Validation of exposure models for generating estimate exposure to ultrafine particles among canadian welding apprentices

An exposure study in Quebec showed that apprentices in welding profession have a high level of exposure to ultrafine particles (UFP) during the whole training period. This is of increasing importance as evidence suggests that UFP may contribute to adverse respiratory and cardiovascular outcomes. Therefore, we aimed to evaluate how well existing empirical models for welding fumes estimate exposure to UFP among welding apprentices. We used an existing exposure database of 136 UFP measurements from two welding vocational schools in Quebec. We used three exposure models for inhalable dusts and fumes, respirable dusts and fumes, and total particulate matter to estimate UFP exposure among apprentice welders from Quebec. Pearson correlation coefficients were calculated between the estimated exposure to welding fumes based on the three models and measured UFP concentrations. We found low correlation coefficients between the measured UFP concentrations and the estimated welding fumes concentrations from the three exposure models that ranged from 0.11 to 0.22. Correlations coefficients between the estimates of the three models were markedly higher and ranged from 0.41 to 0.74. These findings suggest that current empirical models for exposure to welding fumes are insufficient for predicting exposure to UFP among welding apprentices. More UFP measurements are needed to derive UFP-specific empirical models. These models will be crucial for controlling exposure and to assess association of exposure to UFP and respiratory health effects.