Submitted to: American Journal of Public Health
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/30/2013
Publication Date: 4/1/2014
Citation: Uejio, C.K., Yale, S.H., Malecki, K., Borchardt, M.A., Anderson, H.A., Patz, J.A. 2014. Drinking water systems, hydrology, and childhood gastrointestinal illness in central and northern Wisconsin. American Journal of Public Health. 104:639-646. Interpretive Summary: When pathogens contained in animal manure and human wastewater are released to the environment, weather events such as rainfall or snowmelt can cause pathogens to move, potentially exposing people to disease transmission. We studied the medical records of nearly 5,000 children located in two regions of Wisconsin over a 19-year period and found that, for those children living in municipalities whose source of drinking water was untreated groundwater, precipitation was positively correlated with increased rates of gastrointestinal illness. In the summer and fall, during weeks with 1.2 inches of rain, children were 40% more likely to have a gastrointestinal illness; and during very wet weeks with 4.7 inches of rain, the risk of illness increased 140%. We did not observe this relationship between precipitation and illness rates for children living in municipalities with treated drinking water or for children living in rural households with private wells. Knowledge of how weather events affect pathogen movement and when drinking water supplies are most vulnerable to pathogen contamination will help public health officials determine corrective actions and prevent disease transmission.
Technical Abstract: Background: Current United States drinking water regulations create areas with different levels of water quality. Municipalities accessing untreated groundwater and households with unmonitored private wells may be at increased risk for acquiring waterborne disease. Objectives: The study investigates if the type of drinking water source (treated municipal, untreated municipal and private well water) modifies the effect of hydrology on childhood gastrointestinal illness. Gastrointestinal incidence may be related to hydrology in systems without treatment or failing infrastructure if drinking water is the primary exposure route to waterborne pathogens. Methods: We conducted a retrospective time series study to assess the relationship of hydrologic and weather conditions to childhood (age < 5) gastrointestinal illness from 1991-2010. The Marshfield Epidemiologic Study Area, located in Central and Northern Wisconsin, includes households using all three types of drinking water systems. Separate time series models were created for each drinking water system and half year period (winter/spring, summer/fall). Results: More precipitation (summer/fall) systematically increased childhood gastrointestinal illness in municipalities accessing untreated water. The relative risk of contracting gastrointestinal illness was 1.4 in weeks with 3 cm precipitation and 2.4 in very wet weeks with 12 cm of precipitation. In contrast, gastrointestinal illness in private well and treated municipal areas was not influenced by hydrologic conditions. Conclusions: Our study suggests that improved drinking water protection, treatment, and delivery infrastructure may improve public health by identifying, in particular, municipal water systems without water treatment that may transmit waterborne disease.