Common consumer products may contain hundreds of chemicals that could increase our risk of developing breast cancer, scientists have warned. While some chemicals are known to directly cause cancer, many others indirectly promote the cancer by increasing our susceptibility to the establishment and growth of certain tumors. Breast cancer occurs when cells in the breast tissue grow out of control. Among the many risk factors associated with this disease is over-exposure to estrogen, progesterone and hormonal disruption. And it's not just hormonal contraception that can influence our body's hormone levels; numerous synthetic chemicals have been shown to disrupt our hormones, with potential impacts on our risk of developing various diseases. Breast cancer is a hormonal disease, so the fact that so many chemicals can alter estrogen and progesterone is concerning," Jennifer Kay, a research scientist at Silent Spring Institute, said. In a new study, published in the journal Environmental Health Perspectives, Kay and colleagues searched through multiple international and U.S. government databases to identify chemicals that had been found to cause mammary tumors in animals. In total, the team identified 921 chemicals that could potentially promote the development of breast cancer, 90 percent"or 829"of which are commonly included in consumer products, food, drinks, pesticides, medications and workplaces.