Coloradans taking to the water over Labor Day weekend might be bringing more than just inner tubes and floats with them, according to new research from the Colorado School of Mines and Johns Hopkins University.
Researchers took a closer look at the water in Clear Creek as it flows through a popular tubing area in Golden over Labor Day weekend in 2022 to get an idea of recreational impacts to streams and rivers. The small pilot study found elevated levels of lead, bacteria linked to the human gut, and signs of painkillers, cocaine and more in the water.
“You can almost think about it as a fingerprint of the activities that are going on,” said Carsten Prasse, an assistant professor in the Whiting School of Engineering at Johns Hopkins University.
Prasse and other researchers, including several at the Colorado School of Mines, combined their expertise in microbiomes, metals and chemical compounds to offer a unique and holistic look at recreation’s impacts on streams, published Thursday in ACS ES&T Water.
The researchers focused on a 1.5-mile stretch of Clear Creek popular for water activities like tubing and rafting. They gathered samples during and after Labor Day in 2022 from two locations: an upstream site, near a suspension bridge off Clear Creek Canyon Road west of Colorado 93, and further downstream at Ford Street in Golden.
The researchers found dozens of chemical compounds in the downstream location, which indicates they were introduced by the people recreating in Clear Creek, which begins near Loveland ski area. The creek also flows past the Coors Brewery in Golden and provides water for cleaning and other tasks in the plant, according to Axios.
What’s in Clear Creek?
They saw compounds associated with personal care and pet products, like flea medication, and lidocaine, a local anesthetic that can be found in over-the-counter topical creams. A large fraction of the compounds were related to plastics, like the plastic additive phthalate, Prasse said.
The researchers found signs of cocaine and painkillers, including acetaminophen, which is normally taken as a pill.
“What that probably means is that people are peeing in the water, which is not that surprising,” Prasse said. “We know from swimming pools that people do that all the time.”
They wanted to see if they could track mineral sunscreens, which includes metals, like zinc, but found that any metals from sunscreen were indistinguishable from the metals already in the water.
Not so with chemical-based sunscreens.
Common chemical compounds avobenzone and oxybenzone were found in Clear Creek, although the researchers did not tally the exact concentrations. These chemicals have been shown to harm corals in the ocean and algae in rivers, and they are banned in some places, like Hawaii, he said.
“Chemical-based sunscreen filters are probably, in my opinion, the more concerning compounds because we know these UV filters can be problematic for aquatic species,” Prasse said.
The researchers also found that the microbiome in the water shifted significantly during the high-use days. A lot of the bacteria that were introduced are associated with the human gut biome, which could be associated with poop particles coming off people or animals, Prasse said.
They did see more lead in the water, likely a legacy of mining in Colorado, he said. Clear Creek was the location of some of the most intense early mining activity during the Colorado Gold Rush, and upstream mining activity likely deposited heavy metals on the stream bottom.
The lead was likely suspended in the water in sediment kicked up by people, Prasse said.
By their final sampling day, just after the busy weekend, all of the stream conditions were back to normal as compounds and suspended sediment moved downstream, Prasse said.
“Are there also potential implications for the ecosystem that’s located downstream?” he said. “That’s something we weren’t able to address.”
Rivers under growing demand
The city of Golden is actively doing research on Clear Creek with help from the School of Mines. City staff is gathering data on tubing and pedestrian traffic and plans to share a report Oct. 8 at a city council study session, spokesperson Meredith Ritchie said.
“We are continuing to refine our processes to ensure the most accurate data is available, including cross-referencing with weather, camera data and special event populations,” Ritchie said in a written statement.
Statewide water quality data has shown that animal waste, too much lawn fertilizer, trash, toxic algae and storms washing pollutants off roads and into streams lead to pollution in waterways, according to the Colorado Department of Public Health and Environment.
River recreation has benefits for quality of life in Colorado and the state’s economy. Water sports directly contributed $1.1 billion to Colorado’s gross domestic product according to a 2020 report from Business for Water Stewardship, part of the environmental nonprofit Bonneville Environmental Foundation. Direct retail spending along waterways in Colorado generates an estimated $9.9 billion in economic output.
Colorado’s rivers are likely to see even more use in the future. The state’s population could reach 6 million by 2050, nearly double the 2008 population, according to a Conservation Colorado river assessment in 2020.
Clear Creek is a tributary of the South Platte River, which received a “D” rating for water quality in the assessment because of impacts linked to wildfires, legacy mines and warmer temperatures.
Tips for river recreation
For Prasse and the research team, the pilot study sets the stage for future research, which could focus on a longer period of time or calculate the concentrations of compounds in the water.
“Without concentrations, you can’t really say anything about any risks that might be there. We don’t know if there’s a risk,” Prasse said. “And there’s a lot of benefits of recreational activities. Like a lot of things, there’s pros and cons.”
Based on the 2022 Labor Day study, he said, there is no reason for concern for people swimming in Clear Creek or for the environment.
He encouraged people to use mineral sunscreens rather than chemical-based sunscreens, which have UV filters that are potentially problematic for humans and the environment.
The goal is to encourage recreators to think mindfully about what they’re taking on the water, whether it is skin products that can wash off you, food, drinks or anything else, Prasse said.
“The goal of this is definitely not to say, ‘Please don’t go tubing.’ That would be the wrong message,” he said. “There is more research that needs to be conducted to look into other potential negative implications of this.”