Citing Lack of Data, EPA Calls for More Study of Endocrine Receptors

Citing Lack of Data, EPA Calls for More Study of Endocrine Receptors
June 1, 1997

In its first evaluation of the scientific research on the effects of endocrine disruptors on human health and the environment, EPA has determined that the controversial subject warrants further study.

EPA's review, Special Report on Environmental Endocrine Disruptors: An Effects Assessment and Analysis, is based on the agency's evaluation of three hundred peer-reviewed studies of the effects of certain chemical and other environmental agents suspected of disrupting the hormonal or endocrine systems of humans, laboratory animals, and wildlife. The report was prepared by a panel of EPA scientists assembled by the agency's Risk Assessment Forum.

"The findings contained in our assessment send a strong signal for more research on the effects of endocrine disrupting chemicals, particularly into their possible effects on humans, where we currently do not have enough information to conclusively determine the potential risks of existing exposures," commented Robert Huggett, EPA assistant administrator for the office of research and development.

An endocrine disruptor is an external agent that interferes in an as yet not fully understood way with the role of natural hormones in the body. An agent might disrupt the endocrine system by affecting any of the various stages of hormone production and activity, such as by preventing the synthesis of hormones, by directly binding the hormone receptors, or by interfering with the natural breakdown of hormones.

The subject of endocrine disruptors gained no small amount of national attention last year with the publication of Our Stolen Future: Are We Threatening Our Fertility, Intelligence, and Survival? by Theo Colborn and others. Our Stolen Future outlined in rather sensational terms how exposure to hormone-disrupting chemicals might be adversely affecting human and animal reproduction systems.

Though the book received, at best, mixed reviews in scientific journals, the uproar created by its message was enough to persuade Congress last year to establish an advisory committee within EPA, including representatives from industry and other stakeholders, to develop a cooperative screening and testing program to study the effects of endocrine disruptors. The Congressional action was taken in connection with adoption of the Food Quality Protection Act and reauthorization of the Safe Drinking Water Act.

No Immediate Regulatory Consequences

The just-released report is the EPA advisory committee's first analysis of the effects of endocrine disruptors, and, given its inconclusive nature, must be something of a disappointment to those who expected immediate regulatory responses from Our Stolen Future’s message. Specifically, the report highlights the need for more information on the intensity, frequency, and duration of human exposures to chemicals that have been demonstrated to disrupt the endocrine systems of animals. The report notes the need for more research on the effects of chemical mixtures with endocrine-disrupting potential, and calls for a strengthening of specific cause-and-effect data.

In the wildlife studies reviewed, the report concludes that it should be determined whether the adverse effects noticed in animals at various sites across the country are confined to isolated areas or are representative of more widespread conditions. Groups of organisms for which there is some evidence of endocrine disruption include snails, oysters, fish, alligators, and other reptiles as well as birds, such as gulls and eagles.

Although effects have been observed, generally it has been difficult to prove that a specific chemical caused a particular endocrine effect, the report notes. Wild organisms are exposed to a variety of chemicals and non-chemical sensors, complicating the identification of a definitive cause. In many cases, the report points out, the chemicals associated with effects have already been identified as problem substances due to their toxicity and persistence and, therefore, are heavily regulated or banned for commercial use in the United States. Examples include DDT, PCBs, and certain heavy metals.

It is difficult to discern whether endocrine effects on individuals of a particular species have affected populations of that organism or the community of which it is a part, the report says. According to the report, the most creditable examples illustrating significant declines in population as a result of exposure to endocrine-disrupting chemicals have been reported in alligators in central Florida and some local populations of marine invertebrate species.

A Step to "Toxic Outcomes"

Given the current state of the science, EPA does not consider endocrine disruptors to be "an adverse endpoint per se," but a "step that could lead to toxic outcomes, such as cancer or adverse reproductive effects." The reference to the possibility of "toxic outcomes" is particularly significant in light of the report's finding that there is a "need for chemical screening guidelines, and for more exploration into the potential effects of endocrine disruptors in sensitive populations, including children."

In September 1996, EPA announced that it would be paying special regulatory attention to what it referred to as children's special vulnerability to environmental pollutants. In late February, the agency established its Office of Children's Health Protection. The office will address what EPA says is a "wide array of complex threats to children's health, from air pollution that can exacerbate asthma to toxic chemicals that can lead to serious health problems."

As EPA delves further into the area of endocrine disruptors, it would not be surprising to see its first regulatory proposals undertaken with a clear reference to children's special vulnerability in this area.
To obtain a copy of EPA's report, contact the agency's Office of Research and Development at 513/569-7562. The report is also available on the Internet at http://www.epa.gov/ORD/whatsnew.htm.