Summer swimming and tubing alters water chemistry, researchers say

Tubing River
Scientists report preliminary results that show how recreation can alter the chemical and microbial fingerprint of streams, but the environmental and health ramifications are not yet known. Photo Credit: blueiz60,

Researchers say they used software and high-level instrumental analysis to determine whether summer swimming and tubing can alter the chemical and microbial fingerprint of Clear Creek in Colorado when compounds wash off people’s skin in sweat or urine.

The study compares the creek’s use on a busy Labor Day weekend in 2022, when as many as 500 people per hour use the stream for tubing and swimming, to a quieter weekday afterward, as well as an undisturbed location upstream.

“We found a lot of human metabolites, a lot of pharmaceuticals, some illicit drugs and some sunscreens — really a whole slew of compounds that humans are associated with,” explained Noor Hamdan, a graduate student who worked with the project’s lab samples and presented the findings at the fall meeting of the American Chemical Society (ACS). “Those compounds presumably washed off people’s skin or were released in sweat or urine, among other possible sources,” added Hamdan.

Preliminary results from lab tests indicated the presence of cocaine, the topical anesthetic lidocaine, antihistamines, seizure and bipolar disorder medications, as well as polyethylene glycol (used in medications and other applications), phthalates (plasticizers). Organic sunscreen ingredients such as avobenzone and oxybenzone, as well as UV filters, were also detected. 

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One of the first studies of its kind, it evolved from stream quality discussions between Carsten Prasse, an assistant professor of environmental health and engineering at The John Hopkins Whiting School of Engineering, and James Ranville, a department of chemistry professor at the Colorado School of Mines.  

Additionally, the lab results indicated that human recreation stirred up sediments in the creek and raised the water’s concentration of metals, such as copper, lead, zinc, aluminum and iron. Sediments could clog the gills of fish, making it harder for them to absorb oxygen from the water. Dissolved metals in the water could affect reproduction, species diversity and the health of aquatic species, the researchers noted.

The researchers used inductively coupled plasma-mass spectrometry and liquid chromatography-high resolution mass spectrometry. They found that human recreational activities such as swimming and tubing altered the creek’s microbial profile, increasing the abundance of microorganisms commonly associated with human waste. 

One important element, the researchers noted, is the lack of data available on long-term toxicity or persistence in the water bodies, as well as the exposure risks for a lot of the detected compounds. The team does plan to sample Clear Creek again later this year.

The researchers suggested that even peeing in local water bodies can have an impact on their natural chemistry.

“When you urinate into a toilet, the water goes to a wastewater treatment plant before it is discharged into a river,” said Prasse in an announcement. “But if you urinate into a river, all those chemicals go directly into the water. We know that things like pharmaceuticals can impact aquatic species, such as fish, even at very low concentrations.”

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