'The eyes of the world are on this race'. Paris Olympics' triathlon hangs in the balance over E. Coli levels in the Seine

Triathlon athletes dive in the Seine river during the men's 2023 World Triathlon Olympic Games test event in Paris in August 2023. (Bertrand Guay / AFP)

A reference point for Parisians and tourists alike, the River Seine will be the crown jewel of the Olympics this summer, staging events such as the triathlon as well as the opening ceremony, which for the first time in Olympic history will not be taking place in a stadium.

Starting at Pont Alexandre III Bridge, the individual triathlon races are set to begin with a 1.5-kilometer swim, followed by a 40K bike race – passing by the Le Grand Palais and Champs-Elysées – before finishing with a 10K run through the heart of the city.

A mixed team relay race involving four athletes – two men and two women – will also start at Pont Alexandre III Bridge with each team member completing a 300-meter swim, followed by a 5.8K bike ride and 1.8K run.

If all goes to plan, it will be a historic moment, given that swimming in the Seine has been illegal for more than 100 years due to the river’s pollution levels, though some swimming has been permitted recently as part of triathlon test events. But some are warning that there are still potential dangers lurking below the river’s shimmery surface.

Recent testing results shared with CNN by technology company Fluidion show that the Seine is still not safe for swimming as per the standards set by World Triathlon, due to high E. Coli bacteria levels in the water, potentially exposing athletes to serious health risks.

Authorities have spent at least €1.4 billion ($1.55 billion) to clean up the Seine. Last month, a rainwater storage facility was opened that can hold 20 Olympic swimming pools worth of water to reduce pressure on the sewage network and lower the risk of wastewater being discharged into the Seine, according to a statement from Paris 2024.

Meanwhile, triathlon teams around the world are preparing for the worst and hoping for the best.

“For me, it will be very frustrating and very shaming for France, Paris and the Olympics if we can’t do a triathlon,” French-born triathlete Jeanne Lehair told CNN in a telephone interview.

What does the latest testing show?

The city of Paris is working with its own laboratory to monitor the Olympic Seine site, but technology company Fluidion, founded in Paris in 2012, has also been checking the water quality of the river several times a week at Pont Alexandre III Bridge.

The Seine serves as Fluidion’s primary research site, according to the company, hence why they routinely collect water samples for internal research efforts. CNN has not independently verified the organization’s findings.

Fluidion’s testing has found that, on average, E. Coli levels in the Siene between early April and late May were just under 3400 MPN/100mL. According to CNN’s calculation, this is more than three times higher than the level needed for “good” water quality, as per World Triathlon standards.

“We have experienced a very rainy past couple of months, causing numerous combined sewer overflows in Paris and upstream,” Dan Angelescu, CEO of Fluidion, told CNN on May 31 via email, adding that the impact on water quality is evident, with “noticeable bacterial spikes following storm events.”

Nearly all of France has seen 120 to 200% of normal rainfall over the past three months, with numerous episodes of flooding across portions of the country, especially the north, according to Météo France.

The highest E. Coli levels recorded by Fluidion were 23590 MPN/100mL on May 2 and 13090 MPN/100mL on May 30, according to Angelescu. The May 2 result is more than 20 times higher than World Triathlon’s “good quality” level, according to CNN’s calculation.

More recently, following several days of dry and sunny weather, E. Coli levels on Monday 6 June were 2280 MPN/100mL, according to Angelescu, better than previous results but still above acceptable levels for swimming.

If E. Coli levels remain this high, the swimming leg of the triathlon will have to be cancelled, according to World Triathlon competition rules, unless the organization’s medical committee decides that the race can go ahead.

Does Paris 2024 have a plan B?

Earlier in June, World Triathlon told CNN in an email that the first contingency plan would be to delay the race by one day. But if poor water quality persisted, the triathlon would have to be downgraded to a duathlon with no swimming, the organization confirmed.

Angelescu said that while E. Coli is not typically pathogenic itself, it can indicate the presence of other pathogens, which can cause skin rashes, diarrhea, serious gastrointestinal diseases and, in very rare cases, even death.

However, Angelescu said that the water quality of the Seine is likely to improve significantly before July due to drier and sunnier summer conditions, which will reduce the frequency of sewage spills.

“It is highly speculative and scientifically unsound to project any conclusions about water quality during the Games based on recent trends,” he said.

Angelescu said that “significant infrastructure projects” by the city of Paris designed to improve water quality will have a “substantial” impact.

“These tanks are expected to become operational before the Games, potentially becoming a … Games changer,” added Angelescu.

“When our instruments and data indicate that the water quality is good, we will be the first to dive in, headfirst!”

