=======================Electronic Edition========================
RACHEL’S HAZARDOUS WASTE NEWS #334
— April 22, 1993 —
News and resources for environmental justice.
——
Environmental Research Foundation
P.O. Box 5036, Annapolis, MD 21403
Fax (410) 263-8944; Internet: erf@igc.apc.org
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NEW STUDY LINKS DDT TO BREAST CANCER
Do trace residues of industrial chemicals harm humans?
A new study published yesterday in the JOURNAL OF THE NATIONAL
CANCER INSTITUTE reports that breast cancer in American women is
strongly associated with DDE (a form of DDT) in their blood.[1]
Breast cancer strikes 176,000 women in the U.S. each year, and
each year 46,000 die of it. DDE is a residue derived from the
well-known pesticide, DDT. DDT was banned in the U.S. in the
early 1970s but trace residues are still measurable nearly
everywhere in the environment. Furthermore, DDT is still
heavily used today in many locations outside the U.S.
The principal author of the new study, Dr. Mary Wolff at the Mt.
Sinai School of Medicine in New York, says, “[Our] findings
suggest that environmental chemical contamination with
organochlorine residues may be an important etiologic [causal]
factor in breast cancer. Given the world-wide dissemination of
organochlorine insecticides in the environment and the food
chain, the implications are far-reaching for public health
intervention worldwide.”
The study shows that women with high levels of DDE in their blood
have a four-times-greater risk of breast cancer than women with
low levels of DDE in the blood. (In this case, “high” means 20
billionths of a gram of DDE in each milliliter of blood and
“low” means 2 billionths of a gram in each milliliter of blood.
There are 28.3 grams in an ounce, and 4.7 milliliters in a
teaspoon.)
The study group was selected from 14,290 New York City women who
had attended a mammography (breast x-ray) clinic and had each
donated 30 milliliters of blood. Within the group of 14,290, 58
women who later developed breast cancer were selected for a
case-control study. The 58 “cases” were matched with 164
“controls,” women from the large group who did not have breast
cancer but who were matched to the “case” women in several key
respects (such as age, menopausal status, and so forth). All
their blood samples were analyzed for DDE and PCBs. DDE is
created when DDT is metabolized (processed by a living organism
that has eaten it). PCBs are industrial chemicals originally
used as insulators in electrical equipment. PCBs were banned in
the U.S. in 1976 but are still measurable in all parts of the
environment. (In the study, PCBs were also associated with
breast cancer but the association was not statistically
significant. There was one chance in 6 that the association was
due to random chance and statistical significance was defined as
one chance in 20, or less.)
For fifty years, the incidence of breast cancer in American women
has risen at a steady 1 percent per year.[2] In 1940, an
American woman’s lifetime risk of getting breast cancer was one
in 16. Today it is one in 8. (See Table 1, which shows the
risk of breast cancer in the U.S. today for women at various
ages.) However, death from breast cancer has remained steady
throughout the past 20 years because of life-saving, though
brutal, treatment methods (chemotherapy, radiation therapy, and
surgery).
No one doubts that something in the environment is responsible
for the rising incidence of breast cancer in the U.S. Japanese
women have only one-fifth as much breast cancer as American
women; but when Japanese women move to the U.S., they are
stricken with breast cancer at U.S. rates.
Since the 1960s, medical specialists have been trying to track
down the causes of breast cancer. Throughout the 1980s, most
scientists believed that a high-fat diet caused breast cancer. A
study of diet and breast cancer in 120,000 women has now
discredited this theory and it has been abandoned.[2]
Researchers are now focused on the female hormones estrogen and
progesterone which, they suspect, may play a large role in
breast cancer.
It has been known since the early 1970s that breast cancer is
somehow related to estrogen. Beginning at menarche (the onset
of menstruation) and continuing until menopause, a women
experiences a sharply rising and falling exposure, first to
estrogen and then to progesterone, in a repeating 4-week
ovulation cycle.
Late menarche and early menopause (both of which reduce a
woman’s lifetime exposure to estrogen) are both associated with
reduced breast cancer risk. In addition, women who have their
ovaries removed early in life and are therefore exposed to much
less estrogen that other women, rarely have breast cancer.
