A dip in the ocean may be among the best ways to cool down in the summer. But sea waters can also be hot spots for fecal contamination.

In a new report from Environment America, researchers compared water testing results from more than 3,000 beaches in the United States and found that, on at least one testing day, more than 50% of beaches contained unsafe bacteria levels of fecal indicator bacteria. About 1/9 of beaches contained unsafe levels of fecal indicator bacteria for at least 25% of testing days.

Environment America. Safe for Swimming? July 5, 2023.

 

 

Fecal indicator bacteria include bacteria like E.coli and Enterococcus, which can pass from person to person through fecal matter (including when people don’t wash their hands after going to the bathroom) and put people at risk for adverse health conditions like gastrointestinal issues and respiratory conditions.

Environment America. Safe for Swimming? July 5, 2023.

Wade TJ, Arnold BF, Schiff K, et al. Health risks to children from exposure to fecally-contaminated recreational water. PLOS ONE. 2022;17(4). doi:10.1371/journal.pone.0266749

 

The organization based its standards for safe and unsafe levels on the Environmental Protection Agency’s (EPA) most protective Beach Action Value (BAV), which is a “conservative, precautionary tool” created by the EPA to help states regulate beach safety. The BAV for used E.coli was 190 colony-forming units per 100 milliliters (cfu/100mL) for freshwater, and the BAV used for Enterococcus was 60 cfu/100mL for marine and freshwater.

Environment America. Safe for Swimming? July 5, 2023.

 

States are not legally required to maintain the EPA’s BAV standards, but those that adopt their own standards must still receive EPA approval for their decision. States can modify criteria to fit the specific needs of a location or adopt other, science-backed criteria that are just as protective as the EPA standards, according to the EPA.

United States Environmental Protection Agency. Final Water Quality Standards Bacteria Rule for Coastal and Great Lakes Recreation Waters.

 

According to various studies cited by the EPA in their second five-year review of water safety criteria, published in 2023, feces in the water—particularly human feces—is no small deal. Human feces in water has been linked to norovirus and other diseases and poses higher risks to people than non-human feces sources, according to the EPA. (The Environment America report did not separate for human versus nonhuman fecal pathogens.)

United States Environmental Protection Agency. Final Water Quality Standards Bacteria Rule for Coastal and Great Lakes Recreation Waters.

 

 

What else is in the sea?

 

Unfortunately, fecal pathogens aren’t the only dangerous stowaways in the sea. The EPA assesses waters for various risks (34 benchmarks) or “impairments,” including contamination pathogens, pesticides, trash, algae, mercury, and others. You can search the safety of waterways near you by inputting your area or the location you are interested in on an EPA search tool. This will tell you about the water quality concerning human health, aquatic life, eating fish, and drinking water.

 

Can salt water disinfect?

 

In highly concentrated forms, salt water—or saline—can be a disinfectant; this isn’t necessarily the case with the ocean, which is less concentrated and full of those other nasty pathogens.

 

Ocean risks ebb and flow

 

The report reveals unsettling information about the safety of our seas. But oceans aren’t all bad, all the time. One silver lining to the findings is how frequently water levels changed from safe to unsafe levels. This reinforces that the composition of ocean waters is constantly changing and fluctuating as the water flows from place to place. (Although this also means it can be hard to predict if we swim on a healthy or toxic water day).