Concerns have been raised before the men’s and women’s Boat Races between Oxford University and Cambridge University on Sunday after testing found high levels of the bacteria E. coli in the River Thames.
The Boat Race, which was first staged in 1829, is a rowing event which takes place every year between students from two of the UK’s elite universities over a 4.25-mile stretch of the Thames in west London.
Testing by the environmental campaign group River Action discovered high levels of the potentially harmful bacteria E. coli throughout the stretch of water which will host the latest edition of the Boat Race this weekend.
In a statement on Wednesday, River Action warned that the Thames would be classified as ‘poor’ under environmental regulations if it were designated as a ‘bathing water’ site.
Despite minimal rain — which can lead to water companies releasing untreated effluent into the rivers to avoid sewage overflows — since River Action began testing for E. coli on March 10, almost 30 per cent of samples exceeded safe limits for entering the water, almost three times the threshold for bathing waters rated ‘poor’.
A total of 41 samples were taken at key points between the start of the Boat Race course in Putney and the finish at Chiswick Bridge, where the highest reading — 2,267 CFU/100ml (colony-forming units), more than twice the Environment Agency and World Health Organisation thresholds for safe recreation — was recorded. This is the point at which the winning Boat Race cox is traditionally thrown into the river.
“It’s a real worry that in 2025, unsafe water quality in the Thames is still a concern,” five-time Olympic gold medal-winning British rower Sir Steve Redgrave said in a news release. “Rowers, river users, and the public deserve better.”
Imogen Grant, who won gold for Team GB in the lightweight women’s double sculls at the 2024 Paris Olympics and is a three-time Boat Race winner with Cambridge, highlighted health concerns.
“As rowers, we train on these waters every day, and the health and climate risks are deeply concerning,” she said in the release. “It’s unacceptable that we have to compete on a river with such an unavoidable threat to health.”
Treated wastewater from sewage treatment plants currently face no legal limits on E. coli levels, while storm overflows are only permitted during “exceptional circumstances”, typically during heavy or sustained rainfall that risks overwhelming the sewer system.
“Right now, if the stretch of the Thames used for the Boat Race were an official bathing site it would be graded poor, the lowest possible rating,” said River Action’s Head of Communities, Erica Popplewell. “The government’s own advice for such water is ‘do not swim.’ We strongly suggest that the winning team on Sunday think twice before throwing their cox in the Thames.
“We would also urge all rowers to follow the ‘Guidance for Rowing When Water Quality is Poor’ safety guidelines to mitigate risk. The Boat Race should be about sporting excellence—not about worrying if you’ll get sick from being dunked – and attracting people to take up water sports as a healthy activity.”
At the Paris Olympics in 2024, the water quality in the river Seine, where the swimming part of the triathlon took place, was deemed to be unsafe before organisers considered it of sufficient quality for the event to take place as originally planned.
The women’s triathlon eventually took place at the Seine last summer despite water quality concerns (Ezra Shaw/Getty Images)
There had been pre-Games investment of more than £1.2billion (€1.4bn) to clean up the river, but levels of E. coli and other bacteria in the water spiked to dangerous levels following heavy rainfall in the build-up to the event.
Paris’ combined sewer system, which sees both wastewater and stormwater travel through the same pipes, means large quantities of rain can make pipes exceed capacity, with untreated wastewater overflowing into the Seine.
It had led to concerns that the triathlon might become a duathlon and fears over athletes’ health but the events were still held in full.
There has been controversy already before this year’s Boat Race over the eligibility of certain students which has been labelled “a desperate ploy … to gain an upper hand in the most slimy way”.
The row stems from the banning of students undertaking a Postgraduate Certificate in Education (PGCE) course — combining academic study of teaching with practical experience — from being able to compete. Such students had previously been permitted to participate.
Cambridge has won five of the past six men’s races and each of the past seven women’s races, emerging victorious in both last year.
When approached for comment, Thames Water — the private company responsible for the water supply and waste treatment in London — pointed to a separate study from Fulham Reach Boat club which had the E. coli threshold at ‘excellent’ in March.
“The boat race route is not a bathing water area and so we are not funded to routinely disinfect or sterilise final effluent,” the statement added. “In addition, The Thames Tideway Tunnel has prevented 6,376,450M³ of sewage from entering the tidal Thames since it was connected earlier this year and will reduce the volume of discharges entering the tidal Thames in a typical year by 95 per cent.”
The Boat Race Company, which organises the event, said it “recognises the work that groups such as River Action are doing to raise awareness and campaigning to clear up the rivers”.
“Water quality remains an ongoing concern for The Boat Race, and we will continue to follow British Rowing’s Poor Water Quality Guidance to protect the health of our student athletes,” a statement added. “This includes the covering up of open wounds, regular handwashing, showering as soon as possible after coming off the water, and highlighting the risks of entering the water.
“Clearly, the water quality testing carried out along the River Thames shows there is more work to be done to get our waterways where we all want them to be, but we are very encouraged to see the Tideway Tunnel fully operational which we hope will have a transformative effect on cleaning up the Thames.”
(Henry Nicholls/AFP via Getty Images)