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RATES OF GASTROINTESTINAL ILLNESS AMONG AREAS IMPACTED BY COMBINED SEWER FACILITIES: ANALYSIS OF MASSACHUSETTS DATA, 2003-2007
Citation:
RATES OF GASTROINTESTINAL ILLNESS AMONG AREAS IMPACTED BY COMBINED SEWER FACILITIES: ANALYSIS OF MASSACHUSETTS DATA, 2003-2007. To be Presented at Water and Health: Where Science Meets Policy Meeting, Chapel Hill, NC, October 03 - 07, 2011.
Impact/Purpose:
In this analysis we assess whether rates of emergency room (ER) visits for GI vary among areas impacted by CSS facilities in Massachusetts (MA). We hypothesize that towns near CSS facilities will demonstrate higher rates of GI compared to towns without nearby CSSs.
Description:
Previous studies have reported a temporal association between heavy rainfall and gastrointestinal infection (GI). Combined sewer systems (CSSs), which are present in many urban areas in the US, were designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. During normal operations, all wastewater is transported to a sewage treatment plant, where it is treated and discharged to a water body. However, during periods of heavy rainfall, the volume ofwastewater can exceed the capacity of the treatment plant, and wastewater discharges directly to nearby streams, rivers, or other water bodies. These overflows, called combined sewer overflows (CSOs), contain not only stormwater but also untreated human, animal and industrial waste and are a source of episodic pollution for downstream water users. Climate change is expected to increase the frequency of heavy episodic rain and resultant CSO events. In this analysis we assess whether rates of emergency room (ER) visits for GI vary among areas impacted by CSS facilities in Massachusetts (MA). We hypothesize that towns near CSS facilities will demonstrate higher rates of GI compared to towns without nearby CSSs. Data on location of CSS facilities in MA was obtained from the U.S. Environmental Protection Agency's (EPA) Enforcement & Compliance History Online System. Using these locations, each town in MA was classified into one of three categories: 1) a town with a CSS facility (24 towns, 18% of MA population); 2) a town potentially impacted by a CSS facility-those with surface water intakes or recreational water facilities located immediately downstream from a CSS facility (24 towns, 17%); and 3) a town not expected to be impacted by a CSS facility (307 towns, 65%). To assess GI, we utilized records ofER visits in MA from 2003 to 2007. Records with diagnoses of gastrointestinal infections (ICD9-CM 001-009, 558.7, 787.9) were abstracted and aggregated by town of residence. Annual population estimates by town were obtained from the U.S. Census and annual rates of ER visits for GI were calculated. Average annual rate of ER visits for Gl.in the towns with CSS facilities was 1476 ± 590 per 100,000 population compared to 1121 ± 740 for towns potentially impacted by a CSS facility and 1346 ± 1558 for towns not impacted by a CSS facility. To assess heavy rainfall events, we abstracted daily rainfall data from the National Climatic Data Center's 22 active MA weather stations during the study period. For all weather stations the mean daily rainfall was 0.15 inches (range: 0 -10.56). We conducted a sub-analysis comparing the 5 town area surrounding Boston (where recreational waters are impacted by CSS facilities; average annual rate ofER visits for AGI -1323 ± 365 per 100,000 population), the 9 town area near LowelllLawrence (where drinking waters are impacted by CSS facilities; average rate -1301 ± 857), and the 10 towns surrounding Worcester (which does not have any CSS facilities; average rate -1110 ± 383). This preliminary analysis demonstrates that areas impacted by CSS facilities areas experience higher rates of ER visits for GI compared to those without these facilities. We will further explore differences among CSS and non CSS impacted areas using time series analysis to draw associations between heavy rainfall events and daily ER visits for GI.. Additional work will also include evaluating approaches to define exposures to severe or high rainfall events, and evaluation of associations with flooding. With the prediction of increased heavy rainfall due to climate change it is important to understand the impact that combined sewer systems have on the surrounding communities. This abstract does not necessarily reflect EPA poicy.