August 26, 2003


Tiffany Harrington


New Research Questions EPA's Dioxin Assumptions

Arlington, VA (August 26, 2003) - Research presented this week at the 23rd International Symposium on Halogenated Environmental Organic Pollutants and POPs, better known as Dioxin 2003, raises new questions about the potential carcinogenicity of dioxin and could challenge conventional assumptions that are currently used to define environmental policies.

Studies conducted by Exponent®, a widely recognized team of scientific consultants for businesses and government agencies, show that at high body levels, humans eliminate from their bodies traces of dioxin (2,3,7,8-TCDD-the most toxic of the dioxin compounds) three to five times faster than previously thought. Co-authors of the findings include researchers from the University of Montreal, University Milano and the U.S. Centers for Disease Control and Prevention (CDC).

Exponent's data analysis and modeling efforts cast doubt on the commonly used estimate of dioxin cancer potency, a cornerstone of the U.S. Environmental Protection Agency's (EPA's) draft health risk assessment of this substance. That estimate is based on the assumption of a relatively slow rate of elimination of dioxin from the human body.

"These new data sets will have a dramatic impact on commonly held assumptions about dioxin's potential to cause cancer in humans," said C.T. "Kip" Howlett, Jr., Executive Director of the Chlorine Chemistry Division of the American Chemistry Council.

The Exponent researchers studied blood samples of select groups of workers who experienced unusually high levels of exposure to dioxins in the workplace from the 1950s through the 1970s-exposure levels that are not experienced today. According to scientist Lesa Aylward, the new data demonstrate that the previous estimates may have underestimated actual occupational exposures at that time by factors of 5 to 10, or more. Underestimating these exposures has led to an overestimation of the cancer potency of dioxin by factors of 5 to 10 or more. These new findings could have far-reaching implications for the EPA's draft dioxin reassessment.

The Chlorine Chemistry Division of the American Chemistry Council supports independent research and other efforts that help us better understand the role that dioxins play in human health and the environment. The Chlorine Chemistry Division of the American Chemistry Council provided some resources for this research; more than half of the funding was provided by other sources. The new research is in review for publication.


The Chlorine Chemistry Division of the American Chemistry Council is a national trade association based in Arlington, VA representing the manufacturers and users of chlorine and chlorine-related products. Chlorine is widely used as a disease-fighting disinfection agent, as a basic component in pharmaceuticals and myriad other products that are essential to modern life.


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