Polycyclic aromatic hydrocarbons (PAHs) in traditionally harvested bivalves in northern British Columbia, Canada

Butter clams, blue mussels, and Nuttall's cockle are important traditional food of the Gitga'at First Nation in Canada. Samples were collected and analyzed for polycyclic aromatic hydrocarbon (PAH) from the Gitga'at harvest sites from 2006 to 2015 to: 1) establish baseline conditions; 2) determine the likely source; 3) understand species specific response to spills; and 4) evaluate health risk associated with consumption. Baseline lipid normalized-total PAH in mussels was 2.36 (+/- 2.86, 95%CI) mu g/g in mussels, 3.26(+/- 4.14) mu g/g in clams and 3.98 (+/- 4.98) mu g/g in cockles. PAHs varied according to proximity to point sources and became less petrogenic through time. Concentrations of PAHs were elevated in all three species following diesel spills but returned to baseline levels within 5 months. However, Gitga'at harvesters avoided bivalves from spill-affected habitats for several years because of their detection of reduced quality and palatability, highlighting the importance of incorporating local knowledge into future monitoring programs.