Low Dose Hormone Like Chemicals may Harm

Low doses of endocrine disrupting chemicals may not be safe

April 4, 2012 / Author:  / Reviewed by: Joseph V. Madia, MD

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Endocrine-disrupting chemicals (EDC) is the name given to a variety of substances that can act like hormones in the body.  Exposure to EDCs can occur through contact with a variety of common household goods and in many industrial settings. 

The effects of high-doses of EDCs are well-studied in industrial settings, but the possible health effects of low-dose exposures, like those in common household goods, have not received as much attention.

EDCs in the Household

Synthetic EDCs are found in a wide variety of plastics, pesticides, fungicides, and medicines.  Naturally occurring EDCs are found in human and animal foods.

One widely publicized EDC is bisphenol-A (BPA), which is used as an additive in plastic bottles commonly used for drinking water. Some research shows that contact with BPA through touch or through food and beverages that are stored in BPA plastics may be harmful. BPA is linked to harmful effects on the brain and behavior of developing fetuses, infants, and children.  Other studies found no harmful effects. Many companies now use BPA-free plastic for drinking bottles because of the health effects that may be caused by exposure to this chemical.

Naturally occurring EDCs, sometimes called phytohormones, are found in many foods.  Foods made from soy contain a substance called phytoestrogens. Many health benefits have been found for moderate intake of phytoestrogens including relief from some symptoms of menopause, prevention of certain cancers, and treatment of some symptoms of osteoporosis. Excessive intake has been shown to cause reproductive issues in farm animals and research animals.

Another class of EDCs, phthalates, is found in some flooring materials, some medical devices, cosmetics, and some plush toys.  The FDA published a warning that infants, especially male infants, should avoid contact with the medical devices containing the phthalate Di(2-ethylhexyl)phthalate (DHEP) because it might cause problems with normal development of male sexual organs. Some states and countries have banned the use of phthalates in toys.

EDCs in the Body

Hormones are important for many bodily functions including emotional regulation, sexual development, sexual reproduction, and maintaining heart rate and blood pressure. The human body has receptors that are designed to react to hormones circulating in the blood stream. Very small amounts of hormones are needed in the blood to activate these receptors for normal bodily function.  

EDCs are small and can bind to receptors in the body that are sensitive to the body’s own endocrine hormones – like estrogen, testosterone, and cortisol (a stress hormone). When EDCs bind to these receptors, they can interrupt normal function in a few ways.  EDCs can bind to the receptor and stimulate functions similar to the naturally released hormone.  EDCs can also bind to the receptors and block them from being used by naturally released hormones. In these ways, EDCs can interfere with the normal functions of the body and its hormone processes.

High doses of EDCs are linked to certain cancers, reproductive problems, immune system problems, and early puberty. The products available for household use are regulated to contain only low-doses of EDCs, doses that are considered safe.

New Developments and Public Policy

A recent review article examined the research about the health effects of low-dose exposure to EDCs.  The paper reviewed over 800 studies of low-dose effects of EDCs. Lead author Laura Vandenberg, Ph.D., stated: “These studies focused on the effects of chemicals at low doses – doses that humans are exposed to in their regular lives, that are thought to be safe. Our analysis indicates that these chemicals, called EDCs, are not in fact safe at these low doses.”

The authors of this paper note that the idea of low and high doses may need to be realigned.  The body is designed to respond to very low levels of its natural hormones that are released into the blood. Therefore, contact with low-doses of EDC may still be enough to be active at the receptors and create health effects related to this receptor activity.

Current polices restrict high-dose exposures to many EDCs that are known to be harmful. However, low-dose exposures are not regulated because the doses are deemed safe.  The bringing together of many different studies shows that even low-doses could be harmful. Low-dose exposure to EDCs in household items deemed “safe” is common. Repeated contact with low-doses may be harmful in ways that a single exposure is not. 

Dr. Vandenberg also noted, “High doses should not be used to ‘predict’ or ‘calculate’ the effects of low doses – instead, the doses that are proposed to be safe should be tested. And regulatory agencies shouldn’t look only at whether chemicals kill or maim, but whether they alter development, reproduction and endocrine health.”

The review was published online March 14, 2012 ahead of print for the June issue of Endocrine Reviews.

No conflicts of interest were disclosed. The study was supported by grants from NIH, Susan G. Komen for the Cure, the Mitchell Kapor Foundation, the Cornell-Douglas Foundation, the Wallace Global Fund, and the Kendeda Foundation.