Caffeine and other tracers used to target wastewater pollution


Your daily coffee habit may someday help identify sources of bacterial pollution in Puget Sound. Researchers at the Puget Sound Institute are developing a new tool for targeting leaky septic tanks that may have broader implications for studies of emerging contaminants.

PSI researchers in collaboration with the Kitsap County Public Health District are studying ways to use wastewater tracers such as caffeine to identify leaky septic tanks and other sources of human-caused bacterial contamination. The study, supported by a $45,000 grant from The Russell Family Foundation looks at more than two-dozen potential compounds ranging from paraxanthine (a metabolite of caffeine) to ibuprofen, and spices like vanilla, artificial sweeteners and even sunscreen.

Polluted stream flows onto beach
Scientists are using emerging contaminants to target wastewater pollution. Photo: Andy James

Regulators say that bacterial pollution is one of the most significant water quality concerns in Puget Sound. Bacteria associated with human waste like E. coli and fecal coliform contribute to the closures of almost 20% of the region’s commercial shellfish beds and approximately 7,000 acres— a whopping 25%— of Puget Sound’s swimming beaches.

While there are already effective tests for measuring bacterial contamination, these tests don’t tell environmental managers the bacteria’s source. That prospect is rarely as simple as finding a leaky pipe oozing into a creek. “It can take some detective work,” says PSI researcher Andy James, one of the scientists leading the new study.

The challenge, James points out, is that humans aren’t the only creatures using Puget Sound. All those ducks and geese and sea lions, or the dogs and the nearby dairy farms? They can pollute the waters too. Both types of pollution—human and nonhuman—are considered unhealthy, but may require different regulatory approaches.

In response, the researchers have identified compounds used only by humans that occur in wastewater along with the bacteria. Finding caffeine—or any of the other tracer compounds — linked with bacterial contaminants suggests a human source, allowing environmental managers to target their efforts. Digging up septic tanks, for example, can be expensive. Ruling out a human source with a simple water test could save time and money.

Currently, there are other methods of identifying human-associated bacteria through DNA sequencing, but using wastewater tracers “is potentially quicker and less expensive than other methods,” says James. “This isn’t going to solve all the problems, but it might give resource managers more information to solve the problem.”

This month, the group began sampling at locations with known and unknown sources of contaminants around Kitsap County. The study extends through the year and looks at a wide variety of potential tracers, including caffeine, ibuprofen and sucralose, an artificial sweetener used in Splenda and found in Diet Coke and other low-cal food products. Other compounds include vanillin and ethyl-vanillin, and ensulizole, a U.V. blocker found in sunscreen.

Fundamental to this research is the link between bacteria and emerging contaminants. These compounds are not just associated with leaky septic tanks. They also pass through water treatment plants and go directly into Puget Sound. Scientists want to know if these chemicals— not just the associated bacteria— are damaging to the environment. Some tracer compounds in the study such as ibuprofen are already thought to be toxicologically significant, with environmental concentrations high enough to cause potential (but unknown) effects in organisms. Researchers hope that their work can contribute to the body of knowledge related to emergent contaminants in Puget Sound.

“Right now, there isn’t much data on emerging contaminants, and at a minimum, this will add to that data set,” says James.

Groups such as the Puget Sound Ecosystem Monitoring Program (PSEMP) are beginning to study the significance of the many human-associated chemical compounds flowing into Puget Sound, from pharmaceuticals to chemicals in processed food. James serves on the PSEMP toxics workgroup, which hopes to identify emergent contaminants that might be especially harmful to Puget Sound wildlife.