More Olympic athletes to compete in the Seine River, here’s the latest on water quality concerns

PARIS — A major question at the Paris Olympics was whether the water quality of the Seine was safe enough to host swimming competitions.

The amount of bacteria in the river is constantly fluctuating, so water samples are taken daily so that organisers can assess the risk and decide whether swimming in the long-polluted Parisian waterway should go ahead.

Triathletes raced in the river on Wednesday, and tests will determine whether upcoming events will go ahead as planned, including the mixed triathlon relay on Monday and the swimming marathons scheduled for Thursday and Friday.

Here are some things to know about testing the water quality of the Seine:

Why does the number of bacteria matter?

High levels of E. coli and enterococci indicate contamination of water with sewage or feces. Most strains are harmless, and some live in the intestines of healthy people and animals. Others, however, can be dangerous.

Even drinking large amounts of contaminated water can cause diarrhea and, consequently, diseases such as urinary tract or intestinal infections.

A person’s susceptibility to illness from exposure to E. coli depends on several factors, the most important of which are the person’s age and general health.

“Generally speaking, the healthier you are, the more likely you are to be able to fend off any pathogens,” said Brian Rahm, an expert in biological and environmental engineering at Cornell University.

Sometimes it’s not even the E. coli itself that’s a concern, Rahm said. “When we see E. coli in the water, that means that other types of pathogens and other bacteria, viruses, could be in the water as well.”

The tests help organizers assess the risk to athletes, but they are difficult to accurately determine risk, said Metin Duran, a professor of civil and environmental engineering at Villanova University.

“Unfortunately, there is little you can do before exposure to reduce your risk,” Duran said.

Swiss officials said Saturday that triathlete Adrien Briffod, who had competed in the Seine three days earlier, had developed a stomach infection. They said, however, that it was “impossible to say” whether it was related to his river swim, and that other delegations had told them that none of their triathletes had reported stomach problems.

Why does the bacteria count change?

The water quality of the Seine is closely linked to the weather. Heavy rain causes sewage and runoff to flow into the river, causing bacteria levels to rise, while the sun’s ultraviolet rays can kill bacteria.

There have already been several heavy rains during the Paris Games.

To cope with these unforeseen circumstances, Paris has earmarked €1.4 billion ($1.5 billion) for infrastructure improvements ahead of the Olympics, including building a massive reservoir to collect excess rainwater and prevent sewage from flowing into the river, upgrading the sewage infrastructure and upgrading wastewater treatment plants.

Deputy Mayor of Paris Pierre Rabadan said the improvements made had produced major results.

“We will never prevent the impact of rainfall on water quality. It is impossible,” he said. “What we have done will allow us to return to water quality that is satisfactory and good, as was the case for triathlon.”

Organisers cancelled a number of test swims this weekend and last week to allow triathletes to familiarise themselves with the course due to concerns about water quality after rain. The men’s triathlon was postponed a day and then held on Wednesday, the same day as the women’s race.

If water quality is not safe, organizers may postpone Monday’s mixed relay triathlon until Tuesday. If concerns persist, the swim race will be canceled and athletes will compete only in running and cycling.

How is water quality considered safe if it is

on race day?

Decisions to cancel events are made early in the morning on race day, and that’s what’s expected for Monday’s mixed relay. Organizers are considering taking samples from the river 21 1/2 hours earlier to give time for lab cultures to develop.

Rabadan said infrastructure improvements were preventing sewage from flowing into the Seine. It was raining on Wednesday when the triathletes competed. Sewage flowing into the river upstream would take several hours to reach Paris, meaning water quality levels were still safe for the race, he said.

Since then there has been heavy rain on Thursday evening and on Saturday evening as well.

Paris 2024 Olympic spokeswoman Anne Descamps said on Sunday that organisers “hopefully we will be able to organise the competitions tomorrow and we will make a decision, as planned, tomorrow morning.”

What is included in the tests?

Daily water quality tests measure levels of fecal bacteria, including E. coli. The World Triathlon Water Safety Guidelines and the 2006 European Union Directive assign quality values ​​to a range of E. coli levels.

According to World Triathlon guidelines, E. coli levels of up to 1,000 colony-forming units per 100 millilitres can be considered “good” and allowed to compete.

World Triathlon called the 2006 European Union directive “the most comprehensive guidelines for bathing water” in an email, based on the range of factors it considers. Other organizations, including the U.S. Environmental Protection Agency, have set a limit of 126 units per 100 milliliters of water and say higher levels are not suitable for recreational use.

The World Triathlon Medical Commission said that when deciding to organize a competition on the river, it takes into account water quality analysis, sanitary control and weather forecast.

The day after Wednesday’s race on the Seine, data released by World Triathlon showed that a sample taken at 6 a.m. Wednesday on the Pont Alexandre III, the bridge where the swim begins and ends, came back with a level of 249 units. Samples from other points along the course had similar levels.

Are the tests used during the Games sufficient?

Dan Angelescu, founder and CEO of Fluidion, a Paris-based technology company that monitors water quality, says the tests are “flawed” and “significantly underestimate the number of bacteria.”

Fluidion tests the water several times a day, and Angelescu said, “We see that the water quality is not as good as the measurement data published by the city suggests,” resulting in an “underestimation of the real risk.”

The company measures both “free-floating” bacteria in water and takes a “comprehensive” level, which Angelescu said also includes bacteria attached to fecal particles or sediment. He said the comprehensive measurement provides a more complete picture than the lab test the city uses.

He compared it to looking at a busy road with pedestrians, motorcycles, cars and buses and trying to count all the people. The city’s method, he said, is similar to counting from a helicopter and weighing each person or vehicle equally, because you can’t see how many people are in each car or bus. He says his comprehensive test is more like a police officer stopping every vehicle and counting every person in the car or bus to get a full count.

Angelescu said he discussed the discrepancies with city officials and that they decided to continue with the standard lab method they were using, which complies with the regulations. It was “a fair decision under the regulations,” he said. “The problem is that the regulations are wrong.”

Rahm of Cornell University said that ultimately, “from a public health perspective, it doesn’t matter whether it’s circulating freely or trapped in a dirt particle. Either way, it’s going to get into your body.”

___

Naishadham reported from Washington. Contributing authors included AP writers Jeffrey Schaeffer in Alfortville, France, and Angela Charlton, John Leicester and Ahmed Hatem in Paris.