Developmental Window of SusceptibilityBreast tissue undergoing rapid growth may be especially susceptible to environmental influences. This idea is supported by animal studies, and by epidemiological studies that find an association between early exposure to radiation and subsequent cancer. “Development is the most susceptible window that actually affects us long term,” Birnbaum said. Each of the four centers coordinates lab research, population studies and community outreach. The centers include patient advocates as partners in the planning and implementation of research. Birnbaum noted that the centers, now in their sixth year, are a new model for community participation in major government-sponsored research projects. Panelist Janice Barlow, head of the Marin-based advocacy group Zero Breast Cancer, emphasized that advocacy groups have been the driving force for the research. “The Breast Cancer and the Environment Research Centers came out of strong advocacy groups in the Bay Area and throughout the country that wanted a focus on environmental factors in the development and initiation of breast cancer.” Barlow encouraged participation in such collaborative studies. “It really does change the direction that the research is taking, making it more relevant to the community,” she said. BABCERC includes many institutional collaborators and community partners.
Genes, Hormones and EnvironmentBirnbaum, a toxicologist, has been an author on more than 700 research studies to evaluate possible links between exposure to environmental chemicals and human health impacts. In addition to serving as director of NIEHS, Birnbaum also directs the National Toxicology Program. Genetic alterations play a large role in cancer, and having a mother or sister with breast cancer increases a woman’s risk for one day receiving the same diagnosis. But the influence of the environment can alter the actions of genes, Birnbaum said: “Even identical twins are not identical. They may have the same sequence of bases in their DNA, but the environment affects how that DNA is actually expressed.” Breast cancer also is driven by hormones, and in animals many chemicals of interest to advocates and researchers disrupt normal feedback control of hormone signaling. Birnbaum, along with NIEHS administrators Gwen Collman, PhD, acting director of extramural research, and Rupali Das, MD, MPH, chief of the exposure assessment section, highlighted additional agency-sponsored breast cancer research initiatives aimed at detecting environmental influences on breast cancer. The largest, called the Sister Study, includes 50,000 healthy women, ages 34 to 74, who have sisters that have previously been diagnosed with breast cancer.
Biomonitoring, Body Burdens and Flame RetardantsBiomonitoring -- the quantification of chemicals in blood and urine -- has gained popularity as a research tool over the past decade. BABCERC researchers are measuring levels of estrogen-disrupting chemicals such at the phthalates and bisphenol A, as well as exposure to metals. Biomonitoring also is underway at the state and federal levels. Another group of chemicals, used as flame retardants, also is arousing concern in California and in the rest of the country. The European Union already has banned several flame retardants. “California unfortunately is a bit of a natural experiment for a group of chemicals that are unintended consequences of our early anti-flammability laws,” said panelist Peggy Reynolds, a senior research scientist at the Northern California Cancer Center. Flame retardants “are in the chairs you’re sitting in, the computers you’re working with – all around us.…California does seem to have some of the highest body burdens in the world for a number of these chemicals.” Birnbaum noted that these chemicals have not yet been evaluated for cancer risk. However, studies within the past two years indicate that they do indeed merit concern, she said. Research reveals that a higher body burden of flame retardants in pregnant women is associated with an increased incidence of undescended testes in male children. Studies of adults and newborns find an association with lowered male hormone levels and abnormal thyroid hormone levels. Jeanne Rizzo, president and CEO of the Breast Cancer Fund, was applauded when she argued that the ongoing use of suspect chemicals such as flame retardants is unacceptable: “If we have a known carcinogen, a known reproductive toxin, or a known endocrine disrupter, and we have animal studies that tell us that these are dangerous chemicals, then as an advocacy group we are going to work to reduce our exposure to those chemicals, and flip the paradigm -- so that it’s up to the purveyor of those chemicals to prove that they’re safe, rather than that we have to prove they’re harmful by getting sick.”
Policy QuestionsBirnbaum, whose tenure as the new leader of the NIEHS began the day President Barack Obama was inaugurated, was questioned about her views on regulating potential environmental health risks. She described as “ineffective,” the federal law, on the books since 1978, through which the Federal Environmental Protection Agency regulates chemicals in commerce. Chemicals already in use when the law passed are exempt from testing. Chemicals now in widespread use as flame retardants already were in use before the act passed, but only in small quantities for other industrial purposes. Birnbaum is scheduled to appear before the US Senate Committee on Environment and Public Works to discuss revisions of the law. “We have this report card of what we have in our bodies,” she said. “We don’t know what in means in many cases, but in some cases we do.” Without specifying chemicals, Birnbaum said, “We know that for some chemicals the levels that are in our bodies are similar to the levels that in animal studies have been shown to cause problems, and I think that should be an indication for some action. “You act in the presence of evidence that there could be harm, without requiring certainty that there is harm. It doesn’t mean that you act in the absence of any information at all.” It’s still early days for research discoveries. “When you start to look, you start to find things,” Birnbaum said.
Related LinksEarly Puberty and Early Exposure to Breast Cancer Risks: A Conversation with Robert Hiatt
UCSF Science Café: Breast Cancer and the Environment Research Centers