the concentrations of cu, zn, pb, and cd were determined in the mussel mytella falcata from the bacanga river estuary, in order to evaluate the potential role of domestic effluents released "in natura" on the quality of the estuarine environment with consequences to shellfish resources. cu concentrations ranged from 5.2 mg.g-1 to 13.1 mg.g-1, while zn concentrations ranged from 49.1 mg.g-1 to 76.3 mg.g-1. pb and cd showed concentrations lower than 2 mg.g-1. the results showed low concentrations of cu, pb and cd in the filter-feeding mytella falcata in the study area in comparison with the maximum values stablished to foods by the brazilian government (decree law no 55,871). finally, zn presented slightly higher values than the maximum ones stablished by the brazilian government.