Why is it so complicated to know the quality of water?

The water in the Seine is decidedly very murky. New data published by Mediapart on Wednesday, August 7, show that the water in the Parisian river was of sufficient quality for swimming only between 10 and 20% of the time between July 26 and August 5. These revelations once again undermine the rhetoric of public officials who claim that the Seine is now swimmable, while refusing to publish the figures and health advisories that allow this to be verified.

For the past two weeks, it has been very complicated, if not impossible, to access water quality analyses of the Parisian river. The Organizing Committee for the 2024 Olympic Games (Cojo) has only been releasing a few results in dribs and drabs. Paris City Hall and the Ile-de-France prefecture have cut off the taps of their own weekly bulletin launched in June. The Ile-de-France Regional Health Agency also refuses to share the health advice it was asked to provide by the region’s prefecture. As for researchers and specialists, they themselves do not have access to the analyses.

As the 2024 Olympic Games draw to a close, franceinfo takes stock of the reasons why it is so difficult to know the quality of the water in the Seine.

1 Because the bacteriological analyses are not published

The authorities have seen things on a grand scale to monitor the Seine. Since the beginning of the summer, the water of the Parisian river has been analyzed at 35 different sampling points spread upstream, downstream and in the capital. Four of these analysis points are located on the Olympic site alone, between the Pont Alexandre III and the Pont de l’Alma. These are subject to very specific monitoring: analyses have been carried out there twice a day since June 1, according to the newspaper The Team. But there is no point in looking for the results of these samples. They are not made public, or only partially.

Questioned last March, Marc Guillaume, the prefect of the Ile-de-France region, promised to demonstrate transparency. “Of course, in one form or another, perhaps with a delay of a few hours, but obviously there is no reason why the quality of the water should not be made public”he replied during a press conference (statement at 16’50 min).

Since June, the City of Paris has published a weekly bulletin entitled “Météo de la Seine”. This publication was partial: it only gave the results of four sampling points out of the fortnight available to the city and these analyses were published with a one-week delay. Asked in June by franceinfo about the possibility of consulting the missing data, the municipality referred to “a publication at the end of the year”.

But since the start of the Olympic Games, even the weekly bulletin of the City of Paris has been interrupted. Questioned by franceinfo, the city hall explains that “During the Games, the publication of the results of the tests on the Olympic sites is the responsibility of Paris 2024.” She also specifies that she “will resume publishing its weekly bulletin on Fridays, as has been the case since the beginning of June. The next one will include all the data from the Olympic Games period on the four points tested by the City.”

For its part, the Cojo did not communicate the analyses it had during the two weeks of competitions. When contacted by franceinfo at the end of July, the organizers of the Olympic Games referred us to the sports federations, who also did not comply with our request. The only information made public was now that communicated during the press briefings of the organizers of the Olympic Games, and only when training or a competition took place. These communications only mentioned simple ranges of bacteriological results, without specifying the locations of the samples, or all of the results for the days concerned. However, some of these analyses kept secret were finally made public on Wednesday, August 7 by Mediapart. They show that the quality of the Seine has remained very largely insufficient since the start of the Olympic Games. Between July 26 and August 5, the water was unfit for swimming between 80 and 90% of the time, depending on the regulations applied.

2 Because the Regional Health Agency does not communicate its health advice

In France, when you want to swim in a body of water, you must refer to the opinions of the Regional Health Agency (ARS) to find out whether swimming is dangerous or not for your health. It is in this sense that, since the beginning of the summer, the prefecture of the Ile-de-France region has requested two advisory health opinions from the ARS of Ile-de-France. The first was issued on July 12. It had been requested with a view to authorizing swimming in the Seine from the mayor of Paris, Anne Hidalgo, and the prefect Marc Guillaume, on July 17. A second health opinion was issued on July 24, this one with a view to holding the triathlon and marathon swimming events during the Olympic Games.

But it is impossible to know what these health notices contain. Questioned by franceinfo Thursday August 8, The ARS refuses to share them. It refers to the prefecture, which also does not transmit the requested documents. It is also impossible to know the conclusions of these opinions. The ARS refuses to specify whether they are favorable or unfavorable to swimming in the Seine.

These documents are nevertheless considered communicable by the Commission for Access to Administrative Documents (Cada). This independent authority is responsible for assessing whether an administration is supposed to publish a given document. Franceinfo had contacted it last fall, in order to have access to the health opinions issued between 2019 and 2023 by the ARS on swimming in the Seine. The verdict rendered in November had ruled in favor of franceinfo, and the ARS had complied with this decision by transmitting the requested opinions.

Their publication, last January, revealed that the ARS recommendations had not been respected during the tests carried out for the triathlon event, organized in August 2023. The athletes had been authorized to swim for two days, while the thresholds set by the Health Agency had been exceeded. Franceinfo had also revealed that deputies at the Paris city hall had participated in a swim in the Seine in July 2023, under the eyes of the mayor of Paris, despite an unfavorable opinion from the ARS on this event.

3 Because researchers and specialists cannot decide

In the absence of publication of water quality analyses, scientists themselves are unable to judge the state of the Seine since the beginning of the summer. Jean-Marie Mouchel, a researcher at Sorbonne University, explains that for the moment he can only rely on his own statistical models to measure the impact of the €1.4 billion bathing plan undertaken by the State and its local partners for the Games. “I am pretty much convinced that the number of days you can swim in the Seine will now be one day out of two, at certain sites”believes this eminent specialist. “But I’m saying that a bit haphazardly since I don’t have access to the data.”he immediately clarifies.

This expert in bacteriological analyses in the Seine has been part of a working group responsible for analyzing water quality data from the Parisian river on behalf of the State and City of Paris services for five years. “This allows us to have access to the data, but with a one-year gap. So the 2024 data, I will have it in 2025”he reports.

Other specialists are simply kept silent, accuses Mediapart. This is the case for the scientists and engineers who work at Eau de Paris, the municipal authority of the Parisian capital. It is the laboratories of this service that collect and analyze the water from the Seine. “But since the opening of the Olympic Games, the establishment has not dared to answer any questions about the state of the river.”writes the news site. This silence also concerns the staff of the city’s sanitation services. Also according to Mediapart, an email was sent to employees, asking them “the greatest discretion” when they exchange “on these subjects”including “in the personal sphere”. Questioned by franceinfo, the City of Paris declared that it is “It is quite normal for an organization to ask its agents or employees to direct any press requests to the department dedicated to this purpose”.

“Already in August 2023, communication was completely locked down during the ‘test events’ in the Seine. But now, it has been reinforced even more”judges Antton Rouget, one of the journalists who wrote the Mediapart investigation, interviewed by franceinfo. “The only people who are authorized to talk about the Seine are politicians or the organizers of the Games. And the media and citizens are asked to take their word for it.”regrets the journalist.