Evaluation of Three Traditional Curing Methods Applied in Mexican Lead-Glazed Ceramics: Detection, Concentration, and Leaching of Lead to Food

In Mexico, the main source of lead (Pb) exposure is the use of lead-glazed ceramic (LGC). Curing is a traditional technique employed to seal the pores of ceramic, enhancing resistance to high temperatures and moisture absorption. One common belief, sometimes promoted by governmental sources, is that this practice can also remove Pb from LGC. In this study, we evaluated the effect of three traditional curing methods (oil/heat, boiling water/lard, and garlic/boiling vinegar) on Pb detection, concentration and leaching in three LGC pieces. Before and after curing, detection (LumetallixTM and sodium rhodizonate) and concentration (XRF) were measured; meanwhile, leaching after curing was evaluated by ICP-MS in a simulated solution. All pieces were positive for Pb detection. Mean Pb concentration before curing was 164,400 ppm and increased on average to 266,700 ppm after curing, exceeding the limits established for ceramics (100 ppm). The highest level of Pb leaching was in the piece cured with oil/heat (378.18 ppm) followed by garlic/boiling vinegar (2.6 ppm), both exceeding the Mexican Normativity for leaching (0.5 ppm). We find that traditional curing should not be considered as a practice to remove Pb. Even worse, it may increase its availability and leach into food, increasing the health risk to consumers.