Grand Canyon’s Springs Contain Traces of Drugs, PFAS

Water moving through one of America’s most celebrated natural wonders is carrying unexpected contaminants, according to a new federal study. Research by the U.S. Geological Survey and the National Park Service found traces of pharmaceuticals and “forever chemicals” in several springs along the Grand Canyon’s South Rim.

The study detected contaminants at sites including Bright Angel Wash, Monument Spring, and Upper Horn Bedrock Spring. Monument Spring, which drains into the Colorado River, contained low concentrations of multiple medications—such as an antibiotic, an antifungal drug, an antidepressant, and a diabetes treatment. Researchers believe the source is treated wastewater from the South Rim Wastewater Treatment Plant that is seeping back into the canyon’s groundwater.

Scientists also found several PFAS compounds, a group of long-lasting chemicals commonly used in products like nonstick cookware and waterproof clothing. PFAS have been linked to health risks including cancer and reproductive problems. While none of the detected pharmaceutical levels exceeded existing drinking-water standards, most of the substances identified do not have federal safety limits, making it difficult to determine acceptable exposure levels. The water samples were collected in spring 2021.

Environmental groups say the greatest concern is long-term exposure, particularly for wildlife that depends on these isolated desert springs. Amphibians such as frogs and salamanders may be especially at risk, as PFAS and some medications can disrupt hormones and reproduction, according to Mike Fiebig of the nonprofit American Rivers. Backcountry hikers who collect drinking water from the springs could also be exposed, though at low levels, since standard wastewater treatment systems are designed to remove pathogens—not complex chemical compounds.

Addressing the contamination could be challenging and expensive. Advanced water treatment technologies are available but costly, and the National Park Service is already dealing with tight budgets. Fiebig says treated wastewater may be traveling through the Bright Angel Fault and reemerging at the springs. Rerouting that flow could help, but it may simply move the problem to another area.

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