August 26, 2003
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
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.