As part of a wide-ranging progress report here this afternoon, during which he was also forced to provide several reassurances about the new subway line due to connect the main Olympic Cluster in Barra de Tijuca with the city centre, Nuzman anticipated pollution-related questions by outlining steps being taken at the beginning of his report.

This included an update on German sailor Erik Heil, one of several taken ill with infections after competing at last month's test event, and is now back at home recovering and reportedly ready to resume training "within the next few days".

With 15 members of the US rowing team having also been taken ill after their test event on the Lagoa Rodrigo de Freitas, and an Associated Press investigation finding a "major risk" of athletes contracting viruses during the Games, the issue has become a major challenge.

International Sailing Federation chief executive Peter Sowrey has revealed they are still considering moving the venue further out into the Atlantic in order to ensure cleaner water, but organisers are keen to avoid this happening due to a desire to keep the event close to the shore and within site of some of the host city's most picturesque landmarks.

"This is a very serious matter and we are doing our absolute best to protect people's health," said Nuzman.

"It needs improvement, but it will be totally clear by the end of the year.

"We ask you not to give up on Guanabara Bay, as the awareness generated is vital to its future."

When pushed to give a guarantee that not a single athlete would become ill due to the water quality, he added: "The health of the athletes is our number one priority, and we are working closely with the State Government to achieve this.

"I have no doubt we will do this.

"I can guarantee we will work every day, we won't have any problems."

Reducing levels of pollution by 80 per cent in the Bay, a problem in Brazil for decades, was billed as a major legacy objective for Rio de Janeiro during the city's successful bid for the Games over Madrid, Chicago and Tokyo in 2009.

Although officials claim it has already been reduced by 50 per cent, many experts are are skeptical of this figure and see little or no improvement.

Many will also be unconvinced by Nuzman's assurances today, due to the lack of apparent progress following past claims, with one of the courses on the Bay even having to be closed during the test event due to the large amount of rubbish blocking the path of the boats.

Nuzman, also President of the Brazilian Olympic Committee, also claimed the subway line due to link Barra - the main venue site as well as the location for the Athletes' Village, Media Centre and International Olympic Committee (IOC) hotel - with Copacabana and the centre of the city, will be completed by "May or June" next year.

This follows an auditors report in Brazil in July suggesting there is a "high risk" of it not being ready in time.

Work is currently 75 per cent finished, Nuzman claimed, claiming this included many of the most difficult aspects.

With more than 300,000 people due to travel on the subway on each day of the Olympics, its completion is vital to the success of the Games, particularly because the one road currently in place is already a huge bottleneck at rush hour times, especially in a narrow tunneled section.

Nuzman, speaking following a hectic summer which included presentations at both the Pan American Sports Organization General Assembly in Toronto and the IOC Session in Kuala Lumpur before last month's latest IOC Coordination Commission inspection, was also optimistic about ticket sales and the proposed budget for the Games. 

He claimed the Olympics and Paralympics is a ray of light for Brazil in a time of widespread economic and political misery and that, through projects such as the second major venues cluster in the impoverished Deodoro neighbourhood, they are using the Games to bring new opportunities to many people.

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