Occurrence and concentration of caffeine in Oregon coastal waters

Background/Question/Methods

Caffeine, a biologically active drug, is recognized as a contaminant of freshwater and marine systems. To date, the majority of studies examining caffeine concentrations have focused on large bays and estuaries. However, coastal zones in less urbanized areas may also be affected by caffeine pollution. Here we present findings from a study examining Oregon’s coastal ocean to determine whether caffeine levels correlated with proximity to caffeine pollution sources. Caffeine was measured at 14 coastal locations, stratified between populated areas with sources of caffeine pollution and sparsely populated areas with no major caffeine pollution sources. Caffeine concentrations were also measured in the major water body discharging near sampling locations.

Results/Conclusions

Caffeine was detected in seawater at concentrations ranging from below the reporting limit to 44.7 ng/L. The occurrence and concentrations of caffeine in Oregon’s coastal ocean did not correspond well with pollution threats from population density and point and non-point sources, but did correspond with a storm event occurrence. Caffeine concentrations in rivers and estuaries draining to the coast ranged from below the reporting limit to 152.2 ng/L. This study establishes the occurrence of caffeine in Oregon’s coastal waters and results suggest that onsite waste treatment facilities may be a major source of caffeine to the coastal ocean. The relative importance of different sources, how sources vary seasonally, and processes affecting transport of caffeine in the coastal ocean require further research.