Inland recreational waters—state of the science in epidemiologic studies. This anchoring of the QMRA predictions will enhance their sci- entific credibility for predicting recreational waterborne illness. Longer-term research. Modeling water quality in real time. Long-term research is required to characterize the transport, fate, and persistence of microbes and their molecular targets in sediments and soils. Understanding how these variables change as a function of solar radiation, rainfall, and biotic and hydrologic factors will advance our ability to develop mechanistic models for watershed management and set pollutant discharge limits. Pollutant source as a determinant of health risk in IW. New epidemiologic stud- ies would fill the data gap that currently pre- cludes directly comparing the FIB-health risk relationship in coastal and IW. Ideally, several inland sites should be selected, each with a different type of dominant source of fecal pol- lution. Description of both illness rate and illness severity will be important to more com- pletely characterize risk. Health data should be collected in conjunction with data on indi- cators and pathogens in surface waters and sediments using conventional and emerging microbial detection methods. QMRA should be performed in tandem with the epidemio- logic studies. Conclusions We endorse the development of science-based criteria to protect the health of those who use marine, Great Lakes, and riverine and lacustrine recreational waters. We think that the distinction of IW versus CW is of less importance than more fundamental vari- ables such as the scale of the body of water, the source of the pollutant, and the effects of sediment, which translate into differences in the densities, transport, and fate of indi- cators and pathogens. Differences in these variables between IW and CW may translate into weaker indicator–pathogen and indi- cator–health risk relationships for IW com- pared with CW. It remains an open question whether sediment in IW changes the rela- tionship between enterococci qPCR measures and health risk, which has been described at coastal beaches impacted by human fecal pol- lution. A challenge in addressing health risks is the imprecision in defining of risk, as frequent mild illness (seen in coastal epidemiologic studies) may be of less public health concern than infrequent severe illness (described in outbreaks of disease in IW). We suspect that the application of coastal-derived criteria should result in rates of sporadic mild illness that are no higher (and possibly lower) in IW than CW. We are concerned about outbreaks of severe disease caused by fecal matter from Appendix 1. Critical questions for IW criteria development 1) Microbial indicators as predictors of pathogen exposure and health risks. What are the transport, fate, persistence, and regrowth characteristics of indicators and pathogens in climatically and hydrologically diverse IW? 2) Fecal pollution sources as predictors of pathogen exposure and health risk a) Pathogen exposure • What are the prevalence, concentration, and virulence of human pathogens in fecal matter from birds, livestock, and wildlife mammals? • What is the likelihood that the various animal sources will pollute IW (proximity, scale)? • How does fecal pollutant source modify the FIB-pathogen relationship? b) Health risk: how does fecal source modify indicator–health risk relationships? 3) Molecular methods for water quality testing a) What are optimal test methods in terms of sensitivity, specificity, accuracy, and precision? How can PCR inhibitors best be addressed? What markers perform best for source identification? b) The interpretation of rapid FIB measures of indicators: what are the relevant molecular targets that predict pathogen density and/or health risk in IW? Do viable cells detected by qPCR better predict risk than nonviable cells or cell-free DNA? How is the ratio of these three fractions impacted by wastewater treatment and environmental variables? c) How can molecular methods be standardized and simplified for widespread implementation? 4) Other approaches to predicting IW recreation health risks a) QMRA validation: how do QMRA predictions compare with epidemiologic observations? How can QMRA methods and inputs be improved? b) Mechanistic and regressions models of water quality • Can coastal approaches for modeling FIB be optimized for IW? • Can real-time models predict pathogen exposure and health risk? c) How can sanitary surveys, as a means of characterizing indicators, pathogens, or pollutant sources in IW, be validated and standardized? Environmental Health Perspectives • volume 118 | number 6 | June 2010 other bathers, wildlife, and livestock. In IW with limited dilution capacity and close prox- imity to sources, outbreaks of severe disease may be difficult to prevent by the applica- tion of coastal-derived criteria (this was not a conclusion of the workshop and represents the authors’ views). As critical research ques- tions are answered, a basis will be established for developing criteria that would afford a similar level of protection in IW as in CW, at least for mild sporadic illness. 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