Previous assessments of a selection of face masks intended for the general population in Belgium found that silver (Ag)-based biocides were present in masks advertised for antimicrobial properties; whereas titanium dioxide (TiO) particles were detected in all the face masks in at least one layer corroborating its widespread use in the textile industry. The presence of Ag-based biocides and TiO particles in face masks raised questions on the possibility of release under normal wearing conditions, which could potentially cause a health risk to the consumers. Direct measurement of release of Ag and TiO particles during normal wearing is problematic by the lack of methodology to test release and to quantify inhaled particles. Therefore in this study, we investigated leaching experiments using artificial acid sweat as a method to evaluate the release of Ag-based biocides and TiO particles present in face masks. Leaching experiments were proposed as an alternative method to evaluate the quality of face masks, and as a higher tier method to assess face masks that are not safe-by-design. Results from leaching experiments showed that Ag was released in amounts varying from 0.03 up to 36 % of total Ag content, in four out of the eight face masks that claimed antimicrobial properties and that contained Ag. The leaching data of titanium (Ti) showed that despite TiO being detected in all face masks, only in one mask Ti was measured in detectable concentrations in artificial sweat (0.35 % of total Ti content). Comparison of leachable Ag and Ti with respective acceptable exposure limit values derived from inhalation exposure limits indicate that three face masks would need further risk assessment and could not be considered as intrinsically safe.
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