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#175 - Dioxin Part 3: New Evidence That Dioxin Causes Human Cancers And Other Diseases, 03-Apr-1990

Two recent studies, published in 1988 and 1989, have indicated a
connection between exposure to dioxin and development of cancers in
humans. Earlier studies had shown little evidence linking human cancers
to dioxins, but these earlier studies have now been challenged by U.S.
government officials as fraudulent. (See RHWN #171.) One of the recent
studies also reveals a connection between dioxin exposure and a variety
of non-cancer health effects, including heart attacks (among men), and
digestive diseases, cirrhosis of the liver, gall bladder and biliary
tract diseases, and genitourinary diseases (among women).

Seveso, Italy

On July 10, 1976, an industrial disaster occurred at a chemical plant
operated by the pharmaceutical giant, Hoffman-La Roche, in the town of
Meda, Italy. A visible chemical cloud containing dioxin (2,3,7,8-TCDD
and other dioxins) spread over several square miles of populated
countryside; most heavily hit was the community of Seveso. More than
200,000 people aged 20 to 74 lived in towns near the accident. Nearly
31,000 people aged 20 to 74 lived in zones contaminated to some degree
by the accident and about 200 individuals had such high exposures that
they developed chloracne, an acne condition known to be caused by
exposure to dioxins.

A team of Italian physicians and researchers has been studying health
conditions, including death certificates, of 30,703 people aged 20 to
74 living in areas termed "exposed," comparing people's experience
there against a larger population of 167,391 individuals aged 20 to 74
living nearby in non-exposed areas. A recent report in the AMERICAN
JOURNAL OF EPIDEMIOLOGY [1] reveals several elevated disease rates
among the exposed group.

The report covers the decade 1976 to 1986, which is a short period in
which to find cancer occurrences. All cancers exhibit a "latency
period" (or delay period) between the time a cancer-causing exposure
occurs and a cancer actually develops; the latency period varies from 7
to 40 or 50 years. Thus a study of cancers occurring 10 years after an
exposure to cancer-causing chemicals could only reveal the earliest
evidence of cancers and should be understood to be preliminary in
nature.

The results of the study are reported for people living in three areas,
labeled zones A, B and R. Zone A is closest to the accident site and
zone R extends several miles distant; zone B is between the two. The
assumption is that people's exposure varied with distance from the
accident.

In zone A, women had elevated cancers of the gall bladder and biliary
tract. They also had elevated occurrences of circulatory diseases and
of chronic rheumatic heart disease. Men in zone A had elevated
occurrence of cerebrovascular disease (such as stroke). In zone B, men
had elevated melanomas (serious skin cancers) and cancers of the lining
of the chest cavity (pleura); women in zone B had elevated incidence of
soft tissue sarcomas. In zone R, men had elevated incidence of cancers
of the lining of the chest cavity (pleura), and they had increased
incidence of all blood diseases, and of cerebrovascular disease; women
in zone R had increased incidence of cancer of the uterus, as well as
hypertensive vascular disease.

The results reported above are averages for the entire decade. In the
case of cancers, which would only begin to occur after a latency
period, the timeperiod of interest is the second five years of the
decade, and, accordingly, the Italian researchers reported results for
each half of the decade.

During the second half of the decade: In zone A there were no elevated
cancer levels. In zone B, men showed elevated incidence of cancers of
the lung, cancers of the lining of the chest cavity (pleura), serious
skin cancers (melanoma), Hodgkin's disease (cancer of the lymph nodes),
and leukemia. In zone B, women showed increased incidence of soft
tissue sarcomas and of the thyroid gland. In zone R, men showed
elevated incidence of leukemia, and women showed elevated incidence of
cancer of the brain. It is perhaps relevant to note that two previous
studies have implicated brain cancer with exposure to dioxins in weed
killers. [2, 3]

This study of the people exposed to dioxin during the Seveso accident
does not prove that dioxin exposure caused the cancers or the other
serious ailments from which these people suffer in abnormally high
numbers (mainly diseases of the heart, blood, and arteries).
Nevertheless, this study confirms that it is definitely misleading and
untrue when anyone says there is "no evidence" of cancer or other
serious diseases among humans exposed to dioxins. (In addition, an
earlier U.S. government study has shown that Vietnam veterans exposed
to Agent Orange [a weed killer contaminated with dioxin] suffer from
elevated incidence of cancers, liver damage, cardiovascular
deterioration, and degeneration of the endocrine system. See RHWN #73.)

