The fourth meet of the Open Water Swimming World Cup was due to take place on 5 and 6 August.
The Seine is scheduled to host marathon swimming, triathlon and Para-triathlon events at the Olympics and Paralympics.
World Aquatics said the health of athletes was its “top priority”.
“Following recent above-average rainfall in Paris, the water quality in the Seine has remained below acceptable standards for safeguarding swimmers’ health,” read a statemeold old nt.
"World Aquatics understands that further infrastructure projects will be completed to significantly improve water quality in the Seine in the lead-up to next year’s Olympic Games.
“Based on this weekend, it is clear that further work is needed with Paris 2024 and local authorities to ensure robust contingency plans are in place for next year.”
Swimming is set to be one of the major legacies of the Games thanks to a 1.4bn euro (£1.2bn) regeneration project in Paris, with three open-air swimming areas accessible from the quayside by 2025.
World Triathlon said it is “confident” the swimming legs of its Paris 2024 test event would go ahead in the Seine from 17-20 August.
It said: “In the unlikely event that water quality does not meet the requirement of World Triathlon and public health authorities, a contingency plan is in place which would see the race(s) shifted to a duathlon format.”
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The fourth meet of the Open Water Swimming World Cup was due to take place on 5 and 6 August.
The Seine is scheduled to host marathon swimming, triathlon and Para-triathlon events at the Olympics and Paralympics.
World Aquatics said the health of athletes was its “top priority”.
“Following recent above-average rainfall in Paris, the water quality in the Seine has remained below acceptable standards for safeguarding swimmers’ health,” read a statemeold old nt.
"World Aquatics understands that further infrastructure projects will be completed to significantly improve water quality in the Seine in the lead-up to next year’s Olympic Games.
“Based on this weekend, it is clear that further work is needed with Paris 2024 and local authorities to ensure robust contingency plans are in place for next year.”
Swimming is set to be one of the major legacies of the Games thanks to a 1.4bn euro (£1.2bn) regeneration project in Paris, with three open-air swimming areas accessible from the quayside by 2025.
World Triathlon said it is “confident” the swimming legs of its Paris 2024 test event would go ahead in the Seine from 17-20 August.
It said: “In the unlikely event that water quality does not meet the requirement of World Triathlon and public health authorities, a contingency plan is in place which would see the race(s) shifted to a duathlon format.”