The Water Quality in Guanabara Bay is far more a function of the sewage of Rio de Janeiro than it is from a 10 year old minor oil spill.
http://www.cibg.rj.gov.br/qualidadedaagua/sessao.asp?cod_secao=bacia_guanabara&lng=
Thank you.
Just a quick search and I discovered the same thing.
Pollution is nothing new to Rio de Janeiro, but environmentalists say many of the city’s waterways now represent a grave threat to public health and Rio’s tourism industry.
In January a stretch of the Barra da Tijuca beach was cordoned off after toxic algae appeared in the water, and at the end of March authorities removed a tonne of dead fish from the Guanabara bay.
Dark stains known as “black tongues” periodically appear on Rio’s beaches, and strips of white and yellow foam - the result of untreated sewage, environmentalists say - have started to show up off the upmarket beach neighbourhood of Leblon. After a large crimson stain appeared at Leblon government officials claimed the “red tide” was the product of harmless algae. Environmentalists are unconvinced.
http://www.guardian.co.uk/environment/2007/apr/28/brazil.pollution