Crowds flocking to rivers and streams over Labor Day weekend are doing more than just cooling off and having fun; they’re temporarily introducing chemicals and microscopic organisms into their local waterways, according to a new study from Johns Hopkins University.
The study published today ACS ES&T Wateris the first holistic assessment of the impacts of recreational activities on water bodies. The results also shed light on the compounds and chemicals people splash around in when their favorite swimming spots are crowded.
“People are exposed to different chemicals because of the choices of their fellow swimmers. And everyone is swimming around in them like in soup.”
Carsten Prasse
Assistant Professor, Whiting School of Engineering
“Residues from sunscreens, shampoos and other chemicals you use around the house can wash into the water. And the same goes for the person next to you,” said lead author Carsten Prasse, assistant professor of environmental health and engineering at Johns Hopkins University. “People are exposed to other chemicals because of the choices of their fellow swimmers. And you’re all swimming in that like a soup.”
Prasse and his team collected water samples from Clear Creek—a popular tubing spot for locals in Golden, Colorado—over Labor Day weekend 2022. One collection point was upstream from recreational activities and the other was downstream where people exit the water.
Using analytical chemistry techniques, the researchers were able to detect traces of lidocaine, acetaminophen and other pharmaceuticals, chemicals from household cleaners, personal care and pet care products, as well as compounds from sunscreens and substances leaching from plastics in samples from the downstream recreation area. The downstream samples also contained human gut microbes.
However, water samples taken two days after Labor Day showed that the creek had returned to its original state, researchers said.
“The changes in the water may be short-lived, but that doesn’t mean they aren’t significant,” said lead author Noor Hamdan, a graduate student who conducted research in Prasse’s lab. “Flowing water carries the compounds further downstream, and that could impact plants and animals along the way.”
Co-authors include Johns Hopkins research associate Matthew Newmeyer and former Hopkins graduate student Veronica Wallace, as well as professors James Ranville and John Spear and graduate student Carmen Villaruel, all of the Colorado School of Mines.
This work was made possible by National Science Foundation CBET grant 2217526.
