Common chemicals are linked to breast cancer
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Common chemicals are linked to breast cancer
Of the 216 compounds, many in the air, food or everyday items.
By Marla Cone
Times Staff Writer
May 14, 2007
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 disease.
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 exposures.
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 reports.
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 reports.
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 risk.
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 animals."
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 professor.
But Hunt and Soto urged society not to wait for scientific proof to
reduce exposure to the chemicals.
"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
DNA.
Breast cancer is probably triggered by an interaction of multiple
environmental and genetic factors.
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 http://www.silentspring.org/sciencereview .
http://www.latimes.com/news/nationworld/nation/la-na-cancer14may14,1,6867764.story?track=rss
Common chemicals are linked to breast cancer
Of the 216 compounds, many in the air, food or everyday items.
By Marla Cone
Times Staff Writer
May 14, 2007
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 disease.
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 exposures.
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 reports.
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 reports.
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 risk.
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 animals."
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 professor.
But Hunt and Soto urged society not to wait for scientific proof to
reduce exposure to the chemicals.
"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
DNA.
Breast cancer is probably triggered by an interaction of multiple
environmental and genetic factors.
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 http://www.silentspring.org/sciencereview .