Articles Available for Reprint

The following occasional articles are available for reprint at no cost and without direct permission from Silent Spring Institute. We do require, though, that you credit Silent Spring Institute and let us know when you use an article.

A case for breast cancer prevention
The legacy of Rachel Carson
Chemicals and cancer
Pollution hits home
Clues you can use


A case for breast cancer prevention

Every October, we’re awash in a sea of pink ribbons. Information about breast cancer risk factors swirls through the media, but when it comes to environmental factors, it’s often radio silence or claims that there’s “no evidence.” If there’s no evidence, then we don’t need to take action, right? Maybe it’s time to reconsider how we think about public health evidence.

“How do we know the gunshot killed the victim?” asked Julia Brody, Executive Director of Silent Spring Institute, during her testimony to the President’s Cancer Panel. “The gun was raised and fired, the bullet entered a vital organ, and the victim fell to the ground.” But how do we know environmental factors contribute to breast cancer? In this case, it’s much harder to establish a clear cause and effect relationship.

Each year, the President’s Cancer Panel—a watchdog group of advisors charged with monitoring the National Cancer Program—holds a series of meetings to gather input from experts and the public on a particular theme. While in past meetings the panel has focused on topics such as lifestyle and treatment, this year they are focusing, for the first time ever, on environmental factors. The panel will present a report with its recommendations to President Obama later this year.

At the panel’s meeting on Air Pollution and Water Contamination, Brody advocated a new strategy for environmental health sleuthing. Taking the traditional “innocent until proven guilty” approach—which requires waiting for definitive proof that a given chemical causes breast cancer before taking action—hasn’t been working. This is because it can take many years after an exposure for breast cancer to develop, women are exposed to a toxic soup of chemicals, and it’s difficult to untangle the many interwoven genetic and environmental factors that can contribute to the disease.

With medical research, we can dispel some of this ambiguity by using clinical trials to test, for example, the safety of a given drug. But we can’t apply this model to study the effects of pollutants on women’s health because it would be unethical to test a toxic chemical on a group of women and wait to see if they get sick. So what, then, are we to do?

We don’t have to throw up our hands in the face of this challenge. Instead, we can work to build the case for a “better safe than sorry” approach that would rely on animal and cell studies that illustrate how chemicals can contribute to breast cancer, and studies showing humans are exposed to those same chemicals. Taken together, this evidence would create the foundation for preventive action to reduce our exposures to harmful chemicals.

“We see substantial evidence of links between environmental pollutants and breast cancer, enormous knowledge gaps that we can fill immediately, and opportunities for precautionary action,” said Brody. “If we take steps to protect ourselves and our children from chemicals that cause cancer, we will also see benefits for numerous other health endpoints, including diabetes, obesity, neurological disease, and infertility.”

Read the full text of Brody’s testimony.

Sarah Dunagan, MA, is a Staff Scientist at Silent Spring Institute in Newton, Massachusetts. Reprinted courtesy of Silent Spring Institute.

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The legacy of Rachel Carson

A courageous and outspoken woman, an extraordinary scientist and naturalist, and a writer with a gift for lyricism about the mundane doings of insects, shellfish, and birds, Rachel Carson died of breast cancer just two years after the 1962 publication of her book Silent Spring touched off the modern environmental movement.

When she testified about the dangers of DDT just before her death, Carson wore a wig to hide her treatment as she forthrightly told Congress, “I hope this committee will give attention to the right of the citizen to be secure in his own home against the intrusion of poisons applied by other persons. This should be one of the basic human rights.” Since Carson’s death, many have wondered whether a connection exists between the environmental toxics that inspired her work and the disease that killed her.

As a new generation of remarkable women brought breast cancer out of hiding with growing activism since the 1990s, questions about breast cancer and the environment became ever more compelling. Women with breast cancer have stood together at rallies, walks, and swims and in the halls of Congress; and by becoming visible in our communities, they have transformed that gnawing question, “Why did I get breast cancer?” into “Why do we have rising breast cancer rates worldwide? What can we learn to bring risk back down and truly end the epidemic?”

When we see that a woman’s lifetime risk of breast cancer rose from one in fourteen in Carson’s day to one in eight today, we know that prevention is a realistic goal. Faced with statistics like these, many have been frustrated, though, that the breast cancer research establishment is focused so heavily on treatment with little investment in prevention.

So in 1993, when leaders in the Massachusetts Breast Cancer Coalition learned that breast cancer incidence was higher on Cape Cod than in the rest of the state, they decided that breast cancer activists across the country needed a laboratory of their own to find out why. They founded Silent Spring Institute the next year as a partnership of scientists and activists with a mission to study the links between the environment and women’s health, beginning with breast cancer.

