A Tiered Occupational Risk Assessment for Ceramic LDM: On-Site Exposure, Particle Morphology and Toxicity of Kaolin and Zeolite Feedstocks

A tiered approach is presented for evaluating occupational risks during liquid deposition modelling (LDM) using ceramic materials for manufacturing complex geometries in construction. The ceramic paste is comprised of kaolin/zeolite powders mixed with deionised water at a specific ratio. The tiered occupational risk analysis covered (i) the material evaluation and information gathering, (ii) on-site exposure measurements to ultrafine and micro-size particles, and (iii) morphological and toxicological analyses of raw and collected air samples. Results indicated an increase in PM4 (particle diameter < 4 μm) concentrations during powder preparation, reaching up to 1 mg/m3 during powder preparation, although below the corresponding substance-specific and general dust occupational exposure limit and with no increased exposure to ultrafine particles, as supported by morphological analysis. In toxicity assessment, reactive oxygen species production (ROS) reached approximately 300% for 50 μg/mL raw kaolin powder, while inducing high upregulation of TNF-α and IL-6 mRNA expression genes, indicating activation of pro-inflammatory pathways. Airborne samples resulted in cell viability reduction by ~50% at 40 μg/mL, showing significance (p-value < 0.001). Translating these findings to human risk remains difficult, yet the findings highlight an urgent requirement for continuous exposure surveillance, tailored toxicity evaluations, and robust protective strategies throughout ceramic manufacturing.