We don't know much about chemical interactions nor all the other chemicals which are as yet untested. In the last 5-10 years, new research has shown that certain chemicals in modern society do mimic estrogen in the test tube. These chemicals can come from sources that we previously thought were inert such as plastics that might be used to package food and detergents. Some animals in the environment also show evidence of hormone disruption . Presently, we do not know what these test tube studies mean for us.
Human bodies can act differently.
Unfortunately, only a small fraction of chemicals have been tested for estrogen mimicking effects, and these chemicals are active at infinitesimal small quantities way below what was previously thought to affect humans. Estrogen mimicking chemicals can also act synergistically to amplify each other or even block each other. This is widely known, but exact synergistic reactions and levels at which they occur are virtually unknown. Chemicals in our environment having estrogenic effects known as xenoestrogens are now being investigated by the Environmental Protection Agency .