Many of these women were inspired to become breast cancer activists through their own struggle with the disease. As it was with Carson, prevention comes too late for them, but that doesn’t blunt their passion for seeking solutions. Over and over I hear them saying, “I’m working for my daughters, for my granddaughters.” In their quest to understand the truth about the imbalances we’re creating in nature, they consider themselves to be Rachel Carson’s daughters.

Julia Brody, PhD, is the executive director of Silent Spring Institute in Newton, Massachusetts. Reprinted courtesy of Silent Spring Institute.

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Chemicals and cancer

The statistics on worldwide increases in breast cancer risk are grim. Rapidly increasing risk in the developing world, where mammography is still rare, tells us we are seeing more disease, not just more diagnosis. The increase cannot be due to inherited genes either, because inherited genes can’t change over just a couple of generations.

Studies that show increased risk for women who move from low-incidence regions to high-incidence countries, like the United States, point to something about the way we live in industrial societies. Thus far, scientists have been able to explain less than half of breast cancer risk with all the identified risk factors. That means that additional, unknown causes must be at work. If we can find out why incidence is increasing, we can learn to prevent future disease.

Where should we look for clues to prevention? Synthetic chemicals that poured into the marketplace after World War II are one promising direction, because laboratory studies point to three mechanisms that could link various chemicals to breast cancer: chemical carcinogens that can damage DNA; tumor promoters that can make cells grow; and developmental toxicants that can leave the mammary gland more vulnerable to carcinogens.

The U.S. National Toxicology Program has identified 42 chemicals as breast carcinogens in laboratory animals, and about 100 have been identified internationally. Many are common. For example, we are exposed to carcinogenic polycyclic aromatic hydrocarbons (PAHs) in grilled and smoked food, tobacco smoke, and air pollution from auto exhaust, power plants, and other fossil fuel-burning processes. Until recently, ethylene oxide was commonly used in hospitals and medical facilities to sterilize instruments, though the U.S. Occupational Safety and Health Administration set limits to reduce exposures. Other mammary carcinogens can be found in certain furniture finishes, dyes, and solvents.

Once a cancer begins, other chemicals, called tumor promoters, may stimulate growth. We have known for years that natural estrogens and pharmaceutical estrogens, such as hormone replacement therapy, affect breast cancer risk. We now know that synthetic chemicals can also make human breast cancer cells proliferate in laboratory studies. Drs. Ana Soto and Carlos Sonnenschein at Tufts University pioneered the study of estrogen mimics in breast cancer cells after they found a chemical that was accidentally leaching from plastic tubing in their experiments was causing cell growth. Estrogen mimics are part of a larger group of chemicals known as endocrine disrupting compounds (EDCs) because they affect hormones. EDCs are found in some plastics, pesticides, detergents, and cosmetics, among other sources.

Most recently, scientists at the U.S. Environmental Protection Agency discovered a third way that chemicals may increase breast cancer risk. When they dosed laboratory animals with the pesticide atrazine during certain weeks of pregnancy, the offspring never developed fully mature mammary glands, leaving the daughters more vulnerable throughout life to carcinogenesis.

Making the link from strong laboratory evidence to epidemiologic studies in women remains a challenge, because it’s so difficult to measure exposure to a complex mixture of pollutants over a lifetime. But the laboratory studies can help us target precautionary public health policies to reduce exposure, and they point us to urgent areas for breast cancer studies.

Julia Brody, PhD, is the executive director of Silent Spring Institute in Newton, Massachusetts. Reprinted courtesy of Silent Spring Institute.

For more scientific detail and a list of mammary carcinogens and EDCs, read “Environmental Pollutants and Breast Cancer” from Environmental Health Perspectives.

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Pollution hits home

In 1987, Dr. Ana Soto at Tufts University faced a perplexing problem. She was studying how exposure to estradiol—a natural estrogen—makes estrogen-sensitive human breast cancer cells grow. But, unexpectedly, the unexposed control cells in her lab began to proliferate. It took years to figure out that new plastic test tubes in her laboratory were to blame. The tubes were leaching nonylphenol, a synthetic chemical found in many common products, such as detergents, plastics, and pesticides.

With this discovery, Dr. Soto began a new area of research that has led her laboratory and others to identify more than 150 chemicals that mimic estrogen, block androgen, or otherwise affect hormones. These chemicals are known as endocrine disrupting compounds (EDCs). They are found in building materials, furniture, and everyday products—detergents, pesticides, plastics, cosmetics—and in air and water pollution.

Given that natural estrogen and pharmaceutical estrogens, such as hormone replacement therapy, increase breast cancer risk, it makes sense to target estrogen mimics and other EDCs in breast cancer research. If we find links between these chemicals and breast cancer, we will be a big step closer to breast cancer prevention.

To understand the links between chemicals and breast cancer, we need to first measure and understand how women are exposed. Because many of the EDCs are in consumer products and because we all spend a great deal of time at home, Silent Spring Institute decided to tackle EDCs in a study of exposures in homes.

