Occurrence and concentration of caffeine in Oregon coastal waters

Caffeine, a biologically active drug, is recognized as a contaminant of freshwater and marine systems. We quantified caffeine concentrations in Oregon’s coastal ocean to determine whether levels correlated with proximity to caffeine pollution sources. Caffeine was analyzed 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 measured in major water bodies discharging near sampling locations. Caffeine in seawater ranged from below the reporting limit (8.5 ng/L) to 44.7 ng/L. Caffeine occurrence and concentrations in seawater did not correspond with pollution threats from population density and point and non-point sources, but did correspond with 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, yet relative importance of sources, seasonal variability, and processes affecting caffeine transport into the coastal ocean require further research.