High levels of disease-causing bacteria found in Potomac River after major sewage spill

University of Maryland researchers have detected extremely high levels of disease-causing bacteria in the Potomac River following a massive sewage spill last month, raising what scientists describe as urgent public health concerns about risks from the nation’s aging infrastructure.

Water samples collected by the research team revealed E. coli levels more than 10,000 times above EPA recreational water quality standards at the spill site.Staphylococcus aureus was also detected at multiple locations along with MRSA, an antibiotic-resistant strain, identified at the sewage overflow site.

The contamination stems from a Jan. 19 pipe rupture that released hundreds of millions of gallons of raw sewage into the Potomac River. Researchers describe the incident as one of the largest sewage spills in U.S. history.

Dr. Rachel Rosenberg Goldstein, a microbiologist and assistant professor at UMD’s Department of Global, Environmental, and Occupational Health, led the testing through her Water Quality, Outreach and Wellness Lab. Her team began collecting samples shortly after the spill and returned a week later with members of the Potomac Riverkeeper Network.

“People coming into contact with the impacted water or land are at risk of becoming infected with these bacteria, which can lead to serious health conditions,” Dr. Goldstein said in a UMD press release. “Although most people are not swimming in the frozen river in February, bacteria can survive in freezing temperatures and become active again when temperatures rise.”

The initial samples taken Jan. 21 at the spill site showed E. coli concentrations exceeding recreational water quality standards by more than 10,000 times. A week later, levels at the same location remained over 2,500 times above safe limits. Even at a site more than 10 miles downstream, E. coli levels measured 1.5 times higher than EPA standards.

The team also found Staphylococcus aureus, the bacteria responsible for staph infections, at the overflow site and at a location nine miles away. Of all sites tested, 33 percent were positive for the pathogen, higher than typically found in other surface waters containing the bacteria. MRSA was identified at the site of the sewage overflow.

Dr. Goldstein advised residents near the spill site in Maryland, Washington, D.C. and downstream areas to avoid contact with the affected water and land until bacteria levels return to safe standards. Anyone exposed should wash skin thoroughly with soap and water and launder clothing in hot water.

The incident highlights a broader national problem. Up to 75,000 sewage overflows occur annually across the United States, according to UMD’s Water Emergency Team, which Dr. Goldstein co-leads with Dr. Marccus D. Hendricks, an associate professor of Urban Studies and (Environmental) Planning.

Mr. Hendricks’ research in Washington, D.C. shows that above-ground development has outpaced infrastructure improvements, straining outdated sewer and stormwater systems.

“Investment, maintenance and rehabilitation of drainage and other water resources infrastructure have been slow and the effects of this are clear in this Potomac sewage spill,” Mr. Hendricks said. “National reporting has consistently shown over time that water resources infrastructure, such as stormwater and sewer systems, are underfunded compared to other essential systems like transportation.”

Despite recent federal infrastructure legislation, including the 2021 Bipartisan Infrastructure Law, Mr. Hendricks said similar incidents will likely continue due to chronic underfunding and the massive scale of needed repairs.

“This issue isn’t going away – solving the recent Potomac spill is not a simple one-time fix. We need significant and ongoing investment in system upgrades and maintenance,” Mr. Hendricks said.

The Water Emergency Team continues to collect water and soil samples in the affected area, working directly with community organizations to share findings with residents and local policymakers.