Officials at the National Institute of Environmental Health Sciences on Wednesday added steroidal estrogens used in oral contraceptives and in hormone replacement therapies to the government's list of "known human carcinogens," The Wall Street Journal reports. Estrogen was added to the list based on a review of medical literature over the past two years showing that the compound boosts a woman's risk of endometrial and breast cancers and heart disease, said Christopher Portier, director of the Environmental Toxicology Program for the institute. Although estrogen was added to the list of potential cancer-causing agents, scientists remain unsure whether the compound still poses a cancer risk when combined with other hormonal agents in birth control pills and hormone replacement therapy. The list also does not make any recommendations about whether estrogen products should or should not be used. Portier says that advice should come from a physician.