Chemical in coffee becomes a marker for human waste

A person’s morning coffee or over-the-counter pain killers could provide key evidence in the hunt for sources of bacterial pollution, experts have learned.

In tracking down pollution, officials with Kitsap Public Health District in Kitsap, Wash., can normally locate one or more failing septic systems or a yard full of dog waste and ask people to fix the problems, said Shawn Ultican, a water-quality investigator with the district. But sometimes the search for a source hits a dead end, with no apparent human connection.

Ultican is engaged in an experiment, now in its second year, to determine if a simple test can demonstrate the presence of human waste, as opposed to what might be coming from wildlife — such as neighborhood raccoons and birds.

Since animals don’t drink coffee, Ultican and his associates presumed that finding caffeine in a polluted stream could be a telltale indicator that humans were causing the problem. They also tested more than 20 other chemicals with a human connection, including over-the-counter drugs, prescription drugs, food ingredients and household chemicals.

Last year, they searched for these compounds in numerous streams, seeps and stormwater pipes throughout the county, some sites with known sources of pollution and other sites taken from the health district’s mystery files.

Results from all the water sampling recently were compiled with the help of the University of Washington’s Center for Urban Waters in Tacoma, Wash. Some of the compounds were found essentially everywhere in varying concentrations, Ultican noted. Others were not detected at all, even when known human sources of pollution were present.

“But some of the compounds are quite promising,” he said.

The researchers discarded caffeine as an indicator of human waste, because someone could dump a cup of coffee on the ground, where it could get into stormwater. In that case, a positive test for caffeine would not point to a source of pollution. They settled instead on paraxanthine, which is a breakdown product of caffeine excreted in urine. That one turns out to be a good indicator of waste from coffee drinkers.

Likewise, the researchers discarded nicotine as an indicator of a human source, because the chemical can show up when cigarettes are tossed on the ground. It turns out that cotinine, a metabolite of nicotine, provides a good test for human waste.

Two pain killers — ibuprofen and acetaminophen — turn out to be good indicators, along with sulfamethoxazole, an antibiotic.

No single chemical can be used, Ultican said, because not everyone drinks coffee or smokes cigarettes or takes specific medications. But if all five chemicals are tested, the odds increase that at least one chemical will be present when the pollution comes from human sources, he said.

The exact methods of using this chemical test have not been worked out, Ultican said. As a backup of sorts, investigators are considering other chemical tests, such as looking for the artificial sweetener sucralose, the mood-stabilizing drug carbamazepine or the common herbicide mecaprop. While these chemicals are widespread in low concentrations, finding them at higher levels could be an indicator of pollution from people, he said.

The chemical test for these various compounds is not a substitute for normal detective work, which involves bacterial tests of surface waters, visual searches for potential problems, discussions with neighbors and dye-testing suspect septic systems.

“Having a good working knowledge of what is happening in the watershed is part of any investigation,” Ultican said. “If we can’t find obvious sources, we would turn to this tool.”

Study findings will be presented at the biennial Salish Sea Conference at the end of April and at a conference for environmental health professionals in May. The study will be published in a formal report and submitted for publication in a scientific journal.

Until now, the only reliable way to identify a human source of pollution was with expensive DNA testing.

More precise testing protocols using common chemicals will be developed, Ultican said, and he expects to use results for some of Kitsap’s polluted mystery sites. One is Lofall Creek in North Kitsap, where all known human sources have been tracked down and cleaned up, yet bacterial problems persist.

A final round of sampling was concluded last week, when investigators returned to sites that had known sources of human pollution. Now, those sites have been cleaned up, either when septic systems were repaired or when homes were abandoned — as with one house in Illahee. When the chemical analysis is complete, the researchers will have a before-and-after picture of pollution from those sites.

The yearlong research project, extended into a second year, was funded with a $42,000 grant from the Russell Family Foundation. Most of the money was spent for the chemical testing.

To make the testing more routine, one or more testing labs must be brought on board. Multiple counties could contract with the same labs to increase efficiencies and hold down costs, Ultican said.

The next phase of the investigation could involve one of the counties in northern Puget Sound where livestock pollution can be a problem, he said. As with humans, certain livestock feeds, medications and chemical treatments could become markers for the presence of livestock waste.

“This method will probably evolve over the next few years,” Ultican said. “It’s usable now, but there’s room for improvement.”

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