Angelescu’s tone of optimism isn’t universally shared.

French charity Surfrider Foundation Europe warned in April that they were “genuinely concerned about the health of athletes” after only one of the 14 samples collected by the organization indicated a satisfactory standard of water quality for swimming.

Two months later, the charity told CNN that they have since taken five additional samples, with E. coli levels remaining “systematically above the guide values.” CNN has not independently verified the charity’s findings.

How has Paris 2024 responded to these findings?

Paris 2024 said they still have “great confidence” in the city of Paris to improve water quality to the “necessary standard” in time for the Games.

“Generally, water quality in the Seine continues to improve every day,” they said in a statement to CNN in early June. “By the time of the Games, bacteriological pollution in the Seine will have been reduced by 75% thanks to the range of actions undertaken by our partners.”

In a statement to CNN, the city of Paris said that recent grey and rainy conditions have had a “major impact” on the Seine’s water quality. A lack of sunlight – which would normally help to kill bacteria – has also contributed to the poor quality, they said earlier this month.

They added: “It is only when summer conditions (strong sunshine, high temperatures, prolonged absence of rain) become established that the Seine will gradually return to its ‘summer’ appearance, and that we will see a gradual and significant improvement in water quality.”

Following multiple days of sunny weather in the first week of June, E. Coli levels improved near Pont Alexandre III Bridge, according to official data from the city of Paris shared with CNN, but whether the good weather will last remains to be seen.

No precipitation trend, higher or lower than average, has been predicted for areas around Paris for the summer.

Since June 1, E. Coli levels declined from around 7000 UFC/100mL (equivalent units to MPN/100mL, according to World Triathlon) to just below 1000 UFC/100mL on June 9, according to official data.

However, World Triathlon’s Competition Rules 2024 say that these levels are still too high for swimming, unless the organization’s medical committee decides that the race can go ahead.

Disinfectant and probiotics

The threat that E. Coli and other bacteria pose is nothing new to triathlon teams.

Over the last decade, water quality issues have been increasingly encountered, according to Mike Cavendish, Director of Performance at British Triathlon, who outlined preventative measures British athletes will be taking to ensure their health during Paris 2024.

“Disinfectant sounds like a really basic thing but it’s something we will be doing a lot of, making sure that athletes are clean, that their equipment is clean,” Cavendish told CNN in a telephone interview.

Probiotic yogurts can also help to improve gut health, Cavenish added.

Phil Dunne, Triathlon Canada’s High Performance Director, said in a statement to CNN that their athletes are being supported by “a team of physicians and dietitians” to reduce the risk of becoming sick due to “compromised” water quality.

Tim Harradine, CEO of AusTriathlon, said that triathletes are used to dealing with the “changing nature” of waterways.

“Sometimes they race in the rain, sometimes they race in the heat,” Harradine told CNN in a telephone interview, adding that athlete health will always come first.

Lehair, who recently changed her nationality in time to represent Luxembourg at Paris 2024, told CNN that she understands why precautions need to be taken, but didn’t seem altogether convinced by the effectiveness of measures like probiotics.

“It’s supposed to be good for the body anyway, so maybe you can have a try but it’s not 100% sure that you won’t get sick if you take probiotics,” she said. “At least maybe you are stressing a bit less on the day of the race.”

‘Better quality of water is good for everyone’

Paris 2024 isn’t the first sporting event to contend with water quality issues.

In March, concerns were raised after E. coli bacteria was discovered in London’s River Thames ahead of the historic Oxford and Cambridge boat race. Also, in 2016, drug-resistant superbugs from hospital sewage were found in Rio de Janeiro’s Guanabara Bay.

Lehair is pleased that the authorities are attempting to clean up the river, but just wishes it had happened sooner. “They should have done this much before, just for the quality of the water in general and for the people, for the city,” she said. “Better quality of water is good for everyone.”

Cavendish said that if the authorities’ clean-up efforts in Paris prove successful, other countries could be encouraged to follow suit.

“If they pull this off and it looks fantastic, and they get a swim for the Olympics and the Paralympics … it puts pressure on other governments around the world, including our own, to try and make sure that we get safe swimming,” said Cavendish.

Harradine echoed that sentiment: “It’s a very visible race venue and what a great legacy it could leave if this works well for the city.”

And if the worst comes to the worst and the impact of rain on water quality does threaten the triathlon races Cavendish is confident that the right call will be made. “The eyes of the world are on this race so I think you can guarantee that they (Paris 2024 and World Triathlon) will be putting all the right people in the room to make the right decision,” he said.

CNN’s Weather Team and Bea Adeleke contributed to this report.