Inter-laboratory validation of bioaccessibility testing for metals

•Intra- and inter-laboratory variability of bioelution tests were evaluated.•5 laboratories tested 6 metal-containing materials in 4 synthetic fluids.•Absolute bioaccessibility results in some fluids fluctuated between laboratories.•Within-lab variability was satisfactory for oral, inhalation, and dermal fluids.•Better-defined protocol needed to improve between-lab reproducibility.