The study compared cadmium levels in the urine of 246 breast cancer patients with 254 age-matched women in a control group, and found that the women with cadmium levels above a certain level were 2.29 times more likely to have breast cancer than women with lower levels of cadmium.
Dr. Jane A. McElroy, the study's lead researcher, said cadmium has already been classified by the U.S. Environmental Protection Agency as a likely cancer-causing substance. However, the study could not determine if the elevated levels of cadmium were a cause of the breast cancer, or a result of already having cancer.
McElroy says it is unclear how cadmium could cause breast cancer, but she believes it mimics the effect of estrogen on the body, which can increase a woman's risk of breast cancer. According to McElroy, if her study's findings can be replicated in a larger study, it could result in tighter restrictions on how cadmium is disposed of in the environment.