In most plants and animals, hormones tell the cells what to do. This can include big changes, such as those caused by testosterone, estrogen and progestrone during puberty or pregnancy, or everyday tasks, such as abscisic acid telling plant cells to save water.
Endocrine disruptors are chemicals that can mimic hormones, or block them from transmitting these messages. As a result, they can interfere with normal biological processes. Endocrine disruptors have received a lot of attention because some of the processes controlled by hormones, such as puberty and pregnancy, are so critical.
There are lots of naturally occurring chemicals that are weak endocrine disruptors. Most plants and animals have evolved to be able to cope with natural levels of these chemicals. The scientific concern is more around stronger endocrine disruptors, and the total load that plants and animals – particularly humans – are exposed to.
For example, it is common for endocrine disruptors to mimic estrogen. While our bodies are able to cope with exposure to a few chemicals that weakly mimic estrogen, exposure to a lot of chemicals which mimic estrogen could overwhelm these coping mechanisms. It has been suggested that high loads of endocrine disruptors that mimic estrogen could be to blame for things like falling sperm counts in more affluent countries.
While there are numerous chemicals in personal care products that can mimic estrogen, studies have shown that the vast majority of estrogen mimicking chemicals in the environment come from use of the contraceptive pill. When a woman takes the contraceptive pill, she will excrete some of the hormones in her urine. Ultimately, these end up being released to the environment in treated waste water.
As a result, the contribution of endocrine disruptors in personal care products to total environmental loads is comparatively low. Aquatic toxicity testing generally allows scientists to evaluate stronger endocrine disruptors on their individual merits – the toxic effects that come from interfering with normal biological process should show up here.
Endocrine disruption is an important consideration. If there is information to suggest a chemical might be an endocrine disruptor, I will check for the results of studies that can show whether this could cause a toxic effect and say if the chemical is toxic to aquatic life. But because of this, endocrine disruption itself is not discussed at length in the reviews.