Exposure to hexavalent chromium in welders: Results of the WELDOX II field study

Exposure to hexavalent chromium (Cr(VI)) has been primarily studied in chromate production. Here, we measured personal exposure to respirable Cr(VI) together with airborne and urinary Cr and Ni in welders to explore levels and associations between various measures of exposure.

Shift concentrations of Cr(VI), Cr, and Ni were measured in respirable welding fumes in 50 men who used either gas metal arc welding (GMAW) (n = 24) or tungsten inert gas welding (TIG) (n = 19) as their major technique. Cr and Ni were determined in pre- and post-shift urine samples. Concentrations below the limit of quantification (LOQ) were multiply imputed. Spearman correlation coefficients (rs) were calculated with 95% confidence intervals (CIs) to explore associations between the exposure variables, and regression models were applied to estimate the effect of the parent metal on the urinary concentration.

Regarding the respirable Cr(VI), 62% of the measurements were below the LOQ, the 75th percentile was 0.50 µg m-3, and 8 out of 50 (16%) welders exceeded 1 µg m-3. The highest shift concentration that occurred as a result of shielded metal arc welding (SMAW) was 180 µg m-3. The Cr(VI) content in total Cr ranged from 4 to 82% (median 20%), although the concentration correlated with total Cr (rs 0.55, 95% CI 0.46; 0.64). The correlation between Cr(VI) and Ni was weaker (rs 0.42, 95% CI 0.34; 0.51) than that between total Cr and Ni in welding fumes (rs 0.83, 95% CI 0.74; 0.92). Both Cr(VI) and total Cr influenced the urinary Cr concentrations in post-shift samples (P = 0.0008 and P ≤ 0.0001, respectively). The airborne shift exposure was a weaker determinant than the Cr content in pre-shift urine samples, which strongly correlated with post-shift urinary Cr (rs 0.78, 95% CI 0.69; 0.87).

The Cr(VI) content in total Cr varied considerably in welding fumes. The majority of welders using GMAW or TIG presented with shift concentrations of respirable Cr(VI) below 1 µg m-3. However, very high Cr(VI) concentrations may occur, for example in SMAW. The urinary concentration of total Cr, cannot be used to precisely determine the shift concentration of respirable Cr(VI) in welders.