Evaluation of the bio-accessible non-process element concentrations in slaker grits by synthetic sweat and gastric fluids extraction

Aim: The non-process elements (NPEs) or more correctly inorganic process contaminants are compounds that are not necessary for the chemistry of kraft pulping, e.g. heavy metals. The aim of this study was to determine the extractability of NPEs in the slaker grits using artificial sweat and gastric fluids to assess the potential occupational risk from grits handling. Methods: The slaker grits investigated in this study were sampled in November 2013 from the outlet of the causticizing process at a pulp mill located in Finland. The bio-accessible concentrations of NPEs in the slaker grits were determined using their solubility (extractability) in synthetic sweat (pH = 6.4) and gastric (pH = 1.5) fluids. Results: The highest bio-accessible concentration of non-process elements (NPEs) in the synthetic sweat fluid was observed for Al (14.0 mg/kg; d.w.), and in the synthetic gastric fluid for Al (4920 mg/kg; d.w.) and Ba (163 mg/kg; d.w.). If we disregard the NPEs whose concentrations were lower than the detection limits, the synthetic gastric fluid was able to release between 42.6% (Pb) and 81.8% (Ni) of the total element concentrations of NPEs in the slaker grits. Conclusion: We conclude that due to the very high bio-accessible concentration of certain NPEs in the synthetic gastric fluid, it is necessary to prevent the ingestion and penetration of slaker grits particles across the human gastrointestinal tract.