The Seveso Studies on Early and Long-Term Effects of Dioxin Exposure: A Review

Abstract

The industrial accident that occurred in the town of Seveso, Italy, in 1976 exposed a large population to substantial amounts of relatively pure 2,3,7,8-tetrachlorodibenzo-p-dioxin. Extensive monitoring of soil levels and measurements of a limited number of human blood samples allowed classification of the exposed population into three categories, A (highest exposure), B (median exposure), and R (lowest exposure). Early health investigations including liver function, immune function, neurologic impairment, and reproductive effects yielded inconclusive results. Chloracne (nearly 200 cases with a definite exposure dependence) was the only effect established with certainty. Long-term studies were conducted using the large population living in the surrounding noncontaminated territory as reference. An excess mortality from cardiovascular and respiratory diseases was uncovered, possibly related to the psychosocial consequences of the accident in addition to the chemical contamination. An excess of diabetes cases was also found. Results of cancer incidence and mortality follow-up showed an increased occurrence of cancer of the gastrointestinal sites and of the lymphatic and hematopoietic tissue. Experimental and epidemiologic data as well as mechanistic knowledge support the hypothesis that the observed cancer excesses are associated with dioxin exposure. Results cannot be viewed as conclusive. The study is continuing in an attempt to overcome the existing limitations (few individual exposure data, short latency period, and small population size for certain cancer types) and to explore new research paths (e.g., differences in individual susceptibility).

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The
Seveso
Studies
on
Early
and
Long-Term
Effects
of
Dioxin
Exposure:
A
Review
Pier
A.
Bertazzi,"l
laria
Bernucci,2
Gabriella
Brambilla,3
Dario
Consonni,4
and
Angela
C.
Pesatori3
1Research
Centre
for
Occupational,
Clinical
and
Environmental
Epidemiology
(EPOCA),
University
of
Milan,
Milan,
Italy;
2Postgraduate
School
of
Occupational
Health
and
Industrial
Toxicology,
University
of
Cagliari, Cagliari,
Italy
31nstitute
of
Occupational
Health,
University
of
Milan, Milan,
Italy;
4Clinica
del
Lavoro
L.
Devoto,
Istituti
Clinici
di
Perfezionamento,
Milan,
Italy
The
industrial
accident
that
occurred
in
the
town
of
Seveso,
Italy,
in
1976
exposed
a
large
population
to
substantial
amounts
of
relatively
pure
2,3,7,8-tetrachlorodibenzo-p-dioxin.
Extensive
monitoring
of
soil
levels
and
measurements
of
a
limited
number
of
human
blood
samples
allowed
classification
of
the
exposed
population
into
three
categories,
A
(highest
exposure),
B
(median
exposure),
and
R
(lowest
exposure).
Early
health
investigations
including
liver
function,
immune
function,
neurologic
impairment,
and
reproductive
effects
yielded
inconclusive
results.
Chloracne
(nearly
200
cases
with
a
definite
exposure
dependence)
was
the
only
effect
established
with
certainty.
Long-term
studies
were
conducted
using
the
large
population
living
in
the
surrounding
noncontaminated
territory
as
reference.
An
excess
mortality
from
cardiovascular
and
respiratory
diseases
was
uncovered,
possibly
related
to
the
psychosocial
consequences
of
the
accident
in
addition
to
the
chemical
contamination.
An
excess
of
diabetes
cases
was
also
found.
Results
of
cancer
incidence
and
mortality
follow-up
showed
an
increased
occurrence
of
cancer
of
the
gastrointestinal
sites
and
of
the
lymphatic
and
hematopoietic