The caffeine levels in Seattle's Puget Sound are so high that researchers recently had to scrap its efforts to use the substance as a marker to track the flow of wastewater, according to a report from the Seattle Post-Intelligencer.
Researchers saw caffeine as a promising marker because it does not happen naturally in the environment, is ingested only by humans and remains virtually unchanged as it passes through the body.
But the substance is everywhere in the Sound, because of drivers, and coffee cart operators who dump leftover coffee into storm drains.
From eight different monitoring stations in the sound, caffeine was found in more than 160 of 216 samples and at depths of up to 640 feet.
The researchers have abandoned their efforts to use caffeine to study the sound and Lake Washington. The county will likely use dye tests again.
The researchers said little is known about the effects of caffeine on wildlife, but the caffeine in Puget Sound is so diluted it probably has a minimal effect.
