In vitro toxicity of welding fumes and their constituents

Welding fumes from a wide variety of processes and applications were assayed for toxicity with BHK21 cell line and SHE primary cells in culture. The most toxic fumes are those from the manual metal arc welding of stainless steel (MMA/SS) (LD50 = 7-14 microgram/ml), although all other welding fumes tested are toxic, with potencies lower by a factor of 10-200. The activity of MMA/SS is presumably due to the presence of high concentrations of Cr(VI) in the soluble fraction: For all other fumes the lowered activity (LD50 = 80-800 microgram/ml) is limited mostly to the insoluble fraction, and in part can be related to the presence of MnO2 and Fe3O4 which are toxic at such levels in these cell culture assays. Slight discrepancies between survival tests for the two cell lines, and between survival and lactate dehydrogenate release for BHK, indicate a differential response to certain constituents of these complex materials. These results suggest the need for a battery of different types of assays for use in an eventual ranking of exposures for the purpose of relative risk assessment.