Dioxins and Furans: The Health Hazards

Dioxins And Furans: The Health Hazards

by Todd Paddock, Academy of Natural Sciences July, 1989

Dioxins have caused a great deal of concern because they have been found in many places and are extremely toxic. Furans are similar chemicals and are often found with dioxins.

Although there are several hundred dioxins and furans, most are only slightly toxic and some are nontoxic. A small number of dioxins and furans (the so-called "dirty dozen") are among the most toxic substances yet discovered. A single dose of 6 millionths of a gram of the most toxic dioxin or furan, called 2,3,7,8-TCDD, is lethal for a rat.

A great deal is known about the effects dioxins and furans have on animals because researchers can use laboratory studies, where they can control and experiment with the many factors that influence the effects of a substance on an animal.

Research on the health effects dioxins and furans have on humans is limited to follow-up studies of people who were exposed to dioxins and furans during industrial accidents or accidental contamination. After such accidents, the amount of dioxins or furans the persons were exposed to (the dose) can only be estimated, and is often completely unknown. Because of this, it is much harder to confidently identify the health effects these substances have for humans, especially over a long period of time and at different doses.

Trace levels of dioxins and furans have been found in the blood, breast milk, and fatty tissues of humans from many countries, including the U.S. and Canada. These findings indicate that the population in many parts of the world has been exposed to low levels of these compounds. It is believed that we take in most dioxins and furans through eating and breathing.

There is concern that the dioxins and furans in breast milk pose an especially high risk for breast-fed babies, because babies are tiny, growing rapidly, and often have breast milk as a sole source of nourishment. Workers in some industries are also exposed to relatively large amounts of dioxins and furans.

Based on what we know, dioxins and furans are more toxic to many animals than to humans. Fish, rodents, and other organisms are often exposed to greater amounts than are people, and many appear to be much more sensitive. Therefore, amounts of dioxins and furans that pose an acceptably small risk to human health may be a threat to other organisms.

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