Endocrine Disruptors—What Do They Disrupt?

In recent years, we have seen news items, television documentaries and debates about endocrine disruptors and the potential health risks they pose. In spite of their difficult name, these chemical compounds are much more familiar to us than we think because they form an integral part of our everyday life.

In spite of their difficult name, these chemical compounds are much more familiar to us than we think because they form an integral part of our everyday life

For example, they are the flame retardants in fabrics that make our clothes and upholstery more fire resistant, the perfluorinated coating on our frying pan that stops the omelette from sticking, the parabens that extend the life of cosmetics by preventing bacterial growth, and the bisphenol A used to line tin cans to prevent food from coming into direct contact with the metal surface. All of these chemical compounds, and many others, have the capacity to be endocrine disruptors. But what exactly does this mean?

For example: the parabens that extend the life of cosmetics by preventing bacterial growth, and the bisphenol A used to line tin cans to prevent food from coming into direct contact with the metal surface

What it means is that these compounds have a molecular structure very similar to that of our body's natural hormones, such as the oestrogen and thyroid hormones. Once these endocrine disruptors enter our bodies, via food or through our skin or the air we breath, they travel through the bloodstream and can mimic the action of our hormones. You will remember that, throughout our lives, hormones play a vital role in controlling many biological processes, including growth, puberty, and heart function. Thus, when an endocrine disruptor comes into contact with a target tissue that is prepared to receive a hormonal signal, it triggers the process that would have been triggered by the natural hormone. The tissue is unable to distinguish between the disruptor and the natural hormone.

In animal studies, endocrine disruptors have been shown to affect neural development and to increase the risk of obesity, diabetes and asthma. They have also been linked to certain malignancies, including cancer of the breast or prostate.

In humans, the evidence is not so clear. Although much research has been done, there is no conclusive epidemiological study on the effects of endocrine disruptors in people. What is more, scientists usually study the health effects of one particular endocrine disruptor, but in real life we are not exposed to a single endocrine disruptor but rather many of them at the same time. One of the greatest challenges facing researchers today is to find a way to analyse the totality of the environmental influences a person is exposed to every day.

In animal studies, endocrine disruptors have been shown to affect neural development and to increase the risk of obesity, diabetes and asthma

Our exposure to endocrine disruptors begins before we are born. During pregnancy, our mothers transferred many of these compounds to us through her blood; and during the first months of our lives we ingested them in maternal milk. Because their organisms are not sufficiently developed to eliminate these compounds, children are more vulnerable than adults to the action of the disruptors.  For that reason, our focus in ISGlobal is on studying the possible effects of endocrine disruptors on children's health. In the INMA Project (Childhood and Environment), we have seen that exposure to bisphenol A during pregnancy may increase the risk of obesity at age four as well as respiratory infections and wheezing throughout childhood. The aim of the HELIX Project (Building the Early-Life Exposome), a study involving 32 000 pairs of mothers and children in six European countries, is to identify all the environmental exposures affecting children during the early years of their lives and to link them with health, growth and developmental outcomes. Endocrine disruptors are among the environmental factors we are studying.

Although much research has been done, there is no conclusive epidemiological study on the effects of endocrine disruptors in people

Even though we still have only limited evidence in humans, we must ask ourselves whether it is necessary to live surrounded by so many chemical compounds, in plastics, cosmetics and pesticides. In recent years, the alarm raised about the possible health effects of endocrine disruptors has led manufacturers to seek substitutes for compounds such as bisphenol A. However, the molecular structures of the replacements are similar to those of the original molecules and, as a result, they may also be endocrine disruptors; in short, it is a catch-22 situation. That is why, as epidemiologists, we suggest that people should take precautionary measures until the scientific community has come to a unanimous and conclusive verdict. In other words, we advise people to try to avoid exposure to these compounds until they have been proven to be totally harmless.

As epidemiologists, we advise people to try to avoid exposure to these compounds until they have been proven to be totally harmless.

We all have an important role to play in this situation, but the task of elaborating and implementing policies that will prevent our exposure to these chemical compounds is really the responsibility of the institutions in charge of safeguarding public health.