The 2024 Paris Olympics opening ceremony on July 26 was met with heavy rain, and subsequent downpours over the weekend reportedly drove an uptick in disease-causing bacteria in the Seine River. This decline in water quality prompted officials to cancel the swimming portion of a triathlon training session and postpone the men’s race scheduled for July 30.
Finally, on July 31, both the women’s and men’s triathlons were allowed to proceed, with athletes plunging into the Seine for a 0.9-mile (1.5 km) swim before the cycling and running legs. France and Great Britain snagged gold in the respective races, but concerns remain as the mixed relay and marathon swimming events are set for next week.
Poop Pollution and Bacteria Levels in the Seine
Paris invested $1.5 billion to make the Seine swimmable for the Olympics, including connecting thousands of homes to the sewer system and building a massive underground cistern to prevent untreated sewage from flowing into the river. However, heavy rain can still overwhelm the combined sewer system, diverting untreated wastewater into the Seine.
This leads to spikes in bacteria like Escherichia coli (E. coli), which is found in both human and animal feces. “Elevated E. coli levels are to be expected following rain events,” said Sarah Lowry, a Stanford University environmental engineering doctoral candidate.
E. coli serves as an indicator of fecal contamination, implying the presence of other poop-borne pathogens like norovirus and Salmonella. While these bacteria and viruses typically decline within days due to factors like sun exposure and water temperature fluctuations, the timeline depends on upstream runoff, land use, and drainage systems.
Potential Health Risks for Olympic Athletes
World Triathlon, the governing body for triathlons, deems E. coli levels above 900 colony-forming units per 100 milliliters (CFU/100mL) as unsafe for swimming in inland waters. Data showed E. coli at 985 CFU/100mL in the Seine two weeks before the Games, slightly exceeding this threshold.
Swallowing contaminated water can lead to gastrointestinal issues, dehydration, and potential infections. Most E. coli strains are harmless, but some can cause more serious illnesses. The risk depends on an individual’s immunity and exposure level.
Experts recommend swimmers avoid swallowing water, wear protective gear like goggles, and shower after swimming to mitigate health risks. With more rain forecast, the Seine’s water quality may continue fluctuating, potentially impacting upcoming Olympic events.