As soon as I stepped out of Galeão International Airport, the stench hit me. Not the stench of political corruption — though Brazil has plenty of that to go around — but a bad smell like an open sewer.

And that is, in fact, what Rio’s Guanabara Bay is. Green soda bottles, plastic bags and rat carcasses float atop the brown, sludgy water. Beneath lurks a toxic cocktail of viruses and drug-resistant bacteria. Several sites for Olympic water events are awash with sewage: Every day, some 169 million gallons of untreated human waste flows into the bay, where Olympic sailing and windsurfing will be staged.

As the Games approach, the focus has been on how the polluted water could affect Olympic athletes. This overlooks the harm imposed every day on the city’s residents, known as Cariocas. For them, the water is a long-term health catastrophe.

It didn’t have to be this way. Rio boasts a rich history of environmentalism, having hosted the United Nations’ Earth Summit meeting in 1992 and the Rio+20 conference in 2012. The city’s Olympic bid elevated public expectations, with organizers promising to deliver major improvements in air and water quality.

But the gulf between aspiration and actuality is vast. The bid documents implied that more than 80 percent of sewage at Guanabara Bay would be collected and treated by 2016. But state officials recently pushed back the cleanup deadline to 2035.

An investigative report by The Associated Press and the virologist Fernando Spilki of Brazil’s Feevale University found that Olympic water venues were badly contaminated. Ingesting even three teaspoons of water meant a 99 percent chance of infection by virus (though because of varying levels of immunity in the population, not everyone would necessarily fall ill).

The sailors, swimmers and rowers would be susceptible to “respiratory and digestive illnesses, including explosive diarrhea and vomiting,” which could result in acute diseases of the brain and heart, the report found. Athletes would also face a risk of contracting hepatitis A.

I asked Brad Brooks, The Associated Press’s former bureau chief in Rio, what grade he would assign the water cleanup efforts. “I would give them an F,” he said without hesitation. “What’s happening here is an environmental crime. And they’re holding the Olympics in it.”

This crime will affect the cariocas long after the Olympic juggernaut rumbles out of town. Unlike athletes who will compete in the water with all manner of high-tech protection at their disposal, city residents use these waters without such safeguards day in and day out.

The consequences are harsh. In the short term, gastrointestinal problems, persistent skin infections, even serious heart problems are commonplace. Doctors in Rio’s favelas, or poor neighborhoods, calculate that up to 40 percent of their patients’ illnesses result from contact with untreated sewage.

The problem of underinvestment in water and sewage treatment is nationwide: Across Brazil, roughly two-thirds of hospitalizations are attributed to waterborne diseases. Younger children are especially vulnerable until their bodies have developed enough antibodies. The medical journal The Lancet reported that for Brazilian children under 5, diarrhea diseases are the second-leading cause of death, killing more infants every day than AIDS, malaria and measles combined.

In the longer run, chronic water-induced illness results in missed days of school, which in turn causes students to lag behind in their education and intellectual development. One Brazil-based researcher reportedthat children who grow up without a proper sewage system earn about 10 percent less than their peers from a similar socioeconomic background who have basic sanitation.
Then there are the “superbacteria,” opportunistic pathogens that can erupt as infections in the blood, lungs, intestines and urinary tract. According to the Centers for Disease Control and Prevention, these antibiotic-resistant bacteria can result in death in up to half of cases of infection. Even Ipanema and Leblon — two of Rio’s most famous tourist beaches — have tested positive for these superbugs at least half the time.

The Olympics were supposed to change all this. And a program called Morar Carioca, or Carioca Living, was to be the means to achieve that change. The plan involved upgrading favelas with sewer systems, reliable water, paved roads and improved street lighting.

Eduardo Paes, the English-speaking mayor of Rio who will be the political face of the Games next month, initially trumpeted the program. In 2010, he said that thanks to “Olympic inspiration,” Morar Carioca would be a key legacy of the Games. In a TED talk, he vowed to have all favelas “completely urbanized” by 2020.
But after Mr. Paes was re-elected in 2012, he canceled Morar Carioca’s commitment to consultation with local communities and inexplicably voided contracts with architecture firms. Starved of funds, the program stumbles along. In 2014, Mr. Paes claimed that Morar Carioca was not even part of the Olympic legacy, which reinforced his critics’ view that his former support for the project had merely been an election ploy.

With opening ceremony of the Rio Games just days away, it’s time to revive the original, cooperative spirit of the Morar Carioca plan. Mr. Paes boasts that Rio is in good financial shape despite the expense of preparing for the Olympics, but Rio de Janeiro State, which is responsible for water cleanup, recently declared a “state of public calamity” in an effort to wring out more money from the federal government.

The mayor himself calls the failure to clean up Guanabara Bay “a missed opportunity.” But if Rio’s Olympic legacy is to mean anything, it must benefit the ordinary people of the host city who have made big sacrifices to stage a lavish sports festival for the world’s top athletes. The home team deserves a win, too.

Jules Boykoff, a professor of political science at Pacific University, is the author, most recently, of “Power Games: A Political History of the Olympics.”

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