Research by the Fundação SOS Mata Atlântica in 2015 confirmed that every river in the City of Rio de Janeiro is polluted, including the Carioca River. The river, once the primary source of fresh water in the city, is now one of its most polluted. Untreated sewage is the primary source of pollution of the Carioca; the 7 kilometres (4.3 mi) stretch of the river in Guararapes and Cosme Velho are a great sources of unregulated sewage.