RIO DE JANEIRO: The World Rowing Federation (FISA) gave a thumbs-up to Rio de Janeiro's much questioned water quality on Tuesday, with a report saying incidences of illness were much lower at the recent world junior championships than in previous years.

The FISA sports medicine commission surveyed the 54 national federations who took part in the August event at the Lagoa Rodrigo de Freitas, the same inner city lagoon where Olympic rowing events will be held next year.

"Forty national federations reported no illness among their team members during or after the event; 13 reported one to five cases of illness; and one team reported more than five cases of illness," FISA said in a statement.

"Whenever a group travels together to another country, there is always a higher risk of illness," FISA executive director Matt Smith added.

"This can be for a variety of reasons including new foods being consumed, the impact of long-haul flights as well as the affect of new surroundings and travelling with a large number of people. The level of illness at the Rio junior championships was lower than at many other junior championships."

The issue of water quality has plagued Rio as it prepares to become the first South American city to host an Olympic Games.

The city promised to cut the amount of raw sewage flowing into the bay where the sailing and open water swimming events will take place by 80 percent but has since admitted it will not meet that target.

An independent report issued this year found levels of disease-causing viruses were as much as 1.7 million times the level that would be considered hazardous on a Southern California beach.

There were also fears for the lagoon, which is fed by the small and often filthy rivers that run down Rio's hillsides.

However, FISA said the water quality was "very acceptable" and expressed satisfaction that "the results showed that incidences of illness were much lower than compared to prior years' events."