It's Your Health
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Dioxins and furans are common names for toxic chemicals that are found in very small amounts in the environment, including air, water and soil. As a result of their presence in the environment, they are also present in some foods.
Exposure to dioxins and furans has been associated with a wide range of adverse health effects in laboratory animals and humans. The type and occurrence of these effects typically depend on the level and duration of exposure.
There are 210 different dioxins and furans. All dioxins have the same basic chemical "skeleton," and they all have chlorine atoms as part of their make-up. Furans are similar, but have a different "skeleton". These substances vary widely in toxicity. The one considered most toxic is referred to as 2,3,7,8-tetrachlorodibenzo-p-dioxin, or simply TCDD.
The biggest source of dioxins and furans in Canada is the large-scale burning of municipal and medical waste. Other major sources include:
Dioxins can also be produced from natural processes, such as forest fires and volcanic eruptions. Most dioxins are introduced to the environment through the air. The airborne chemical can attach to small particles that can travel long distances in the atmosphere, which means that Canadians may also be exposed to dioxins and furans created in other countries.
These substances work their way up the food chain by moving into and remaining stored in body fat. Because of this, people actually take more dioxins and furans into their bodies through food than through air, water or soil. Ninety per cent of people's overall exposure to dioxins is estimated to be from the diet. Meat, milk products and fish have higher levels of dioxins and furans than fruit, vegetables and grains.
Scientists have studied the effects of dioxins and furans on laboratory animals. They have also researched the health effects on people exposed to dioxins through industrial accidents, contaminated food, and occupational exposure to certain herbicides prior to improved manufacturing processes that have reduced these contaminants.
The studies show that dioxins and furans have the potential to produce a range of effects on animals and humans. Health effects associated with human exposure to dioxins include:
It is important to remember that with all toxic substances, including dioxins, the risk of health effects depends on many factors, including:
These issues are very complex. Scientists do not have all of the answers, but they agree that exposures to dioxins and furans should be kept as low as possible.
For most people, about 90% of overall exposure to dioxins comes through diet. The Joint Expert Committee on Food Additives, an expert group of the World Health Organization and the Food and Agriculture Organization of the United Nations, has set a "tolerable monthly intake" level for dioxins, furans and similar substances.
The "tolerable" level (meaning no serious health effects are expected) is 70 picograms per kilogram of body weight / month. This is roughly 2.3 picograms per kilogram of body weight / day. A picogram is one-trillionth of a gram.
Studies done between 1998 and 1999 in two Canadian cities showed that the average dietary intake of dioxins, furans and similar substances was 0.62 picograms per kilogram of body weight /day. This is well within the level considered tolerable by Joint Expert Committee on Food Additives.
If you are concerned about exposure to dioxins and furans, consider taking the following steps:
By taking these steps, you can reduce your family's exposure to dioxins and furans, and help to limit the overall release of these substances into the environment.
The Government of Canada is working to control, and if possible, eliminate releases of these substances into the environment to help protect Canadians against harm from dioxins and furans. Actions to date include:
These efforts are working. The latest inventory shows a 60 percent decrease since 1990 in the overall release of dioxins and furans from sources within Canada. Also, the levels of dioxins and furans in Canadian human milk, which were already low, went down by roughly 50 percent between the 1980s and the 1990s. It is expected that levels of dioxins in various sources in Canada will continue to decline in conjunction with ongoing pollution prevention and control activities.
The Government's work to control sources of dioxins and furans in Canada continues. A federal-provincial task force has updated the inventory of sources for these substances, and Canada-wide standards are being established to address releases from remaining manufactured sources. In addition, the Government is continuing to carry out food monitoring activities to identify, control and if possible, eliminate previously unknown sources of dioxin contamination.
Also, Health Canada is doing a comprehensive reassessment of the risks posed by dioxins. In the meantime, Health Canada has adopted the Joint Expert Committee on Food Additives' tolerable monthly intake for dioxins as a guideline for Canadians.
For more information, contact:
Health Canada's Management of Toxic Substances Division
Room A724, Jeanne Mance Building #19
Ottawa, ON K1A 0K9
Telephone: (613) 957-3127
Health Canada's Food Program Web site.
Environment Canada - Persistent Organic Pollutants - POPs
For tips on safer ways to burn wood, visit Natural Resources Canada, Burn it Smart.
For more on the health effects associated with exposure to dioxins, see the following:
The World Health Organization's Safety Evaluation of Certain Food Additives and Contaminants.
The World Health Organization's Dioxins and their effects on human health.
The U.S. Environmental Protection Agency's Draft Dioxin Reassessment.
United States National Academy of Sciences Report, Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure.
For information on herbicide use at National Defence, see the National Defence Web site.
For additional articles on health and safety issues go to the It's Your Health Web site.
You can also call toll free at 1-866-225-0709 or TTY at 1-800-267-1245*.
ę Her Majesty the Queen in Right of Canada,
represented by the Minister of Health, 2005
Updated: September 2005
Original: November 2001