One route yields a very weak form of estrogen that is excreted from the body. Other routes produce forms of estrogen that may be cancer promoting. Heptachlor itself does not act like estrogen. However, heptachlor does affect the way the body breaks down estrogen in the liver. Scientists have not yet determined if heptachlor causes breakdown of estrogen into the more cancer-promoting form or the less harmful form.
Cells use many different ways to monitor and control their growth.
As a consequence, there are many different ways by which a chemical like heptachlor may be able to disrupt cell growth control and promote cancer. While growing in the body, or in a laboratory on a plastic dish, cells need to communicate with neighboring cells to regulate their growth. By disrupting this growth regulation mechanism, heptachlor could affect cancer growth. Since heptachlor epoxide can build up and be stored in breast fat, human milk can carry this chemical from a mother to a breast-fed infant. At the levels of heptachlor epoxide contamination that have been found in breast milk samples in the U.S., researchers have concluded that the beneficial effects of breast feeding an infant far outweigh the estimated risk for cancer.