Risk of Gastrointestinal Disease Associated with Pathogen Exposure in the Lower Passaic River

Abstract

P-716 Introduction: During precipitation events, untreated human sewage in combined sewer overflow (CSO) systems is often intentionally discharged to surface water bodies to avoid overload of water treatment plants. Some studies have concluded that CSO discharges can cause pathogen-related disease in human populations and as a result, the U.S. Environmental Protection Agency (EPA) has recently initiated litigation against municipalities for inadequately controlling CSO discharges. In this analysis, we evaluate the pathogen risk associated with CSO discharge into the Lower Passaic River, New Jersey. Historical water monitoring data and sampling results taken near CSO discharge areas were used to establish representative microbial concentrations in surface water. These concentrations were used to quantify the risk of different diseases for various exposure scenarios. Methods: Concentrations of fecal coliform, total coliform, fecal Streptococcus, and fecal Enterococcus were estimated from water samples collected at various locations from the River on six different days (n=36) in 2004. To characterize CSO concentrations, one water sample was collected directly from and in the immediate vicinity of a discharging CSO during a precipitation event at a CSO in Newark, New Jersey (n=2) and analyzed for the above indicator bacteria, Giardia, and several viruses. Risk estimates for gastro-intestinal disease were calculated using geometric mean concentrations and well-established dose-response relationships. Three scenarios were considered: visitor (angler, boaters), recreator (swimmers, rowers), and transient (homeless individuals living along the River). Results: Nearly all of the pathogen concentrations measured in the Passaic River exceeded health-based water quality criteria, sometimes by several orders of magnitude. Giardia[r] cysts were detected in both CSO samples at levels similar to those reported for raw sewage. The visitor and recreator scenarios were associated with a 28% probability of gastrointestinal illness due to fecal coliform and a 4% probability due to fecal Streptococcus or fecal Enterococcus. For the transient scenario, Giardia exposures were predicted to yield a nearly 100% probability of infection, as well as nearly a three-fold increase in the risk of infection from fecal coliform and a 5.5% probability of gastrointestinal illness due to fecal Streptococcus or fecal Enterococcus. Conclusions: Water samples collected from the Passaic River contained pathogen concentrations that far exceeded health-based criteria. This risk analysis suggests that contact with Passaic River surface water is and will continue to pose a significant pathogen risk until the CSO discharges are controlled or abated.