(CNN) Just days left until the Games start, studies have found the waters on which some of the world's best sailors will compete are contaminated by viruses and drug-resistant superbugs.
Scientists at the Federal University of Rio de Janeiro carried out tests in areas including Guanabara Bay — the sailing venue — over the course of a year.
They told CNN they had found the highest level of superbugs of the sort found in hospitals on the shores of the bay, with pollution problems also evident on tourist beaches.
"We believe hospital sewage gets into the municipal sewage and then gets to Guanabara Bay and finally to the beach," Renata Picao, a professor at the university, explained.
Water pollution in Guanabara Bay has been a problem for decades because of limited sanitation and sewage treatment facilities in Rio and the surrounding areas.
Spanish sailor Fernando Echavarri told CNN the waters were the dirtiest he had competed in and warned: "As soon as you cut your foot you can easily infect yourself — and that is a problem."
However, Josh Adams, the managing director of U.S. Sailing, told CNN his team had trained extensively in Guanabara Bay "with no major incident."
Australian Chef de Mission Kitty Chiller has also addressed the water quality in Rio and said the team's athletes were "getting on" with their training while taking precautionary measures such as good hygiene and probiotics.
"At this point in time, we ain't going to change the water quality in the next week so they'll just get in and do their best," Chiller told reporters.
Authorities in Rio insist there is an "internationally acceptable" level of bacteria in the water.
"We would never risk the health or condition of any athlete for a competition," Mario Andrada, chief spokesman for the local Olympic organizing committee, told the Associated Press.
"So the health of the athletes is our first priority, and the athletes don't run a risk sailing in Guanabara Bay."
However speaking to CNN in June, scientist Mario Moscatelli claimed the waters in and around the bay were "dangerous."
"All the sewage, all the trash, when the tide is low, floods in that direction," he added, pointing from a tributary in the direction of Rio.
"If you have the low tide, rain and wind inside to outside Guanabara Bay, then we have a big problem."
Plans to revamp Rio's infrastructure, including massively upgrading its sewage and water-cleaning capabilities, have been dented by the economic downtown that has affected Brazil since the Games were awarded.
Contingency plans could include changing the times of sailing events — pollution is worst in the mornings — or the location of the launch area.
"Athlete safety is our priority," Tania Braga, the head of Sustainability and Legacy at Rio, told CNN.
"We are going to do daily tests during the games and we do not expect to have any problems of non-conformity in the race areas, but we are prepared with contingency measures if needed."