5 things to know about filthy water awaiting Rio Olympians

In this July 28, 2015 photo, workers remove garbage collected by floating waste barriers in a canal at the Mare slum complex, in Rio de Janeiro, Brazil. Rio's historic sewage problem spiraled over the past decade as the population exploded with many of the metropolitan area's 12 million residents settling in the vast slums that ring the bay. Waste flows into over 50 streams that empty into the once-crystalline Guanabara Bay. AP/Silvia Izquierdo