Incorporating susceptible subpopulations in microbial risk assessment: pediatric exposures to enteroviruses in river water

The City of Stockton, California operates a wastewater treatment facility that discharges treated effluent to the San Joaquin River. During a recent discharge permit renewal, the question was raised whether pathogenic microorganisms in the effluent may cause an unacceptably high health risk for body contact recreation in the vicinity of the discharge. An investigation was initiated to characterize the risk to public health via body contact recreation in the San Joaquin River under various flow and treatment scenarios. In this investigation, a disease transmission model was applied to quantitatively characterize the relative risk associated with various treatment and flow scenarios for the City of Stockton's wastewater treatment facility. An important component of the investigation was to assess the feasibility of quantitatively characterizing the risk to highly susceptible subpopulations for effluent-related exposures to enteroviruses. This paper presents the methods used to conduct the feasibility assessment, the conclusions drawn for this project, and our recommendations to improve exposure assessments of susceptible subpopulations' contact with microbial pathogens in recreational water.