Data are contaminants in tissue of caged mussels put in the river for 3 weeks at about 25 stations located on the Canadian and US side of the river. The main objective of the study is to identify contaminant sources, or source areas requiring more detailed follow-up investigations, based on the level of contaminants in the mussels. Compounds monitored include: * organochlorinated pesticides * Polychlorinated biphenyls * dioxins/furan * chlorinated benzenes * Polycyclic aromatic hydrocarbons * industrial organic compounds