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RIO DE JANEIRO, BRAZIL - JULY 18: A boy reaches for a ball along a polluted canal in the Mare favela community complex on July 18, 2016 in Rio de Janeiro, Brazil. Polluted canals in Rio such as this one empty in Guanabara Bay. The Mare complex is one of the largest favela complexes in Rio and is challenged by violence, pollution and poverty. The Rio 2016 Olympic Games begin August 5. (Photo by Mario Tama/Getty Images)

RIO DE JANEIRO, BRAZIL - JULY 18:  A boy reaches for a ball along a polluted canal in the Mare favela community complex on July 18, 2016 in Rio de Janeiro, Brazil. Polluted canals in Rio such as this one empty in Guanabara Bay. The Mare complex is one of the largest favela complexes in Rio and is challenged by violence, pollution and poverty. The Rio 2016 Olympic Games begin August 5.  (Photo by Mario Tama/Getty Images)