Caffeine at the coast

Caffeine detected in the sea off the coast of Oregon originates from storm run-off and not wastewater treatment plants, say US researchers. Zoe Rodriguez del Rey and Elise F Granek from Portland State University and Steve Sylvester from Washington State University collected seawater from 14 locations down the Orgeon coast adjacent to high and low population areas as well as from river water running into the sea.

Writing in Marine Pollution Bulletin, they described how they used GC/MS to measure the caffeine contents and came up with unexpected results. The highest caffeine levels were not alongside the most populated areas on land, suggesting that the wastewater treatment plants are managing to remove caffeine from the system. Instead, the highest concentrations corresponded to strong wet weather events, reaching the sea via storm run-off though strom drains. These drain systems bypass water treatment plants so any pollutants are directed to the rivers and out to sea.

Caffeine was not found at all test sites, which differs from reports at other locations around the world, but the researchers recognised that this might change at other times of year with different weather patterns and river flow conditions. Although the maximum level is only 44.7 ng/L, caffeine has been shown to accumulate in some marine species like mussels, and its effects on marine life are unclear.