siderable controversy as to whether human health has also been adversely affected by exposure to endocrine-active chemicals because of inconsistent and inconclusive results. Dose-response relationships are likely to vary for different chemicals and endocrine disrupting mechanisms, and such relationships may be species dependent. The exposure sets that do exist are primarily from chemical levels in various environmental media such as air, food, or water and may not reflect internal concentrations in blood or endocrine-regulated tissues. Exceptions to this are human breast milk and adipose tissue (e.g., Swan et al., 2005). Overall, more research is needed. It remains difficult to assess the risk to human and animal health from endocrine disruptors due to the necessity to extrapolate from low-dose exposures. An additional difficulty in assessing risk from endocrine disruptors is the possible synergistic effect from other environmental hazards. Because controversy will continue to surround EDCs and their potential short- and long-term risks to environmental and human health and welfare, EDCs remain an “emerging issue.”

There is a rich array of opportunities for earth and public health scientists to collaborate on research that addresses health and drinking water quality. The earth science component of this research relates to improving the understanding of sources, transport, and transformations of potentially hazardous substances in water to ultimately determine the concentrations to which people are exposed through their drinking water. The health components of the research relate to quantifying and understanding the mechanisms of human responses to these exposures. The overall goal in all cases is to be able to predict potential health effects based on improved process-based understanding and, where appropriate, through modeling. Prediction of potential adverse health effects will provide the basis for development of effective prevention or mitigation measures related to either the water source or the human health response. High-priority collaborative research activities are to:

1. Determine the health effects associated with water quality changes induced by technologies and other strategies currently being implemented, or planned, for extending groundwater and surface water supplies to meet increasing demands for water by a growing world population. Of particular interest with respect to groundwater are changes in water quality induced by:

   • changes in rates and locations of groundwater extraction;

   • treatment of sewage effluent for potable reuse;