February 27, 2012 - IMM@BUCT

news of the week
FEBRUARY 27, 2012 EDITED BY WILLIAM G. SCHULZ & SOPHIA L. CAI
DIOXINS,
ASSESSED AT LAST
POLLUTION: After years of study,
EPA sets safe level of exposure
to the most toxic congener
AFTER 21 YEARS of contentious scientific analysis,
the Environmental Protection Agency has
established a safe level of exposure to the most
toxic form of dioxin.
EPA set a safe daily dose of 0.7 picograms of
2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) per kilogram
of body weight. TCDD is the most potent congener
of the dioxins, which generally are unintentional
by-products of manufacturing processes involving
chlorine and burning of biomass or waste.
Eventually, this defined level of safe exposure will
affect the degree—and cost—of cleanups of soil and of
industrial air and water releases polluted with dioxins.
This category of chemicals consists of chlorinated
dioxins and furans and certain polychlorinated biphenyls.
These substances can trigger similar adverse
health effects, but their potencies vary.
The exact regulatory impacts of the agency’s determination
, which was released on Feb. 17, are as yet uncertain.
EPA’s new level “will serve as the cornerstone
of the agency’s initiatives to protect public health from
chemical contaminants and provide the necessary
guidance to states and public health agencies to minimize
dioxin exposure,” says Olga Naidenko, a senior
scientist with the Environmental Working Group, an
activist group.
The American Chemistry Council, an industry organization
that has invested much time and energy in
influencing EPA’s work on this assessment, calls the
agency’s conclusions “flawed.”
Lois Marie Gibbs, executive
director of the Center for Health,
Environment & Justice, an environmental
group that has focused
on dioxin issues for years, hails
the long-awaited completion of
the agency’s effort. “The American people,” she says,
“won a major victory against the chemical industry,
which has been working behind closed doors for decades
to hide and distort the truth about the dangers of
dioxin.”
Data in EPA’s annual Toxics Release Inventory indicate
that U.S. industry has slashed its releases of dioxins
in the past two decades (C&EN, Feb. 6, page 26).
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2,3,7,8-Tetrachlorodibenzo-p-dioxin
Backyard waste burning is the major source of dioxins
in the U.S. today.
The EPA limit is based on two studies. One found
adverse reproductive effects in men exposed to TCDD
as boys. The other found hormonal effects in infants
born to mothers who had high levels of exposure.
People are exposed to dioxins mainly by eating
meat, poultry, dairy products, fish, or eggs. However,
EPA claims that “most Americans have only low-level
exposure to dioxins,” adding that this “does not pose a
significant health risk.”
The agency’s document examines health effects
other than cancer from TCDD exposure. They include
chloracne, a severe skin disease producing acne-like
WWW.CEN-ONLINE.ORG 5 FEBRUARY 27, 2012
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lesions; developmental and reproductive effects; damage
to the immune system; hormonal disruption; and,
possibly, mild liver damage. The agency is still working
on a second document focusing on cancer hazards
of TCDD.
The assessment, which EPA launched in 1991 to
update a 1985 document describing
the cancer hazards of
TCDD, has faced many delays.
Throughout the years, polluting
industries—including chemical
companies—have faulted EPA’s
work. Community and public
health groups, meanwhile, have pressured the agency
to finish the review.
“After 21 years in the making, the dioxin assessment
is in the hands of the American people,” says Paul T.
Anastas, who oversaw release of the report on his final
day as EPA’s top scientist (C&EN, Jan. 16, page 9).
“I quite honestly never thought this report would
ever see the light of day,” Gibbs says. — CHERYL HOGUE
Backyard burning
of waste is now
the main source of
dioxins, according
to EPA.
SHUTTERSTOCK