When I look ahead to the upcoming summer Olympic Games in Rio, the first thing that comes to mind is the abysmal water quality, and how athletes are expected to swim, sail, and compete in water that could severely endanger their health.

Recent news stories about Rio’s water quality, which shows widespread elevated levels of viruses and bacteria from along the coastline to far offshore, have got much of the world thinking about water quality – not only in Rio, but in their own watershed.

Polluted water in Rio. Photo by MAHM on Flickr.

It’s spurred a lot of Swim Guide users to ask: what do they really test for at my favourite watershed?

Of course, each local monitoring authority may have somewhat different standards (so long as they’re at least as good as federal guidelines), but there are general guidelines followed.

What Is Tested For – And What Isn’t?

Currently, the basis for global guidelines is to use standard bacterial indicators including E. coli, fecal coliforms, and enterococci.1 If these indicators are found at high levels in the water, human sewage is assumed to be present and risk of contracting an illness (including a virus) goes up.

Canadian guidelines don’t require that lakes (or beaches) be routinely tested for viruses, and this is similar around the developed world.


Bacterial indicators are often sufficient to point to the presence of viral contaminants. But testing for viruses is also a complicated process: there aren’t a set of standardized guidelines for testing and results can be difficult to interpret.

Should I Be Worried about Water Quality?

The most frequent negative health effects of swimming in contaminated recreational water is enteric illness, which generally leads to nausea and vomiting, abdominal pain, and diarrhea. Common illnesses caused by waterborne viruses include Rotavirus, Adenovirus, Norwalk, and Hepatitis A.

However, it’s always best to err on the side of caution. Avoid recreational water activities for at least 48 hours after a heavy rain or snowmelt. Avoid outfalls and stagnant bodies of water. Always wash with soap and water after swimming or coming into contact with water. And check Swim Guide before you head to the beach.

You can learn more about your local watershed by visiting your favourite beach in Swim Guide, where we show what is tested for and your local standards, or your local water quality monitoring authority’s website.


World Health Organization (WHO). 2015. Water quality for the Olympic Games in Rio De Janeiro, 2016. Water Sanitation Health. Retrieved from: http://www.who.int/water_sanitation_health/bathing/statement-rio-water-quality/en/.

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