Balsa Raft Crossing the Pacific Finds Low Contaminant Levels

During the Norwegian Tangaroa balsa raft expedition crossing the Pacific in 2006, surface water samples were collected by passive semipermeable membrane device (SPMD) sampling, active surface microlayer collection, and fish bile collection. The samples were analyzed for water contamination including a range of persistent organochlorine contaminants, pesticides, polycyclic aromatic hydrocarbons, as well as modern widespread chemicals such as brominated flame retardants, UV-filters, and perfluorinated compounds, using a network of expert laboratories and advanced instrumentation. Only trace to undetectable levels of all compounds were observed in both SPMDs and microlayer samples. The data from SPMDs were used to estimate surface water concentrations by back-calculation using sampling rates published in the literature. Conservative factors indicate that the levels in the surface waters are in the pg/L to subpg/L range for organochlorines, BFRs, and PFCs, indicating the central Pacific Ocean still represents a pristine environment for oceanic life.