This Friday marks the opening ceremony for the 2016 Olympics in Rio de Janeiro, but what the athletes and onlookers may not know is just how dangerous and filthy the city’s surrounding water has become. A 16-month study by the Associated Press found water samples so badly contaminated that biomedical experts are advising Olympians: “don’t put your head underwater.” Ingesting just three teaspoons of the water could make someone violently ill and, in rare cases, lead to heart and brain inflammation.

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Raw sewage can be seen floating on Rio’s waters – and it’s absolutely teeming with bacteria and viruses that put the public at risk. The AP took adenovirus readings at the Rodrigo de Freitas Lagoon, where rowing events will take place. While adenovirus numbers in the thousands per liter would send a state like California into damage control mode, the Lagoon’s 248 million viruses per liter is making scientists’ heads spin. Even more shocking is the 1.7 billion viruses per liter that were collected in June of last year. Attempts to prevent raw sewage from reaching Gloria Marina were futile, as the numbers grew from 26 million per liter to 37 million in a little over a year. The situation is so bad that even the sand on beaches is contaminated.

Related: Anti-microbial suits will protect athletes from bacteria at the Rio Olympics

Some Olympic athletes have started taking antibiotics in preparation for the games, but this won’t protect them from viruses. Also, tourists who aren’t used to such high levels of pollution are at high risk from spending even one afternoon at the beach.

The local Olympics organizing committee spokesperson says athlete health is their “first priority,” yet the last year has shown the city has not done enough to make its beaches and waterways safe. Mario Moscatelli, a biologist who has flown a helicopter over the area monthly for 20 years stated, “The Guanabara Bay has been transformed into a latrine.”

Via Yahoo! Sports

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