Personal care products that contain estrogens or xenoestrogens may increase breast cancer risk Maryann Donovan a , Chandra M. Tiwary a , Deborah Axelrod c , Annie J. Sasco b , Lovell Jones d , Richard Hajek d , Erin Sauber a , Jean Kuo a , Devra L. Davis a, * a Center for Environmental Oncology, University of Pittsburgh Cancer Institute, University of Pittsburgh, Graduate School of Public Health, Department of Epidemiology, UPMC Cancer Pavilion, Fourth Floor, 5150 Centre Avenue, Suite 432 Pittsburgh, PA 15232, USA b University Victor Segalen Bordeaux 2, INSERM U 593, Team of Epidemiology for Cancer Prevention, 146 rue Leo Saignat, 33076 Bordeaux cedex, France c Community Cancer Education and Outreach, New York University Clinical Cancer Center, New York, New York, USA d M.D. Anderson Cancer Center, Center for Research on Minority Health, University of Texas, USA Received 15 September 2006; accepted 20 September 2006 Summary Established models of breast cancer risk, such as the Gail model, do not account for patterns of the disease in women under the age of 35, especially in African Americans. With the possible exceptions of ionizing radiation or inheriting a known genetic mutation, most of the known risk factors for breast cancer are related to cumulative lifetime exposure to estrogens. Increased risk of breast cancer has been associated with earlier onset of menses or later age at menopause, nulliparity or late first parity, use of hormonal contraceptives or hormone replacement therapy, shorter lactation history, exposure to light at night, obesity, and regular ingestion of alcohol, all of which increase circulating levels of unbound estradiol. Among African Americans at all ages, use of hormone-containing personal care products (PCPs) is more common than among whites, as is premature appearance of secondary sexual characteristics among infants and toddlers. We hypothesize that the use of estrogen and other hormone-containing PCPs in young African American women accounts, in part, for their increased risk of breast cancer prior to menopause, by subjecting breast buds to elevated estrogen exposure during critical windows of vulnerability in utero and in early life. These early life and continuing exposures to estrogenic and xenoestrogenic agents may also contribute to the increased lethality of breast cancer in young women in general and in African American women of all ages. Public disclosure by manufacturers of proprietary hormonally active ingredients is required for this research to move forward.  c 2006 Elsevier Ltd. All rights reserved. 0306-9877/$ - see front matter  c 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.mehy.2006.09.039 * Corresponding author. Tel.: +1 412 623 3375; fax: +1 412 623 3201. E-mail address: davisdl@upmc.edu (D.L. Davis). Medical Hypotheses (2007) 68, 756–766 http://intl.elsevierhealth.com/journals/mehy