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Sanitary Sewer Systems and Association with Gastrointestinal Illness: A case crossover analysis of Massachusetts Data, 2006-2008
Citation:
Jagai, J., G. Smith, C. Lin, E Hilborn, AND Tim Wade. Sanitary Sewer Systems and Association with Gastrointestinal Illness: A case crossover analysis of Massachusetts Data, 2006-2008. Presented at Society for Epidemiological Research, Boston, MA, June 18 - 21, 2013.
Impact/Purpose:
Application of a case-crossover study to investigate the association between sanitary sewer overflows and emergency room visits for gastronitestinal illness
Description:
Sanitary sewer overflows (SSOs) occur when untreated sewage is discharged into water sources before reaching the treatment facility potentially contaminating them with gastrointestinal pathogens. Causes of SSOs include heavy rainfall and rupture/blockage of sewer lines. Few studies have quantified the risk associated with SSO events in the United States. We conducted a case-crossover analysis to assess the association between SSO events and emergency room (ER) visits for gastrointestinal illness (GI). ER visits for GI (n=370,319) for the years 2006-2008 were obtained from the State of Massachusetts, Division of Health Care Finance and Policy (defined per ICD-9CM codes). SSO events were obtained from the Massachusetts Department of Environmental Protection. A case-crossover analysis was used with each case (ER visit) representing their own control for the city of Lowell, MA. Lowell receives drinking water from the Merrimack River, which is affected by SSO discharges. Two control periods were matched for each case; 21 days before and 21 days after the admission date. Cases and controls were considered exposed if an SSO event occurred within the previous five days and unexposed if there was no SSO event. Data were analyzed using a conditional logistic regression. In Lowell there were 76 documented SSO events and 3,152 ER visits for GI in the time period. For all GI visits there was no association with SSO events: 8.7% of cases and of 9.4% of controls occurred in the three days following an SSO event (Odds Ratio, OR = 0.91, 95% Confidence Interval, 95% CI 0.78-1.06). Among those over 75 years of age there was an elevated but statistically insignificant association (OR=1.75; 95% CI 0.82-3.72). This analysis demonstrates utility of the case-crossover approach in studying extreme events. Additional analyses will be conducted to evaluate associations in other communities with different water sources. (This abstract does not necessarily reflect EPA policy.) Character count (with spaces): 1983/1985