Sweden

Phenoxyacetic acids (for example, the weed killers known as 2,4,5-T and
2,4-D) are almost always contaminated with dioxins during manufacture.
During the late 1970s, Swedish researchers studied workers who had been
exposed to phenoxyacetic acids and found increased incidence of soft
tissue sarcomas (rare cancers of the connective tissues). [4, 5] During
the mid'80s, several additional studies confirmed the relationship
between soft tissue sarcomas and exposure to phenoxy herbicides, while
other studies failed to confirm such a relationship. Now a new study
has once again shown a three-fold increase in soft tissue sarcomas
among workers exposed to phenoxy herbicides. [6] This is the tenth
study that we know of showing a positive relationship between exposure
to phenoxy herbicides and soft tissue sarcomas. [7] Five studies have
failed to confirm such a relationship. [8]

How can one make sense out of conflicting reports, when 10 studies show
that certain chemicals cause cancer and 5 studies show that those same
chemicals do not cause cancer? How can the public know what policies
make sense to pursue?

In our experience, people who make money manufacturing, or using, such
chemicals prefer to argue that "we just don't know," and "until all the
facts are in, we should not make any changes." Unfortunately, all the
facts will never be in. People, including consumers buying phenoxy
herbicides at the lawn-care store and politicians making laws, will
always have to make decisions based on incomplete information.

From our viewpoint, the key question is this: Is it more important to
protect people and the environment from damage, or to protect chemicals
from regulation, control and outright bans?

--Peter Montague

=====

[1] Pier Alberto Bertazzi and others, "Ten-year Mortality Study of the
Population Involved in the Seveso Incident in 1976," AMERICAN JOURNAL
OF EPIDEMIOLOGY, Vol. 129 (1989), pgs. 1187-1200.."

[2] A. Bair and others, "Lung Cancer and Other Causes of Death Among
Licensed Pesticide Applicators," JOURNAL OF THE NATIONAL CANCER
INSTITUTE Vol. 71 (1983), pgs. 31-37.

[3] D. Coggon and others, "Mortality of Workers Exposed to 2-methyl-4-
chlorophenoxy-acetic acid." SCANDINAVIAN JOURNAL OF WORK, ENVIRONMENT
AND HEALTH Vol. 12 (1986), pgs. 448-454.

[4] Olav Axelson and others, "Herbicide Exposure and Cancer Mortality,"
SCANDINAVIAN JOURNAL OF WORK, ENVIRONMENT AND HEALTH Vol. 6 (1980),
pgs. 73-79.

[5] Lennart Hardell and others, "Malignant Lymphoma and Exposure to
Chemicals, Especially Organic Solvents, Chlorophenols, and Phenoxy
Acids: A Case-Control Study." BRITISH JOURNAL OF CANCER Vol. 43 (1981),
pgs. 169-176.

[6] Lennart Hardell and others, "The Association Between Soft Tissue
Sarcomas and Exposure to Phenoxyacetic Acids--A New Case-referent
Study," CANCER Vol. 62 (1988), pgs. 652-656.

[7] Nine of the studies are listed in footnotes 1 through 9 of the
Hardell study we cited in our footnote 6 (above), and the tenth study
is the Hardell study itself cited in our footnote 6 (above).

[8] The five studies are listed in footnotes 10 through 14 of the
Hardell study we cited in our footnote 6 (above).

Descriptor terms: seveso, italy; dioxin; gender; males; females;
cancer; gall bladder; gall bladder cancer; circulatory; heart disease;
herbicides; agent orange; phenoxyacetic; hodgkin's disease; lung
cancer; skin cancer; sarcomas; uterine cancer; leukemia; brain cancer;