Andre Correa, Rio de Janeiro state's top environmental official, has acknowledged that Brazil's pledge of bringing down the levels of pollution flowing into the trash, raw sewage and debris-filled Guanabara Bay by 80 percent for the 2016 Summer Olympics is an unrealistic goal.

According to The Associated Press , Correa said he could not provide an estimate of how much officials would succeed in cutting the flow of pollutants into the bay where the Olympic sailing and wind surfing competitions are to be held.

Alastair Fox, head of competitions at the International Sailing Federation, voiced his concerns.

"The sailors and boats do not want to be in a field of play where there are any type of objects," he said according to BBC.

Brazilian media has claimed that the event could be moved to another sailing venue, but the Rio Olympics Organizing Committee said this was a no-go.

"The tests were positive, and we can confirm that water is safe for the athletes," said Rio-2016 Sustainability Manager Julie Duffus.

In August 2014, however, Brazilian officials were already dismissing the issue. They said recent tests showed that the waters in Guanabara Bay met international standards. This was announced after the first official test event for the sailing competitions had sailors bumping into floating debris, including sofas and even a dead dog.

In June, Mayor Eduardo Paes admitted the 80 percent target would not be met.

"I am sorry that we did not use the games to get Guanabara Bay completely clean," he said according to BBC. 

Greater Rio has a population of some 10 million people and millions of litres of untreated sewage are dumped in the bay every single day.

Environmentalists have been vocal about the slow slow progress in the water cleanup for years.