Copper alloys' metal migration and bioaccessibility in saliva and gastric fluid

The oral bioaccessibility of copper alloys and pure metals was assessed using in vitro methods with synthetic saliva and gastric fluid. The metal-specific migration rates from polished alloy surfaces are higher in gastric (pH 1.5) than in saliva fluid (pH 7.2). In both media, migrations are higher for lead than for other metals. The bioaccessible metal concentrations in massive copper alloys, after 2 h in gastric fluid, was only <0.01%-0.18%, consistent with the low surface reactivity of copper alloys (defined as 1 mm spheres). The average metal-specific migrations of cobalt, copper, nickel and lead from most of the tested copper alloys in gastric media are comparable to the ones from their pure metals. The data further show that the bioaccessibility of metals in massive copper alloys primarily depends on the bioelution medium, the exposed surface area and the composition of the alloy. The tested copper alloys show only limited evidence for influence of alloy surface microstructure. This is contrary to findings for other alloys such as stainless steel. Additional investigations on other copper alloys could allow to further refine these conclusions. These findings are useful for establishing the hazard and risk profile of copper alloys following oral exposure.