Interest and limitations of a lead, cadmium, and arsenic leachability study to estimate the toxicity of ancient ceramics (Ecuador & Ghana)

Abstract

From 34 ceramic sherds excavated from 6 archaeological sites in Ecuador and Ghana, we tried to determine whether these ceramics previously intended to be in contact with food were safe regarding lead, cadmium and arsenic migration. We anticipated ceramics leachability results may be noticeably different with respect to country of origin and presence/absence of slip. Eighteen Equatorian and 16 Ghanaian pieces were immersed into 4% acetic acid. Leached Pb, Cd and As were measured using Inductively-Coupled Mass Spectrometry (ICP-MS) on a NexION® 5000 triple-quadrupole ICP. No sample exceeded the concentration limits for lead and cadmium. 2 samples exceeded the arsenic limit. Statistically significant differences for distributions of lead and cadmium concentrations, and for lead leachability were highlighted between Ecuadorian and Ghanaian samples. Differences in cadmium concentrations and lead leachability were found between slipped and bare samples. Though, our study proved to be limited as regards long-term passage through the ground, cracks, experimental vs. real life conditions of use and validity of regulatory limitations. With the exception of two sherds exceeding the arsenic toxicity limit, our study enabled us to conclude that the tested ceramics did not present worrying levels of toxicity, within the limits of a retrospective analysis.