benefits to infants in the first months of life. The benefits from breast feeding outweigh the potential theoretical risks from dioxins in breast milk
Scientists continue to study dioxins to ensure there is no harm to humans through dietary exposure, and industry and government continue efforts to continually reduce dioxin levels in the environment.
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 from animal sources 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:
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 improve industrial processes have successfully reduced levels of dioxin released in the environment from industrial and community sources.
Today studies indicate that the largest amounts of dioxins in the U.S. are a result of uncontrolled burning of household trash and forest fires. The EPA discourages the practice of backyard trash burning, currently estimated to be the single largest source of dioxins to the environment.
Since the mid-1990s, dioxin levels in meat and poultry also have declined significantly. Studies by the U.S. Centers for Disease Control and Prevention (CDC) confirm that dioxin levels in human tissues are very low and that human blood levels of dioxins have decreased by more than 80 percent since the 1980s. These data mirror the documented declines in dioxin environmental levels. A recent study comparing data from three USDA surveys found a decreasing trend for dioxins in domestic meats and poultry. These downward trends are consistent with diminishing dioxin levels in the U.S. population as measured by the CDC between 1999 and 2004.
Trends in Dioxin Levels in Lake Sediment, Archived Food and Human Tissue*
Dioxin Level in Parts per Trillion
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 discourages 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 is available in a series of brochures produced by the EPA and found at http://www.epa.gov/epawaste/nonhaz/municipal/backyard/pubs.htm. 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.
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 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 most recent study, from October 2009 (http://origin-www.fsis.usda.gov/PDF/Dioxin_Report_1009.pdf), confirms the trend of continuing decline in levels of dioxins and dioxin-like compounds in domestic meats and poultry over the past decade.
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.
U.S. Centers for Disease Control and Prevention (CDC)
Fourth National Report on Human Exposure to Environmental Chemicals:
American Chemistry Council’s Chlorine Chemistry Division
Dietary Guidelines for Americans, Sixth Edition (2005)
US Department of Health and Human Services
US Department of Agriculture (USDA)
Dioxins and Dioxin-Like Compounds In the U.S. Domestic Meat and Poultry Supply
Food and Drug Administration (FDA)
Center for Food Safety and Applied Nutrition
Interagency Working Group on Dioxin (IWG)
Questions and Answers about Dioxins, updated September, 2008
Choose My Plate Food Guidance System
National Academies of Science
Health Risks from Dioxin and Related Compounds:
Evaluation of the EPA Reassessment
The University of Michigan Dioxin Exposure Study
U.S. Environmental Protection Agency (EPA)
National Center for Environmental Assessment
Dioxin and Related Compounds
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