Water pollution concerns in the Odaiba area have grown after a Tokyo 2020 survey revealed the quality was not good enough to meet International Swimming Federation (FINA) and International Triathlon Union (ITU) standards.
Tokyo 2020 and the Metropolitan Government conducted a water quality assessment in Tokyo Bay, the location of the marathon swimming and swimming leg of the triathlon, to mirror the 21 days of competition at the Olympics and the five days of action at the Paralympics.
It revealed the quality of the water only matched FINA standards on 10 days and adhered to ITU regulations on six days.
International Olympic Committee (IOC) Coordination Commission chairman John Coates, speaking following the conclusion of the two-day Project Review visit to the Japanese capital, admitted the readings resulting from the survey were "were not what they should be".
"FINA took note today of the Tokyo 2020 announcement of the water quality test results in Odaiba," FINA said in a statement.
Tokyo 2020 have vowed to implement water quality improvement measures in the lead-up to the Games to ensure that the venue "satisfies all relevant International Federation standards".
In a statement in response to the results, Tokyo 2020 have also promised to "consider all necessary measures to ensure the smooth operation of events at Odaiba Marine Park, including amendments to event dates and/or times in response to weather conditions".
"In August 2017, there was rainfall in the Tokyo area on 21 consecutive days, the second highest number of consecutive days of rain recorded in August since 1977," the statement added.
Tokyo 2020 have also defended the quality of the water at the Odaiba Marine Park, highlighting major events in marathon swimming and triathlon have been held there in the past.
The venue has hosted Japan’s National Triathlon Championships for more than 20 years, while Japan Swimming Federation staged its Tokyo Marathon Swimming events there between 2009 and 2013.