The pre-Olympics swimming test competition due to take place Sunday in the Seine in Paris has been cancelled due to pollution of the river, the international swimming federation said after analysis of the latest water samples.
Following recent heavy rainfall, "water quality in the Seine has remained below acceptable standards for safeguarding swimmers' health," World Aquatics said in a statement on Sunday.
"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."
Friday's training had already been cancelled and the women's race was postponed from Saturday to Sunday in the hope the water quality would improve.
Heavy rains for the past week in Paris have caused sewers to overflow, polluting the Seine.
"World Aquatics is disappointed that water quality in the Seine has resulted in the cancellation of the World Aquatics Open Water Swimming World Cup, but the health of our athletes must always be our top priority," said World Aquatics president Husain Al Musallam.
The federation said it "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".
"World Aquatics remains excited at the prospect of city-centre Olympic racing for the world's best open water swimmers next summer," it said.
The events are also a prelude to the future return of swimming in the Seine promised by Paris Mayor Anne Hidalgo from 2025 on three sites where swimming has been prohibited since 1923.
Olympic open water swimming has frequently been hit by pollution concerns.
At the end of the test event in 2019 ahead of the Tokyo Olympics, swimmers protested against the quality of the water in Tokyo Bay.
At the Rio Olympics in 2016, the prospect of swimming in Guanabara Bay, also very polluted, also made headlines.
