After the Fall: Gastrointestinal Illness following Downpours.

Abstract

Many older cities have “combined” sewer systems that collect both sewage and stormwater runoff in the same pipe for transport to a wastewater treatment plant. During heavy rainfalls, these combined systems can become overloaded, and water utilities must discharge the excess—what’s known as a combined sewer overflow (CSO)—into rivers and other water bodies, which may be the local source of drinking water. Bacteria, viruses, and protozoa in these untreated releases can cause waterborne diseases.1 In this issue of EHP, researchers report that emergency room visits for gastrointestinal (GI) illnesses increased after heavy rainfalls in areas of Massachusetts served by combined sewer systems, offering evidence that CSOs may adversely affect human health.2