Environmental Engineering and Endocrine Disrupting Chemicals

Endocrine disruptors are a class of chemicals of growing interest to the environmental community. The U.S. Environmental Protection Agency’s ~EPA! Risk Assessment Forum defined an endocrine disrupting chemical ~EDC! as ‘‘an exogenous agent that interferes with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body that are responsible for the maintenance of homeostasis, reproduction, development, and/or behavior’’ ~EPA 1997!. Most of us are more familiar with chemicals of concern that have a specific health outcome such as lung cancer. However, EDCs are a class of chemicals defined by their mode of action and can result in a variety of health outcomes. For example, an EDC can initiate a health-related outcome in humans or wildlife by binding to and stimulating estrogen or androgen receptors. Gaining a thorough understanding of the endocrine-related effects of chemicals on humans and wildlife is the goal of domestic and international research that will continue far into the future. The Global Endocrine Disruptor Research Inventory ~EPA 2001a! indicates over 600 human and wildlife health effects studies currently underway. The Food Quality Protection Act requires the U.S. EPA to build a screening and testing program to identify those industrial chemicals that cause endocrine-related effects to human and wildlife health ~see http://www.epa.gov/scipoly/ oscpendo/index.htm!. To obtain results for existing industrial chemicals will likely take most of this decade. However, the literature already points to some chemicals as likely endocrine disruptors including certain phthalate esters, particular biodegradation products of octylphenol and nonylphenol polyethoxylate surfactants, several specific PCBs, some chlorinated dioxins, DDT and DDE, bisphenol A, tributyltin, the pesticides methoxychlor and endosulfan, and exogenous steroid hormones, among others. Studies are also underway, worldwide, to characterize the levels of suspected endocrine disruptors to which humans and wildlife are exposed ~EPA 2001a!. Once adequate effects and exposure information are collected, the risk of individual or mixtures of endocrine disruptors can be assessed. Some political bodies have begun to implement risk management strategies for EDCs. For example, the European Union and some individual European nations have banned or are phasing out the use of some endocrine disruptor-related chemicals such as nonylphenol polyethoxylate surfactants and certain phthalate esters. Decisions on how and when to begin actively managing or reducing unacceptable risks posed by EDCs must be determined by stakeholder organizations. Whether or not to apply risk management tools to an EDC-related environmental problem depends on currently available risk information, available management technologies, their economic impact, and social and political factors. Some level of uncertainty is always associated with risk management decision making. The earlier risk management tools are applied to reduce exposure to a chemical of concern, the greater the level of uncertainty. However, early application of risk management tools can reduce exposure of humans and wildlife while additional and more detailed information is acquired. As more information about the chemical of concern is obtained ~e.g., levels in the environment, effects on human and ecosystem health, specific sources, etc.!, risk management decisions are made with less uncertainty. Our role as research and development environmental engineers is to provide engineering information to stakeholders so that decisions on the application of risk management tools or processes can be made with minimal uncertainty. The input we can provide regarding EDCs includes the following: ~1! identification of currently available tools that can be adapted to lower exposure of humans and wildlife to EDCs; and ~2! development of new approaches to reduce exposure if adequate tools are not readily available. Environmental engineering research on managing exposure to EDCs has begun in the last several years. This initial work is an international effort addressing, among others, the following questions: