Breast cancer in lab mice brought on by common chemical in study

• A chemical found in cleaning materials, textiles, plastics, paper and some personal-care products can trigger breast cancer, at least in lab animals, a new study has found.
• Since the early 1990s, experts have known that the chemical, called 4-nonylphenol, binds to estrogen receptors, said senior study author William Baldwin, an assistant professor of biological sciences at the University of Texas at El Paso.
• In the liver, 4-nonylphenol stimulates an enzyme system that then boosts production of estriol, a hormone associated with breast cancer.
• "There have been a couple of studies in animals that showed a proliferation of mammary tissue when exposed to NP-4," Baldwin said.
• In the study, Baldwin and his team compared the effects of giving differing doses of the chemical and estrogen to mice.
• When they followed mice genetically engineered to readily develop breast cancer over 32 weeks, many of those given 4-NP developed breast cancer while those given equivalent doses of estrogen did not.
• "In 10 or 15 years, we will figure out if environmental estrogens are a cause or part of the cause for breast cancer," he said.
• Baldwin and other experts estimate that established risk factors such as aging, early onset of periods, late menopause, delayed childbearing and genetics explain only about 25 percent to 50 percent of breast cancers, and that environmental exposure plays a big role.
• Brenda Salgado is program manager for Breast Cancer Action, a San Francisco-based organization that lobbies for environmental reforms, such as seeking legislation to label all carcinogens in cosmetics.
• She said that, while it's premature to give women advice based on just this study, they "should be conscious of chemicals that have an estrogenic effect and limit exposure to those chemicals."