>From the journal Science, Volume 290, Number 5490, Issue of 13 Oct 2000, p.
Just a handful of incinerators and factories in the United States spew much
of the dioxin that contaminates people in Nunavut, Canada, thousands of
kilometers to the north, a new study suggests. The study is the first to
track dioxin pollution in the Arctic to specific sources in North America.
Dioxins and related industrial chemicals are carried by weather patterns to
polar waters, where they wind up in the fat of animals via the marine food
chain. Arctic Inuits who eat dioxin-tainted whales, seals, and fish may
suffer health problems such as immune dysfunction, cancer, and developmental
delays, say researchers.
To pinpoint where the stuff comes from, a team led by Barry Commoner of
Queens College in New York City collected U.S., Canadian, and Mexican
government data from 1996 and 1997 that identify 44,000 dioxin sources from
urban incinerators to backyard trash fires. The researchers then plugged
their data into a National Oceanic and Atmospheric Administration (NOAA)
weather model that could predict the paths of dioxin puffs over the course
of a year. They found that a small fraction of sources accounted for most of
the dioxin measured at eight sites in Nunavut territory. More than one-third
of the dioxin found at Coral Harbour, for instance, came from just 19
sources, such as incinerators and ironworks in Iowa, Minnesota, and Indiana.
"This work is mighty new," says Richard Artz of NOAA's Air Resources
Laboratory. Similar studies have tracked acid rain in the northeastern
United States to Midwest power plants, Artz says, but they have not been
able to pinpoint specific sources. The results may influence negotiations
over an international treaty to curb persistent organic pollutants,
scheduled to finish later this year.
Science, Volume 290, Number 5494, Issue of 10 Nov 2000, p. 1071.
Panel Backs EPA Dioxin Assessment
by Jocelyn Kaiser
Outside scientists last week gave a thumbs-up to a long-awaited
Environmental Protection Agency (EPA) report finding that dioxin may be
causing health effects at levels close to background exposures. The massive
report is "by and large a very fair and balanced description," said
environmental scientist Morton Lippman of New York University, chair of the
subpanel assembled by EPA's Science Advisory Board to review the document, 5
years in the making. However, Lippman urged the agency to "clean up" some
conclusions, especially on cancer risks, which have been slightly downgraded
since a draft version was released last spring (Science, 16 June, p. 1941).
The favorable reaction comes as a relief to the EPA, whose 1994 draft dioxin
report was criticized sharply by a similar outside panel for ignoring
scientific uncertainties. The 2000 reassessment again finds that
dioxin--produced mainly by incinerators, smelters, landfill fires, and
backyard burning--and related chlorinated chemicals may be causing health
problems such as endometriosis, immune effects, developmental delays, and
While endorsing the report overall, the 17 reviewers--who included
academics, industry scientists, and private consultants--criticized some
sections. For example, some panel members took issue with EPA's decision to
assume that dioxin's effects are linear and have no threshold. Another
conclusion that sparked debate last spring--that the risk of cancer for the
most exposed individuals is between 1 in 100 and 1 in 1000, or 10 times
higher than in the 1994 report--has been softened: The report now describes
the highest risk as greater than 1 in 1000. Even so, panelist Roy Alberts,
an environmental health professor at the University of Cincinnati Medical
Center, called the report's cancer summary "too one-sided," because it
relies on worker studies that are "not decisive."
The review panel emphasized that dioxin's other effects are at least as
worrisome as those that are linked to cancer. The thorny issue of whether
steps should be taken to reduce dioxin in the food supply will soon be
considered by a National Academy of Sciences committee.
Charles A. Miller, III, Ph.D.
Associate Professor of Environmental Health Sciences
Tulane University School of Public Health and Tropical Medicine
1430 Tulane Ave.
New Orleans, LA 70112
(504)585-6942 rellim at tulane.edu
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