Post menopausal women who smoke or used to smoke have a 16% higher risk of developing breast cancer and there is a study that also says that women who have had extensive exposure to passive smoking, either as a child or as an adult, may also have an excess risk of developing breast cancer. There are many more things that can also increase your risk, such as drinking alcoholic beverages, estrogen, drinking non-organic milk, and being low in Vitamin D. Combine these things together and a woman is at an extremely high risk of developing breast cancer. Just living a healthy lifestyle will eliminate most of these risk factors.