Furthermore, women who have “estrogen replacement therapy” (i.e.,
take estrogen pills) have a 40 percent increased risk of breast
cancer, and women who use birth control pills have a 50 percent
increased risk of breast cancer. These clues all relate
estrogen to breast cancer.
But the EXACT relationship is not understood.
In recent years, menarche in American women has been occurring
at earlier and earlier ages. (Chinese women reach menarche at
age 17; today U.S. women reach menarche at 12.8 years, on
average, but 200 years ago North American women reached menarche
at age 17.) The declining age of menarche in U.S. women
increases their lifetime exposure to estrogen, which possibly
increases their risk of breast cancer.
What is causing the declining age of menarche? Some scientists
say simply, improved nutrition. Others say it may be caused by
industrial chemicals in our food that mimic hormones and
interfere with the internal mechanisms that regulate our
bodies. DDT, DDE, PCBs and dioxin are examples of chemicals now
known to mimic hormones and disrupt the endocrine system of
fish, birds and mammals, including humans.[3]
Dr. Patricia Whitten at Emory University in Atlanta, Ga., has
examined historical records extending back 200 years in several
countries. Dr. Whitten’s concludes that improved nutrition
cannot account for all the changes in human reproduction that
are observable in the historical record. She believes that
hormone-mimicking industrial chemicals in the environment
provide a more satisfactory explanation.[4]
The debate over menarche has real consequences in the kinds of
research that scientists are doing. Scientists who believe
hormone-mimicking industrial chemicals may play an important
role are doing the kinds of studies reported today in the
JOURNAL OF THE NATIONAL CANCER INSTITUTE, examining
hormone-mimicking chemicals like DDT in relation to breast
cancer.
On the other hand, those who believe improved nutrition provide
sufficient explanation for the change in menarche tend to ignore
external influences, such as environmental chemicals. Malcolm
Pike at University of Southern California (USC) School of
Medicine has emerged as a leader of this school of thought. Pike
argues as follows: nutrition is the cause of reduced age of
menarche; nutrition is unlikely to worsen, so we’re stuck with
reduced age of menarche and therefore with increased exposure to
estrogen. Pike is experimenting with a technical fix, giving
women additional chemicals (pharmaceuticals) to block their
natural production of estrogen, then giving them controlled
doses of estrogen, to maintain their chemical balance
artificially. SCIENCE magazine reported January 29, 1993 that,
“To the extent it’s possible to see a trend emerging in the
1990s, this anti-estrogen strategy appears to be a leading
contender.” Dr. Walter Willett at Harvard University’s School
of Public Health is in Pike’s camp. He says, “In the end, I
think we’re going to have to go with a pharmacological fix.”
SCIENCE comments “There may be some reluctance to support such
experiments because people feel they are ‘unnatural.’” But, says
Willett, “our whole lifestyle is unnatural.”
Dr. Wolff’s new study does not definitively prove that chemical
residues cause breast cancer. The number of “cases” is small.
Additional research will be needed. Nevertheless, an editorial
in the JOURNAL OF THE NATIONAL CANCER INSTITUTE yesterday said,
“Because the findings of Wolff [and associates] may have
extraordinary global implications for the prevention of breast
cancer, their study should serve as a wake-up call for further
urgent research.”[5]
–Peter Montague, Ph.D.
=================================================================
Table 1
A Woman’s Risk of Developing Breast Cancer Today in the U.S.
| By age 25: | one in 19,608 |
|---|---|
| By age 30: | one in 2525 |
| By age 35: | one in 622 |
| By age 40: | one in 217 |
| By age 45: | one in 93 |
| By age 50: | one in 50 |
| By age 55: | one in 33 |
| By age 60: | one in 24 |
| By age 65: | one in 17 |
| By age 70: | one in 14 |
| By age 75: | one in 11 |
| By age 80: | one in 10 |
| By age 85: | one in 9 |
| Ever: | one in 8 |
Source: See footnote 2.
=================================================================
Descriptor terms: pesticides; ddt; dde pcbs; breast cancer;
morbidity; mortality; mary wolff; mt. sinai school of medicine;
new york; women; hormones; estrogen; endocrine disruptors;
menarche; menopause; estrogen replacement therapy; birth control
pill; the pill; patricia whitten;