Does atrazine cause breast cancer in laboratory animals?
What we call the breast in humans is called the mammary gland in laboratory animals. Feeding high levels of atrazine to mice or one type of female rat did not result in a higher number of mammary gland tumors in these animals. However, when tested in another type of rat, several studies found either a higher number or earlier appearance of mammary gland tumors in the female rats fed a moderate to high level of atrazine over long periods of time. These rat studies suggest that atrazine could be a possible breast cancer causing agent. The reason why atrazine caused mammary tumors in one type of rat is currently being debated and studied. Some researchers believe that atrazine may cause changes in the levels of substances carried in the blood called hormones. These hormonal changes may play a role in the development of the mammary tumors in rats fed atrazine. Other researchers have not been able to show that atrazine causes hormonal changes that would explain the higher number of mammary
