Boston Pee Party.

Millions of coffee drinkers may be providing the ultimate environmental wake-up call. So much caffeine flows into and out of people daily that it could offer the best test yet for water pollution, says a scientist in Boston, Massachusetts, who has measured the caffeine content of the city's harbor.

Sewage spills are now detected by checking for strains of fecal Escherichia coil bacteria, which themselves are often not harmful but suggest the possible presence of potentially dangerous pathogens such as Salmonella and the hepatitis B virus. But that test is slow to yield results, and it doesn't indicate whether the bacteria came from animals or humans, which could provide a clue as to whether the waste is harmful.

So the search is on for a quick and easy marker for human sewage. Robert Chen, an oceanographer in the Environmental, Coastal, and Ocean Science Department of the University of Massachusetts Boston, thinks the answer may be caffeine. It is perhaps the world's most popular psychoactive drug--about 90% of Americans consume caffeine every day in the form of coffee, tea, soft drinks, and other products. Chen says the body absorbs and metabolizes 94-99% of the caffeine consumed. While nearly all caffeine is transformed to a variety of metabolites, as much as 20% passes intact through the body and sewage filtration systems, and may reach coastal waters. "That's a small amount of the original caffeine ingested, but it makes for a huge amount of a trace molecule," says Chen.

Chen and graduate student Ray Siegener established the baseline caffeine component of Boston Harbor by repeatedly measuring six sites in the water using gas chromatography-mass spectrometry. This baseline caffeine concentration, which comes from treated wastewater that is pumped miles out into Massachusetts Bay, reflects the small percentage of caffeine not eliminated by sewage treatment. Anything above that level could indicate the occurrence of a sewage spill. By taking readings at many points within a body of water and finding where the readings are highest, it may be possible to trace a spill back to its source.

Chen and his colleagues are now computing the relationship of caffeine to more harmful chemicals. For example, says Chen, for every 10 parts of caffeine found in treated water, there may be 1 part of a different substance that is, say, an endocrine disruptor. Abnormal amounts of caffeine might then indicate that higher-than-acceptable levels of the endocrine disruptor will be found in the water. "Everyone is looking for that magic single indicator of sewage," he says.

Says Christian Daughton, chief of the Environmental Chemistry Branch of the Environmental Protection Agency (EPA) National Exposure Research Laboratory, "For the purposes of tracing sewage, in some locales there may be too much caffeine introduced to open water, both from human excretion to domestic sewage and by disposal of leftover coffee to sewage systems and via storm drains [by dumping coffee out onto the ground]." On the other hand, he says, "Caffeine may exist for just the right amount of time to serve as a signal of pollution. It is a delicate balancing act because the tracer has to survive sufficiently long to have a chance to see it, but not so long that you always see it."

But caffeine may prove inadequate as a sole marker of human sewage, say several environmental chemists. According to a 3 July 2000 Associated Press article, studies in Puget Sound discovered caffeine everywhere in otherwise relatively clean waters, rendering the marker invalid. Susan Glassmeyer, a research chemist in the National Exposure Research Laboratory, says what is needed is a "mass fingerprint" of 10-15 compounds, a mix of pollutants including drugs, bleaching agents, surfactants, compounds produced by the human body such as coprostanol, and yes, caffeine. She and her team are developing such a test using liquid chromatography-mass spectrometry.