So-called endocrine effects of environmental chemicals, or endocrine disruptors, have been in the news for the past year and a half. You've probably seen the headlines—"Sperm counts declining," "Mating patterns in birds altered in the Great Lakes," or "Studies point to fearsome chemical risks." These headlines may entice readers, but the scientific questions surrounding endocrine disruption are just beginning to be answered.
The human body requires hormones to drive basic metabolic functions. Several organs produce hormones in the body—adrenal, hypothalamus and pituitary glands, ovaries and testes. Hormones are important for mental function, reproduction and other physiologic processes. These important hormones are naturally produced by the body, and when deficient, are frequently replaced by pharmaceutical drugs, for example, post-surgical thyroid replacement therapy or post-menopausal hormone replacement therapy which have significant beneficial health effects for some people.
In the laboratory, scientists have been examining the effects that environmental chemicals have on human hormones in relation to health. Much of the research has been conducted only in test tubes, with little research focused on the effects on animals or humans. Thus, many scientific theories have been extrapolated to describe potential human problems.
The questions about endocrine disruption are clouded by the fact that many of the findings that have appeared in news headlines have not been able to be reproduced by the same researchers or by researchers in other laboratories. One example of this lack of scientific reproducibility was a study conducted by Tulane University scientists and reported in the June 1996 issue of Science. The study purported that the effects of four pesticides exhibited a thousand-fold increase in endocrine disrupting potency in combination, compared to when they were tested alone and no effects were observed. The researchers attempted but they could not replicate the findings in a subsequent experiment. The authors retracted their earlier research findings in a letter to Science in July 1997 (see the September/October 1997 Food Insight).
In addition, there are hormonally active components of foods we eat every day such as soy, barley, cabbage and corn. The good news is that while hormonally active, these plant components exhibit no negative hormonal effects in humans. In fact, many beneficial properties of these compounds in foods are being researched for their potential health effects, including reducing the risk of some cancers.
To systematically address the question of endocrine disruption in environmental chemicals, the U.S. Environmental Protection Agency (EPA) announced that it will begin an evaluation of some 15,000 compounds used in thousands of common products, ranging from pesticides to plastics. The work of EPA's Endocrine Screening and Testing Advisory Committee (EDSTAC) began in 1996, following passage of the Food Quality Protection Act and the Safe Drinking Water Act. Both laws included provisions directing the agency to establish a screening and testing program for chemicals suspected of disrupting the endocrine system.
In October 1998, EPA released the EDSTAC report and recommendations. The report includes recommendations that will serve as the basis for a formal screening and testing program for endocrine activity of environmental chemicals.
The EDSTAC recommended that the EPA's screening and testing program should:
- Address both human and ecological (wildlife) effects;
- Examine effects on estrogen, androgen, and thyroid hormone-related processes; and
- Evaluate endocrine disrupting properties of both chemical substances and common mixtures.
When announcing the report, Lynn Goldman, EPA assistant administrator for toxic substances said, "Testing chemicals on this scale for endocrine disruption has never been done before. Although technologically challenging, when testing systems are in place, it will allow for major improvements in public health protection."
The EPA screening and testing program will submit chemicals to a series of screening assays which will then help the agency prioritize the chemicals for additional tests. Chemicals that test negative in the screening process may not need further testing. The agency has begun to develop a complex protocol for testing suspected endocrine disruptors.
EPA and the scientific community also are awaiting the results of an independent study about endocrine disruptors from the National Academy of Sciences' (NAS) Committee on Hormonally Active Agents in the Environment. The NAS study is expected to be available by the end of the year or in early 1999.
Taken together, the NAS report and the EPA's screening program will strengthen the science base surrounding endocrine disruption and, hopefully, allay consumers' concerns.
The EPA EDSTAC report can be found on the Internet at http://www.epa.gov/oscpmont/oscpendo/history/keystone.htm.
