It was supposed to be the Green Games for a Blue Planet. Instead, with five days to go before the Rio de Janeiro Olympics begin, it is clear that the city and state authorities have failed to comply with any of the ambitious environmental commitments they made when bidding for the event back in 2009.

"The environmental benefits were the most publicized and prioritized of the legacy promises," said David Zee, a professor of Oceanology at Rio de Janeiro State University. "In the end, they finished in last place."

The highest profile broken promise means large amounts of untreated sewage is still flowing into Guanabara Bay, where the Olympic sailing events will take place.

Olympic organizers had said 80 percent of the wastewater produced by the nine million people that live around the Bay would be treated by the time the Games started. Now officials admit that the new sewage treatment plants that have been installed will clean up only 48 percent of the waste. Some say the real figure is much lower than that.

A number of international sailors reported falling ill or suffering infections after entering the water several months ago, and stories of athletes feeling uncomfortable about competing in water that smells fetid continue today.

"They [athletes] should have complete confidence that Rio 2016 and the International Olympic Committee and the Brazilian authorities will put their health in first place," Richard Budgett, the head of the International Olympic Committee's medical team told reporters this week, seeking to allay their fears. "I am sure that the water will be of a good enough quality to ensure a safe competition."

The Rio Olympics have also been taken to task for not cleaning up the Jacarepagua Lagoon that surrounds the Olympic Park.

Plans to dredge the bottom of the lagoon were suspended for a period after Brazil's Federal Prosecutor identified irregularities in the tendering process and other procedural problems, such as the lack of an environmental impact study.

Then, last August, about a ton of dead fish had to be removed from the Lagoon. The fish reportedly died after strong winds disturbed decades worth of pollutants that released their toxins into the main body of water.

Zee, the biologist, emphasizes that while there are no Olympic events in the lagoon, it lies close to the Olympic Village where athletes are housed.

"The decomposition of the sewage and organic material can produce sulfide gas. Strong winds can disturb the bottom of the lagoon and give off this gas," he said. " It can cause nausea and headaches, if you're exposed to it for a long time."

Rio's authorities have also dropped the ball on a promise to plant 24 million seedlings to compensate for the carbon emissions caused by the Games. With just days to go, they have planted 5.5 million.

Rio's mayor, Eduardo Paes, has denied that the Olympics have failed to deliver an environmental legacy. He recently cited the controversial golf course, constructed in a protected area, as evidence of improvements.

Paes also hailed the unfinished sewage treatment work in Guanabara Bay as a relative success because sewage treatment had been improved from 15 percent to 50 percent, even if the 80 percent target was still far off. "That's an increase of 30 percent," he said. "You can't say that nothing has been done."

This was not enough to impress biologist Valerie Harwood who advised travellers "don't put your heads underwater" after being shown the results of a study of the water commissioned by the Associated Press.

"Seeing that level of pathogenic virus is pretty much unheard of in surface waters in the US, she told the agency in a story published this week. "You would never ever see these levels because we treat our wastewater."

Rio 2016's inability to deliver on its environmental pledges is reminiscent of the broken promises also left by Brazil's 2014 World Cup. According to the National Association of Urban Transport Companies, only 18 percent of 125 urban mobility projects promised for the tournament are currently in operation.

It also echoes the disappointments of other Olympics.

The London 2012 Games did reduce emissions during construction work and improved the city's public transit network. Even so, a joint WWF-UK/BioRegional report criticized the event's inability to meet its renewable energy targets. Environmentalists have also alleged that construction work at the 2014 Winter Olympics in Sochi, Russia, have seriously damaged the region's natural ecosystems.

It is also true that Rio's Olympics have brought some improvements in public transportation — even if the extension of the city's westbound metro line inaugurated last week will only be open to athletes, Olympic workers, and spectators during the event itself. But it is now indisputable that the Rio Games are immeasurably far from fulfilling those first grandiose environmental pledges.

"These days, Olympic bids come chock full of so-called legacy projects that gleam green," Jules Boykoff, author of Power Games: A Political History of the Olympics. "But Rio 2016 is in the running for the most greenwashed Games ever."