Sanitary Sewer Overflows and Association with Gastrointestinal Illness: A case crossover analysis of Massachusetts Data, 2006-2007

Sanitary sewer overflows (SSOs) occur when untreated sewage is discharged into water sources potentially causing contamination. SSOs are primarily caused by heavy rainfall, which is expected to become heavier and more episodic due to climate change. We conducted a case-crossover analysis to assess associations between SSOs and emergency room (ER) visits for gastrointestinal illness (GI). SSO events were obtained from Massachusetts Department of Environmental Protection. ER visits for GI for 2006-2007 were obtained from State of Massachusetts, Division of Health Care Finance and Policy (abstracted by ICD-9CM codes). We restricted the analysis to towns with majority of SSO events: Boston, Lowell, Framingham, Revere, and Waltham and stratified for five age categories. Each case (ER visit) represented their own control and was matched to a control period 15 days prior to the start of SSO event and matched on town and year. Cases and controls were considered exposed if an SSO event occurred within the previous four days and unexposed if there was no SSO event. Data were analyzed using a conditional logistic regression and stratified by town and age group. There were 197 SSO events for 2006 -2007 in the 5 towns and 18,948 total ER visits for GI. Overall, there was an increased odds of ER visits for GI (OR = 1.25; 95% CI (1.16, 1.36)) for all age groups and all towns combined. However, results varied by town and age group with the highest odds ratios demonstrated in the 0-10 years age category. Future work will consider details regarding the nature and severity of SSO events. With the expected increase in variability of rainfall due to climate change and aging infrastructure in parts of the U.S., it is important to understand the impact of heavy precipitation events on human health.  (This abstract does not necessarily reflect EPA policy.)