08-05-2025
There's Fecal Matter in Our Drinking Water — Here's What Scientists Are Doing About It
Researchers have developed a more precise method for detecting fecal contamination in water using viral DNA markers, allowing them to trace even low-level pollution and identify whether it's from humans, animals, or multiple sources.
Traditional methods, like fecal indicator bacteria (FIB) testing, are limited because they only detect high levels of contamination and don't reveal the source, whereas the newer microbial source tracking (MST) technique is more detailed, cost-effective, and better suited for current climate challenges.
Fecal contamination is a widespread and serious global issue, affecting nearly 2 billion people, and this improved testing could help public health officials respond faster and more accurately to threats, especially as aging infrastructure and climate-driven flooding increase have found a new way to test for water contamination. And it's thanks to our poop.
In late 2024, researchers from Chungnam National University and Gyeongsang National University published their findings on a new technique for detecting fecal contamination in water using human viral DNA, known as microbial source tracking (MST), in the journal Water Research.
And while this may make you let out a little "ew" under your breath, it's critical to know that fecal contamination is, in fact, a significant issue both globally and here in the United States. The World Health Organization explained, "In 2022, globally, at least 1.7 billion people use a drinking water source contaminated with feces. Microbial contamination of drinking-water as a result of contamination with faeces poses the greatest risk to drinking-water safety."
And as noted in a 2020 study published in the journal Current Environmental Health Reports, "Aging sewer infrastructure in the USA and elsewhere will require rapid methods to assess fecal contamination of water. The number of extreme weather events, including flooding events, is forecasted to increase with climate change and has been associated with contamination of water resources."
Related: Your Cutting Board May Have 200 Times More Fecal Bacteria Than a Toilet Seat
Runoff contamination can transfer harmful bacteria to humans, such as E. coli, leading to various health concerns. Therefore, recognizing fecal contamination in the water supply is crucial for your health. Thankfully, scientists are on the case.
As Food Safety explained, conventional testing involved sampling water by adding droplets to a microbial culture (known as fecal indicator bacteria or FIB). Although this method is both cheap and easy, it can only detect fecal matter at higher contamination levels.
However, a viral-DNA method employs microbial source tracking (MST), which can detect biomarkers of fecal matter at much lower levels. While the MST method itself isn't new — it's been around for roughly two decades — the real breakthrough is these researchers' deployment of human-specific crAss-like phage DNA markers, which is a really fancy way of saying they can now spot smaller traces of fecal matter and identify if it's human waste far more precisely than before. It can even detect where the fecal matter originated — i.e., if it's human or animal — or identify multiple sources at once.
A 2024 study published in the journal Science of the Total Environment examined this updated MST method by "investigating the abundance, sources, and potential causes of fecal contamination" across three marine and seven freshwater stations in Vaughn Bay, Washington. This research included tests conducted in a shellfish growing district during both "base- and storm-flow events."
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This research team evaluated the old-school FIB method, along with optical brightener assessment (a fluorescent compound that indicates fecal contamination), and the newer MST method, the last of which "targeted a broad range of hosts including, such as humans, birds, cows, horses, ruminants, dogs, and pigs, with sequencing-based MST in identifying fecal contamination sources."
After testing the waters, they identified a few critical points. First, birds and humans are the primary culprits of contamination; second, stormwater runoff exacerbates contamination significantly; and third, the sequencing-based MST provides the most effective testing approach. The researchers noted that this method is more cost-effective per sample and yields much more detailed information, which is why they now recommend its use to officials.
But here's a little other fun fact for you: Fecal contamination doesn't just happen in our waterways. As the Washington Post explained in 2023, there's fecal contamination on essentially everything.
The paper pointed to a 2012 study that tested 85 grocery carts and found that 72% of them tested positive for fecal bacteria. Another 2017 study looked at "microbial contamination" in home kitchens, including fecal coliforms. It found fecal coliforms in 44% of homes, "most often in samples from kitchen sinks, sponges, and dishcloths," and E. coli in 15% of homes, "mostly in samples from kitchen sinks." So, go ahead and wash your hands right now. And be grateful for scientists who help us keep our waterways safe.
Read the original article on Food & Wine