Silent Spring researchers tested for 89 EDCs in air and dust in 120 homes on Cape Cod, where the Institute has been studying possible environmental links to breast cancer since 1994. Results of the Household Exposure Study were published in the journal Environmental Science & Technology, which called the study “the most comprehensive assessment to date” of pollutants in homes. For 30 of the chemicals tested, Silent Spring’s measurements were the first ever reported from indoor environments.

The researchers found 67 target compounds in all, with an average of about 20 per home. That’s a reminder that when we think about effects of chemicals on health, we have to take into account multiple exposures rather than the one-at-a-time approach that is currently used for chemicals regulation.

The most abundant pollutants uncovered in the Household Exposure Study were phthalates (from plastics and personal care products, such as nail polish and hairspray) and certain phenols from disinfectants, detergents, and adhesives, such as those found in furnishings. Phthalates were found in every home. These chemicals are associated with androgen-blocking effects in males, including lowered sperm count and certain hormonal birth defects; their effects on girls and women have not been investigated much yet. Many breast cancer activists have joined the effort to remove phthalates from cosmetics, as the Europeans are doing, and more than a hundred cosmetics manufacturers have agreed. The researchers also found the flame-retardant polybrominated diphenyl ethers, or PBDEs, at ten times the levels reported in Europe, where these chemicals are not used as much. These chemicals have been shown to affect hormone systems and thyroid hormones, to cause reproductive harm, and to affect learning and behavior in animal studies.

The study also showed that chemicals break down very slowly indoors. The scientists found DDT, which has been banned in the United States since 1972, in about two-thirds of the homes. As toxicologist Ruthann Rudel says, “Think about what your furniture would look like if you left it out on the street for 30 years. Now think about it in your living room. Protected from sun, rain, and wind, the materials stay pretty much intact.”

One of the key lessons from the Household Exposure Study is that we must be more careful about testing chemicals before we put them into use, because banning them later won’t get them out of our homes.

Julia Brody, PhD, is the executive director of Silent Spring Institute in Newton, Massachusetts. Reprinted courtesy of Silent Spring Institute.

For more scientific detail, visit Our Research.

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Clues you can use

Follow these ten strategies for reducing your personal exposure to suspect chemicals that are found in everyday products:

1. Use only glass and ceramic containers in the microwave. Some plastic containers contain chemicals that mimic or disrupt hormones. These chemicals can leach into food when they are heated.

2. Use dry cleaning services that do not use perchloroethylene (PERC) or request “wet cleaning.” Solvents such as PERC have been linked to various cancers. If you must use traditional dry cleaning with PERC, remove the plastic bags in an open space and air out your clothes before hanging them in a closet.

3. Read the labels of products, avoiding phthalates and fragrance. Phthalates are endocrine-disrupting compounds that have been associated with cancer, impaired fertility, and male birth defects. Phthalates are often an ingredient in fragrance, and they are found in hundreds of products, such as shampoos, lotions, perfume, cosmetics, vinyl, and plastics, including toys. Look for labels that say “phthalate-free.”

4. When grilling foods, minimize char by reducing the heat level and using marinades. Char contains PAHs, or polycyclic aromatic hydrocarbons, which are known to cause mammary tumors in animals. In the Long Island Breast Cancer Study, women who had more DNA damage from PAHs had a higher risk of breast cancer.

5. Purchase organic foods. Buying organic reduces your family’s exposure to pesticides. Many of these chemicals act as endocrine disruptors and are known to affect brain development and neurological function in humans.

6. Monitor what goes down the drain in your home. Help protect your indoor air and your community’s water supply by using minimal amounts of the least toxic cleaning products and pesticides. Never put cleaning solvents, pesticides, paint thinners, automobile oil, or gas down a drain.

7. Choose vacuum cleaners wisely. Carpets can harbor pesticides, flame retardants, other chemicals, and allergens such as mold. Cleaners with a strong suction, a brush on/off switch, and a multilayered bag for dust collection are the best at preventing the recycling of dust.

8. Look for furnishings and electronic equipment without PBDEs. PBDEs (polybrominated diphenyl ethers)—endocrine disruptors that affect thyroid hormones—are commercially produced flame retardants often added to polyurethane foam, various plastics, and electronics equipment. When possible, choose carpet pads, bedding, cushions, and upholstered furniture made from natural fibers, including wool, cotton, and hemp.

9. Adopt organic practices for lawn care and gardening. Children and pets that play on lawns are exposed to pesticides and herbicides. These chemicals are tracked into homes, and they can leach into waterways and drinking water wells.

10. Encourage your town to use natural, non-toxic solvents in public buildings, especially schools, and to follow organic practices in the care of green spaces. Using safer cleaners and eliminating pesticides on a town-wide basis helps reduce exposure to compounds that mimic estrogen or otherwise disrupt hormones.

Reprinted courtesy of Silent Spring Institute.

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