Times, Marla Cone
Of the 216 compounds, many in
the air, food or everyday items.
More than 200 chemicals — many found in urban air and
everyday consumer products — cause breast cancer in animal
tests, according to a compilation of scientific reports
More than 200 chemicals — many
found in urban air and everyday consumer products — cause
breast cancer in animal tests, according to a compilation of
scientific reports published today.
Writing in a publication of the American Cancer Society,
researchers concluded that reducing exposure to the
compounds could prevent many women from developing the
The research team from five institutions analyzed a growing
body of evidence linking environmental contaminants to
breast cancer, the leading killer of U.S. women in their
late 30s to early 50s.
Experts say that family history and genes are responsible
for a small percentage of breast cancer cases but that
environmental or lifestyle factors such as diet are probably
involved in the vast majority.
"Overall, exposure to mammary gland carcinogens is
widespread," the researchers wrote in a special supplement
to the journal Cancer. "These compounds are widely detected
in human tissues and in environments, such as homes, where
women spend time."
The scientists said data were too incomplete to estimate how
many breast cancer cases might be linked to chemical
But because the disease is so common and the chemicals so
widespread, "the public health impacts of reducing exposures
would be profound even if the true relative risks are
modest," they wrote. "If even a small percentage is due to
preventable environmental factors, modifying these factors
would spare thousands of women."
The three reports and a commentary were compiled by
researchers from the Silent Spring Institute, a women's
environmental health organization in Newton, Mass.;
Harvard's Medical School and School of Public Health in
Boston; the Roswell Park Cancer Institute in Buffalo, N.Y.;
and USC's Keck School of Medicine. Silent Spring Institute
Executive Director Julia Brody led the team.
In response to the findings, Susan G. Komen for the Cure, a
breast cancer prevention group that funded the work, pledged
an additional $5 million for developing research tools to
root out environmental causes.
Reviewing hundreds of existing studies and databases, the
team produced what it called "the most comprehensive
compilation to date of chemicals identified as mammary
carcinogens." No new chemical testing was conducted for the
The researchers named 216 chemicals that induce breast
tumors in animals. Of those, people are highly exposed to
97, including industrial solvents, pesticides, dyes,
gasoline and diesel exhaust compounds, cosmetics
ingredients, hormones, pharmaceuticals, radiation, and a
chemical in chlorinated drinking water.
"Almost all of the chemicals were mutagenic, and most caused
tumors in multiple organs and species; these characteristics
are generally thought to indicate likely carcinogenicity in
humans, even at lower exposure levels," they reported.
For many of the compounds, the federal government has not
used animal breast cancer data when conducting human risk
assessments, which are the first step toward regulating
chemicals or in setting occupational standards to protect
workers. Companies are not required to screen women who work
with the chemicals for breast cancer.
"Regulators have not paid much attention to potential
mammary carcinogens," the researchers wrote.
Toxicologists say that other mammals, such as rats and mice,
often develop the same tumors as humans do, and that animal
tests are efficient means of testing the effects of
chemicals. Environmental regulators, however, often want
conclusive human data before taking action.
Animal studies generally use high doses of a substance to
simulate a lifetime of exposure, and then the results are
extrapolated to the lower levels that people are exposed to.
Ana Soto, a Tufts University professor of cell biology who
specializes in cellular origins of cancer and effects of
hormone-disrupting contaminants, said there probably was a
link between breast cancer and exposures to chemicals in the
environment, particularly early in life.
"I cannot say I'm convinced, but what I can say is that it's
a very likely, very plausible hypothesis," said Soto, who
did not participate in the new research. "More and more,
cancer looks like an environmental disease."
Twenty-nine of the chemicals are produced in volumes
exceeding 1 million pounds annually in the United States.
Seventy-three are present in consumer products or are food
contaminants — 1,4-dioxane in shampoos, for example, or
acrylamide in French fries. Thirty-five are common air
pollutants, 25 are in workplaces where at least 5,000 women
are employed, and 10 are food additives, according to the
There are probably many more than 216, the
research team said, because only about 1,000 of
the 80,000 chemicals registered for use in the
United States have been tested on animals to see
whether they induce cancerous tumors or mutate
DNA. Such tests cost $2 million each.
Because epidemiological studies are difficult to
conduct and full of uncertainties, human data
are "still relatively sparse," the researchers
wrote. Only 152 studies worldwide have examined
whether women exposed to contaminants are more
likely to have breast cancer — compared with
nearly 1,500 that have explored the links
between diet and the disease — and most of the
216 carcinogens were not included.
"Despite this large remaining gap, research in
the last five years has strengthened the human
evidence that environmental pollutants play a
role in breast cancer risk," the researchers
wrote. They said the existing studies suggested
"substantial public health impact."
Human evidence is particularly strong for PCBs,
or polychlorinated biphenyls — compounds widely
used in the 1940s to late 1970s that still
contaminate fish and other foods — and for
polycyclic aromatic hydrocarbons, or PAHs, found
in diesel and gasoline exhaust.
Solvents in dry cleaning, aircraft maintenance
and other jobs also may increase breast cancer
Some of the chemicals named as breast
carcinogens already are regulated to protect
public health, but some, particularly those in
consumer products, are not.
The scientists conducted the review hoping to
lay the groundwork for new human studies, as
well as to persuade regulators to use existing
animal data to strengthen regulations and
require more testing of chemicals.
"Animal models are the primary means of
understanding and anticipating effects of
chemicals in humans," they wrote. "All known
human carcinogens … are also carcinogenic in
Emerging evidence suggests that the roots of
breast cancer are in infancy or the womb. More
animal and human research should focus on such
early exposure, said Patricia Hunt, a Washington
State University School of Molecular Biosciences
But Hunt and Soto urged society not to wait for
scientific proof to reduce exposure to the
"When you look at their list of chemicals, we
are exposed to all of it," Soto said. "We know
humans are exposed to mixtures, and studying
mixtures is very difficult. We will never have
the whole picture, and it will take many, many
years to collect epidemiological evidence, so we
should take some preventive measures now."
Although virtually all women are exposed to the
chemicals, some may be more susceptible because
of differing metabolism or ability to repair
Breast cancer is probably triggered by an
interaction of multiple environmental and
Experts have long suspected diet plays a role.
But the new research found "no association that
is consistent, strong and statistically
significant" for any particular foods raising or
reducing breast cancer risk. There is
substantial evidence, however, that regularly
consuming alcohol, being obese and being
sedentary increase risk.
About 178,000 new cases will be diagnosed this
year in the United States.
The reports are at
Researchers name 216 chemicals that cause breast
cancer in animal tests. Here are some of the
Detergents, shampoos, soaps,
cocoamide DEA, TEA, SLS, SLES
Common air pollutant; found in vehicle
foods, cosmetic products
Common air pollutant; found in vehicle
exhaust, cosmetic products
in manufacture of Teflon
in manufacture of plastics; found in
carpets, adhesives, hobby supplies and
other consumer products
almost exclusively by the plastics
industry to make vinyl-cosmetics
Industrial solvent; also found in some
consumer products such as paint removers
in foam cushions, furnishings, bedding,
in furniture polish, fabric cleaners,
wood sealants and many other consumer
Diesel and gasoline exhaust
Electrical transformers; banned but
still in environment
Widely used herbicide, particularly for
Source: Silent Spring Institute
Products without harmful chemicals or carcinogens