Levels of contamination in the Seine remain unsafe for Paris Olympians, report says

Levels of contamination in Paris’ River Seine remain unsafe for Olympians to compete with just over a month remaining before the games, according to a monitoring report from the city of Paris. 

The report found elevated levels of E. coli bacteria — an indicator of fecal matter — in routine samples collected at several sites along the Seine from June 10 to 16.  

During the Olympics, Paris plans for athletes to compete in the Seine for marathon swimming and triathlon events. The first such event is the men’s triathlon, which is scheduled for July 30, according to The Associated Press.

To make that possible, Paris spent about $1.5 billion to clean up the city’s old sewer system, which discharges into the river during bouts of heavy rainfall. But the new report suggests those efforts might not have been enough. 

The International Olympic Committee and Paris 2024, the local organizing group in Paris, did not immediately respond to inquiries from NBC News. 

Last year, test events of triathlon and marathon swimming in the Seine — designed to make sure the Olympic competitions run smoothly — were canceled after the river failed pollution tests in August.

The weather can play an outsized role in pollution in the Seine. According to the new report, exceptional rainfall in May and rainy days last week diminished water quality significantly. The report also noted that there have not been sunny days or periods with lower streamflow, which can help reduce bacteria. 

“The sun does inactivate the bacteria,” said Helena Solo-Gabriele, a professor in the University of Miami’s department of chemical, environmental and materials engineering. 

Unsafe levels of fecal matter in water where athletes swim could cause gastrointestinal disease, Solo-Gabriele added. 

Conditions in the Seine have been under scrutiny for months. The nonprofit Surfrider Foundation Europe released independent results from six months of tests and found almost all samples failed permitted levels of E. coli and enterococci — two types of bacteria that scientists typically test for as a measure of fecal matter. 

“High bacteria means there’s too much poop in the water and poop carries germs that make people sick,” said Daniel Nidzgorski, an ecologist who monitors water quality for King County in Washington state. 

He added, though, that many people don’t realize most strains of E.coli are harmless and that research suggests hospitalizations due to swimming-related illnesses are rare.

Paris Mayor Anne Hidalgo and French President Emmanuel Macron have pledged to take a swim in the Seine’s waters to prove their cleanliness, but that has not yet happened. 

Paris is not the first city to face issues with bacteria when hosting the Olympics. In the lead up to the 2016 games, an Associated Press analysis found that at Olympic sites in Rio de Janeiro, levels of viruses and bacteria from fecal contamination were up to 1.7 million times what would be considered safe for some U.S. beaches. Officials from the Brazilian government and IOC acknowledged that the waters were contaminated but said locations where athletes would compete met World Health Organization standards, according to The New York Times.

“There are a lot of impaired waters. It’s an issue everywhere where there’s urbanization and where you don’t have natural flushing for the environment to dilute out the bacteria,” Solo-Gabriele said. 

Experts said the Olympics draws particular attention to these challenges every four years.

“Hopefully this draws attention to a problem of river contamination that needs to be addressed every day, not just for Olympic athletes,” said Karen Levy, a professor in the University of Washington’s Department of Environmental & Occupational Health Sciences. 

NBC News is a division of NBCUniversal, which owns the U.S. media rights to the Olympic Games through 2032, including the 2024 Paris Games, which begin on July 26.