Reviews in Environmental Health, 1998
Environmental Health Perspectives 106, Supplement 1, February 1998

[Citation in PubMed] [Related Articles]

Environmental Endocrine Disruption: An Effects Assessment and Analysis*

Thomas M. Crisp,^1,2 Eric D. Clegg,^1,2 Ralph L. Cooper,² William P. Wood,² David G. Anderson,³ Karl P. Baetcke,³ Jennifer L. Hoffmann,³ Melba S. Morrow,³ Donald J. Rodier,³ John E. Schaeffer,³ Leslie W. Touart,³ Maurice G. Zeeman,³ and Yogendra M. Patel⁴

Part 1: Background

The U.S. Environmental Protection Agency (U.S. EPA) Risk Assessment Forum was established to promote scientific consensus on risk assessment issues and to ensure that this consensus is incorporated into appropriate risk assessment guidance. To accomplish this, the Risk Assessment Forum assembles experts throughout the U.S. EPA in a formal process to study and report on these issues from an Agencywide perspective. For major risk assessment activities, the Risk Assessment Forum has established technical panels to conduct scientific reviews and analyses. Members are chosen to assure that necessary technical expertise is available.

Recently, a number of ecologists, epidemiologists, endocrinologists, and toxicologists have called attention to the potential hazardous effects that estrogenlike and antiandrogenic chemicals and certain other environmental chemicals may have on human health and ecological well-being. A hypothesis has been proposed that certain chemicals may disrupt the endocrine system. These chemicals have been called endocrine disruptors because they are thought to mimic natural hormones, inhibit the action of hormones, or alter the normal regulatory function of the immune, nervous, and endocrine systems. Possible human health end points affected by these agents include breast cancer and endometriosis in women, testicular and prostate cancers in men, abnormal sexual development, reduced male fertility, alteration in pituitary and thyroid gland functions, immune suppression, and neurobehavioral effects.

In addition to potential human health effects, reports have accumulated that many chemicals released into the environment can disrupt normal endocrine function in a variety of aquatic life and wildlife. Some of the deleterious effects observed in animals have been attributed to persistent organic chemicals such as polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), dioxin, and some pesticides. Adverse effects include abnormal thyroid function and development in fish and birds; decreased fertility in shellfish, fish, birds, and mammals; decreased hatching success in fish, birds, and reptiles; demasculinization and feminization of fish, birds, reptiles, and mammals; defeminization and masculinization of gastropods, fish, and birds; decreased offspring survival; and alteration of immune and behavioral function in birds and mammals. It has been proposed that the above adverse effects may be due to an endocrine-disrupting mechanism.

The U.S. EPA has followed closely the recent reports dealing with the potential effects of environmental endocrine disruptors on human health and ecological well-being. The U.S. EPA's Science Policy Council requested that the Risk Assessment Forum prepare a technical panel report that would provide an overview of the current state of the science relative to endocrine disruption. It is intended that this report serve as an interim assessment to inform Agency risk assessors of the major findings and uncertainties and to serve as a basis for a Science Policy Council position statement.

Science Policy Council's Interim Position

The U.S. EPA is aware of and concerned about information indicating the possibility of adverse impacts on human health and the environment associated with exposure to endocrine disruptors. At the present time, however, there is little knowledge of or agreement on the extent of the problem. Based on the current state of the science, the Agency does not consider endocrine disruption to be an adverse end point per se, but rather to be a mode or mechanism of action potentially leading to other outcomes, for example, carcinogenic, reproductive, or developmental effects, routinely considered in reaching regulatory decisions. Evidence of endocrine disruption alone can influence the setting of priorities for further testing, and the assessment of the results of this testing could lead to regulatory action if adverse effects are shown to occur. This position could change as additional data become available on the mechanisms and role of endocrine disruptors.

The Agency thinks that identification of environmental agents that cause adverse effects as a result of endocrine disruption, as well as enhancement of our understanding of how these agents exert their effects, will improve the U.S. EPA's ability to reduce or prevent risks, particularly to children and vulnerable ecosystems. These considerations become increasingly important as we expand our risk assessment activities to incorporate a wider range of susceptible populations, multiple pathways of exposure, and mixtures of chemical substances.

Further research and testing are needed to address existing gaps in knowledge concerning the consequences of endocrine disruption. Such knowledge will reduce uncertainties in the assessment of hazard, exposure, and risk. The Agency is working with other federal agencies, as well as academic, international, and industry groups to expand the body of defensible and credible information and data on this issue. Several major activities are under way that address these needs. Examples of these activities are listed below.

• The U.S. EPA is co-sponsoring the detailed review and interpretation of the existing literature on endocrine disruption currently under way at the National Academy of Sciences' National Research Council. This study is expected to be completed in 1998.

• The U.S. EPA has developed and is implementing a multiyear endocrine disruptors research strategy.

• The U.S. EPA chairs the work group convened by the President's Office of Science and Technology Policy charged with the task to document and then coordinate research on endocrine disruptors across the federal government. Also, this activity serves as the basis for pursuing coordination of research on an international level.

• Under the mandates of the Food Quality Protection Act (FQPA) of 1996 and the 1996 amendments to the Safe Drinking Water Act, the U.S. EPA has established an advisory committee to assist in developing a screening and testing strategy for evaluating chemicals for their potential to cause effects via endocrine disruption. The FQPA requires that the strategy be developed and peer reviewed within two years, implemented during the third year, and that a progress report be submitted to the Congress by the end of the fourth year.

The U.S. EPA continues to stay abreast of scientific developments and will take regulatory action whenever sound scientific information and prudent public policy dictate. We are currently committed to pursuing domestic and international opportunities for exposure/risk reduction related to endocrine disruptors.

           

Last Update: March 18, 1998