Quite correct NPF.

Moderate to heavy rainfall runoff will produce this, independent of sewage pretreatment systems in place. This is a condition world wide, and found today in the US, even in California and Hawaii.

For an example, Aliso Beach in South Laguna, California, continues to experience rainfall run off contaminantion, or " pluvial " conditions , when heavy rainfall occurs there. After one week of normal tidal action ( an agitated cleansing and dispersal ), the sand and water usually return to a safe level for beach activities.

I prefer to body surf, kiteboard, and just swim at Porto Das Dunas beach in Fortaleza, but I would have no problem at Arpoador, Leme, Copacabana, or any of the other major beaches in Rio under normal conditions. When I travel there, I do. If the warnings are up, and contaminant signs posted, then I would take precautions just as I would elsewhere in the world.

When we did our study in 1971, the outfall into Guanabara Bay and the surrounding beaches was quite raw, two days per week. Today, those outfalls are long closed, and multiple pretreatment systems are in place and functioning for Rio.