The debate about the human health effects of dioxin continues, even as the levels of dioxin measured in people have continued to decline from their peak 30 to 40 years ago. Increasingly, scientific studies have shown that humans are less sensitive to the effects of dioxin than some laboratory animals.
Dow’s Position
While Dow acknowledges that studies have shown that dioxin (specifically, 2,3,7,8-TCDD) can cause a variety of health effects in laboratory animals exposed to high levels of dioxin normally not encountered in the environment, we believe that there is a lack of evidence of humans having experienced similar health effects. Most other dioxins are considered to be less toxic than 2,3,7,8-TCDD. Human exposure levels have in some groups been well above those causing effects in laboratory animals. However, the only consistently demonstrated health effect has been chloracne — a temporary skin condition which can be severe in some cases. This conclusion is supported by the findings of Dow’s studies on its own exposed employees and the collective evaluation of human health data.
A key consideration in evaluating potential health risk is exposure. According to the U.S. Environmental Protection Agency (EPA), the primary way people in the general population are exposed to dioxin is through eating meat, fish and dairy products that have been exposed to background levels of dioxins and furans in the soil, on vegetation, in water, and in some commercial animal feeds. Over time, we can accumulate dioxin in the fatty tissues of our bodies. Dioxin levels in people of all ages in the U.S. continue to decline and are seven-fold lower now than they were 30 years ago, through a combination of government regulations and voluntary industry efforts. In particular, children born today will accumulate far lower levels of dioxin than those born 30 years ago. As dietary background levels continue to decline, the margin of exposure (or difference between higher exposures required to cause the most sensitive effect in laboratory animals and exposures to the general public) will increase, thus further reducing the potential risk of dioxin effects. Adding to the enlarging margin of exposure is the consideration of lower sensitivity of humans to dioxin contributing to risk reductions of even greater magnitudes. However people will always have dioxin levels in their bodies, because it is generated through a number of human activities involving combustion, and natural sources, such as forest fires and volcanic activity.
In 2006, the University of Michigan reported the results of a two-year study of dioxin and furan and PCB exposure in the Midland-Michigan area and along the Tittabawassee River downstream from Dow manufacturing operations. Dow provided a “no stings attached” grant to the University of Michigan to conduct a human dioxin exposure study. To review the findings, please go to http://www.sph.umich.edu/dioxin/. While the results of this study are still being analyzed and reported, the initial findings from this study show little relationship between soil levels and levels in people living along the Tittabawassee River and in Midland. This finding should be reassuring and demonstrates that contact with contaminated soil does not contribute significantly to dioxin concentrations in humans. “The most important factor related to levels of dioxins in people’s blood is age,” (according to the University of Michigan study) and other factors such as amount of body fat and diet.
For more information on human levels of dioxin, please see the U.S. Centers for Disease Control and Prevention (CDC)’s Third National Report on Human Exposure to Environmental Chemicals.
