We’ve all been there: You’re innocently wading in the ocean when, all of a sudden, a wave rolls in and smacks you in the face. You swallow a bit of ocean water—and if you’re like me, you think nothing of it. That’s just part of the beachgoing experience: You get sunscreen in your eyes, sand collects in places you’d rather it didn’t, and you accidentally sip on salt water from time to time.
But one of these things is not like the others. According to a 2023 report from Environment America, a nonprofit that conducts environmental research, it’s probably a good idea to pay closer attention to the quality of the seawater you swim in—and, whenever possible, avoid gulping it down. Many beaches contain pretty high levels of bacteria and other pathogens that can make you sick. Of the 3,192 beaches scientists tested in 2022, 1,761 (or 55%) had potentially unsafe levels of fecal contamination on at least one of the days the water was tested, based on criteria from the Environmental Protection Agency (EPA). One in nine beaches met or exceeded that level on at least 25% of the days tested.
When it storms, rainwater pulls all sorts of muck, like Escherichia coli (E. coli) and Enterococcus, off the land and into the sea. Manure from farmland and sewage overflow seeps into oceans, filling our waters with bits of feces, Onema Adojoh, PhD, a visiting assistant professor in the department of earth, environment, and planetary sciences at Case Western Reserve University in Ohio, tells SELF. And coastal animals—seabirds like gulls, of course—deposit bacteria-packed droppings of their own in the water.
If you take a dip and are exposed to pathogens by ingesting them, inhaling them, or having direct contact through your eyes or an open wound, there’s a chance you could get sick with gastroenteritis (inflammation of the stomach and intestines that’s usually caused by bacteria or a virus), or a respiratory infection, or wind up with skin, ear, or eye irritation or infections. Any of those things can happen in a flash, even if you’re just cooling off for a sec: “When something is toxic or harmful, regardless of the quantity, it’s still going to have almost the same effects” if you’re exposed to it at all, Dr. Adojoh says.
How can fecal matter in seawater get you sick?
It’s impossible to list out all the microscopic pathogenic threats in the sea because there are so many and they’re always in flux due to factors like the season and local weather conditions. Per the new findings, seafaring fecal matter contains all kinds of gross little microorganisms. E. coli and Enterococcus are the biggies behind most swimming-associated gastrointestinal problems, like diarrhea, stomach cramps, nausea, and dehydration.
In 2022 alone, there were 8,788 beach advisories or closures in the US due to concerning levels of disease-causing pathogens. (These also include cyanobacteria from algal blooms, which can cause intestinal issues and neurological symptoms, and aquatic fungi like dermatophytes, which can cause nasty skin infections. Salmonella, which causes gastrointestinal infections, is also floating around out there, as are viruses like adenoviruses and norovirus and parasites like Giardia.) Waterborne illnesses are more common than you’d think: Every year, there are an estimated 29 million cases of illnesses people get after splashing around in oceans, lakes, ponds, and rivers.
