involved about 100 scientists including non-EPA scientists used
to peer review each chapter as it developed. EPA management decided
the question of dioxin's risk had been marked by considerable
controversy for more than a decade, we should pursue a process
that would achieve scientific consensus on this issue... As a
first step, it would be conducted as a cooperative effort, written
by both EPA scientists and external scientists and peer-reviewed
by scientists outside the Agency who were experts on dioxin. We
hoped this would help ensure not only that the most current, most
scientifically accepted information was used, but also that all
scientific views would be heard and debated.
comments were invited, three peer-review workshops were held and
the drafts of each chapter, most of which were authored or co-authored
by outside scientists, were reviewed and revised by a panel of
scientists from other government agencies.
1994 a draft report was released and open to public comment and
in 1995 the final report was published. The report stated that:
is adequate evidence from studies in human populations as well
as in laboratory animals and from ancillary experimental data
to support the inference that humans are likely to respond with
a plethora of effects from exposure to dioxin and related compounds.
significant in this analysis is the heightened concern about
noncancer effects in humans, including disruption of the endocrine,
reproductive, and immune systems, as well as dioxin's impact
on the developing fetus, which may occur in some cases at or
near background levels.
report referred to studies that had found "decreased sperm count
in men, higher probability of endometriosis in women, weakened
immune systems, and other health problems" as a result of dioxin
exposure in the general population at levels already found in
the food supply. The report claimed that current background levels
of dioxins could be posing a risk of one additional death in every
thousand or one in every ten thousand, even though as little as
30 pounds of dioxin may be released in the US each year.
EPA study also examined the sources of dioxin in the environment
and the ways in which people are exposed. It concluded: "The presence
of dioxin-like compounds in the environment has occurred primarily
as a result of anthropogenic practices", that is human activities.
It based this conclusion on the sampling of tissue of ancient
humans and sediments in lakes near industrial centres in the US
which showed low levels of dioxins prior to 1920.
study found that most dioxin is carried through the air and taken
up by plants, which are in turn eaten by fish and animals which
bioaccumulate the dioxin in their fatty tissues. By the time humans
eat the fish, beef, dairy products etc, the dioxin is far more
concentrated than it originally had been in the environment and
it accumulates in the fatty tissues of humans. Ingestion of dioxin
via food is a far more significant means of exposure than breathing
in polluted air. The report noted that the major source of dioxin
was incinerators, and that sources such as chemical manufacturing
could be significant but that there was insufficient data on them
to be able to say.
...back to top
EPA Reassessment Reports
EPA, 1995, Estimating
Exposure to Dioxin-Like Compounds.
EPA, 1995, Health
Assessment for 2,3,7,8-Tetrachlorodibenzo-p-Dioxin and Related
Peter, 1994, Dioxin
Reassessed - Part 1,
Rachel's Hazardous Waste News, No. 390.