This week's Topic In Depth focuses on the controversial subject of the effects of synthetic chemicals on hormonal systems and their potential impact on many aspects of human health.

The first site (1) is a Why Files introduction to the endocrine system, the problem of endocrine disrupters, and what is being done to evaluate chemicals for endocrine disruption potential. Next is a Web site(2) from the authors of Our Stolen Future, a 1996 book that brought this subject to the public forefront; the site contains up-to-date information on the debate. A brief page (3) provided by Physicians for Social Responsibility, Inc. answers some questions about endocrine disrupters in general terms. A fact sheet (4) from the National Science and Technology Council focuses more on the research that is being conducted. Two sources that give more in-depth information about endocrine disruption research are the Biological Resources Division of the US Geological Survey (5), which describes field research on the effects synthetic chemicals may have on wildlife, and the US Environmental Protection Agency (6), which is attempting to develop standardized chemical testing procedures to aid in regulatory decision making. The next resource is a Web sitesponsored by The Society of the Plastics Industry, Inc. (7) that gives information on bisphenol A, a chemical used to make some types of plastic, in either general or technical language. Lastly, a new Web sitefrom the Natural Resources Defense Council (8) is a rich resource that focuses on the subject of chemicals that accumulate in breast milk, several of which are suspected endocrine disrupters.