What are endocrine disruptors?

In 2002, the World Health Organization (WHO) along with the International Programme on Chemical Safety (IPCS) proposed the following definition of an endocrine disruptor:

An endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub)populations.

This internationally accepted definition of an endocrine disruptor has two very important pieces: first, that the substance alters the function of the hormonal system, and second, by doing so causes an adverse effect (i.e. toxicity). The likelihood that a substance will cause harmful effects on the endocrine system is based on its potency (how active it is) and potential for exposure (how large the dose is, the frequency with which exposure occurs and the duration of the exposure). The definition is important so as not to confuse “endocrine effects” with “endocrine disruption,” with the latter term being linked to adverse effects.

Why make a distinction between endocrine activity and disruption?

A precise definition is important because the majority of the substances that may interact with the endocrine system result in activity that is, or in some cases, even essential to our well-being. Terms becoming popular in media reports mislabel many chemicals as “endocrine disrupting chemicals” or “EDCs,” when, in fact, scientific study is still under way or does not support such labels. From a regulatory policy and scientific perspective, it is important to focus on those substances that have a real potential to cause harm to people or the environment.

What is the U.S. EPA doing about endocrine disruptors?

In response to public concern that certain environmental chemicals may interfere with endocrine processes in humans, the U.S. Congress passed the Food Quality Protection Act and amendments to the Safe Drinking Water Act in 1996. These laws directed the U.S. EPA to develop and implement a program to investigate the potential for substances to cause adverse health effects through endocrine pathways.

Shouldn’t we be concerned about any endocrine or hormone changes?

The endocrine system naturally responds to exposures from our environment, both chemical and physical. In the case of chemical exposures, the endocrine system responds to both natural (e.g., food) and synthetic sources of chemicals. For example, a change in temperature, food, or daylight can affect the level of hormones circulating through our body. Most of these changes are harmless and necessary to allow our bodies to adjust to an ever-changing environment as we undertake our normal daily activities.

Don’t synthetic chemicals pose more of a threat than natural substances?

It is a common misunderstanding to assume a synthetic chemical is more hazardous than a natural one. At the molecular level – where chemical interactions occur – the body does not differentiate between natural and synthetic substances with respect to potential effects.

What about the dose of exposure to the chemicals? Can lower doses of chemicals, which may be lower than the doses used to conduct animal toxicology testing, cause endocrine disruption?

Contrary to the well-established principle that “the dose makes the poison,” some scientists and advocacy groups allege that in certain circumstances, a different dose-response interaction can possibly occur with alleged endocrine disrupting chemicals (EDCs). The researchers speculate that a more significant response could occur at a low dose, compared to that observed at higher doses. These “low-dose effects” are postulated to occur at doses well below those levels previously tested and determined to be safe by regulatory authorities. The question of whether some chemicals can cause a biological response and negative health effects at these very low-dose levels is embodied by the “low-dose hypothesis.”  This idea is contrary to the well-established principle of “dose response relationships,” which is the cornerstone of drug development in modern pharmacology and safety assessment in modern toxicology.

Are you suggesting we don’t need to worry about substances that affect our hormones?

No, but we shouldn’t misinterpret the significance of endocrine effects, either. The biological activity of any substance can be positive, neutral or negative. Hormonal activity by itself does not imply a health risk to a living organism, unless it can be shown to lead to harmful effects.