This study was performed to determine the in vitro degradation rate of tungsten coils and to evaluate the potential local toxicity of tungsten on human pulmonary arterial endothelial (EC) and smooth muscle cells (SMC) and human dermal fibroblasts (FB). Therefore, tungsten coils were immersed in Ringer's solution and loss of mass and increase in tungsten concentration in the electrolyte were assessed in relation to immersion time (maximum: 140 days). Primary cultures of EC, SMC and FB were grown on multiplates for 1-10 days with ascending concentrations (0.1-5000 microg/ml) of tungsten in the growth medium. Metabolic activity was assessed by the use of the WST-1 Test (Roche). The in vitro degradation rate of the tungsten coil was 29 microg/day. EC were most susceptible to tungsten with a LD50 of 50 microg/ml. In contrast, the LD50 for SMC was 100 and 1000 microg/ml for FB after 10 days of incubation. We conclude that, in vitro, degradation rate of tungsten coils is slow (29 microg/day). Very high (>50 microg/ml [normal serum value 0.0002 microg/ml]) tungsten concentrations are needed to result in local cytopathologic effects on human EC, SMC and FB. These results correspond to clinical observations demonstrating the absence of toxicity of degrading tungsten coils in adult and pediatric patients despite elevated serum tungsten levels.