reducing or eliminating exposures received by groups of people). The next section discusses ways that the study of these factors could lead to approaches for preventing breast cancer. 2.3 Preventing Breast Cancer Evidence suggests that breast cancer has the potential to be prevented. In addition to the fact that the majority of cases occur in women with no family history of the disease, the fact that breast cancer The environment includes lifestyle and behavioral factors, chemical and physical agents, and social and cultural influences. In June 2009, the Secretary of the HHS, Kathleen Sebelius, delegated the authority for implementing IBCERCC to the NIH. The Director of the NIH delegated this task specifically to the NIEHS in July 2009. The Charter for the Committee was signed by the Director of NIEHS, Dr. Linda Birnbaum, on September 3, 2009 (see Appendix 1). NIEHS and NCI staff organized the Committee under the rules for NIH Federal Advisory Committees.19 Formal meetings of the full Committee took place on September 30 to October 1, 2010, in Washington, DC; on May 12 to 13, 2011, September 26 to 27, 2011, and January 23 to 24, 2012, at NIEHS in Research Triangle Park, NC; and on May 9, 2012, in Arlington, VA. In addition to formal meetings, members used email, teleconferences, and informal meetings to jointly accomplish the activities required of the Committee. To complete the work, the Committee worked principally through three subcommittees on the state of the science; research process; and translation, dissemination, and policy implications. Each subcommittee included clinicians, scientists, advocates, and community members, and all Committee members interacted extensively during the preparation of this report. At the initial meeting of the Committee, Dr. Birnbaum asked the IBCERCC “to address the legislative mandate boldly and provocatively, consider the totality of the issues before prioritizing them, and develop a usable product that will guide the future of federally conducted and supported research on breast cancer and the environment.” 2.2 Defining the Environment For the purposes of this report, the environment includes all of the surroundings of and influences on The report has been written jointly by scientists, government agency representatives, clinicians, advocates, and consumer representatives. 2-5 Breast Cancer and the Environment: Prioritizing Prevention 2 2.4 Concepts Considered Throughout the Report The Committee considered the following key concepts in developing this report: • Leverage scientific advances across a wide range of disciplines and look for opportunities for collaboration to transform breast cancer science. The Committee reviewed scientific research and training programs as well as the full spectrum of methods and disciplines that pertain to breast cancer and environment research. The Committee found gaps and opportunities in all areas, and the report is comprehensive in presenting these gaps/ opportunities for consideration. • Recognize that the timing of exposure to environmental and lifestyle risk factors matters. The molecular and cellular changes that lead to breast cancer can occur early in life and endure across the life span.27 Susceptibility to the initiation of breast cancer changes begins with the developmental stage of the mammary gland (this report uses this term instead of “breast” when referring to laboratory animals) and continues through the many stages of mammary gland/breast development across the life span.27 This Committee examined exposures throughout life, including intermediate markers of “risk” that influence breast pubertal development and age at menarche. The report also discusses “windows of susceptibility” during the life course when specific exposure(s) might have their greatest influence on lifetime breast cancer risk (e.g., in utero, puberty). • Forge partnerships with a variety of stakeholders. Many voices are needed in the breast cancer and environment discussion, including the voices of federal and nonfederal research funders, researchers, advocates, policymakers, communication professionals, environmental health specialists, and health care providers. This report examines the current ways in which these diverse groups interact and develop strategies for enhancing the exchange of ideas, practices, and intervention rates change in response to certain environmental factors strongly supports the role of modifiable (nongenetic) factors in breast cancer risk. For example, a twin study in a cohort of 10,000 women demonstrated that only 27 percent of breast cancer risk was attributable to heritable factors, leaving much to be explained by environmental influences.20 Studies of women who migrated from Asian countries to the United States showed that breast cancer rates in the migrant populations increased to become closer to those in the United States when migration occurred at younger ages21 and with increased time in the United States.22 The study by Ziegler and colleagues also found that women’s breast cancer risk increased with a greater number of grandparents born in the West. In addition, parts of the world that are developing or in transition (such as northern Africa) have sharply escalating breast cancer rates.23 Approaches for preventing cancer include reducing exposure to agents that increase risk,