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The aim of this study was to determine factors influencing observed increased metal biomarkers of exposure levels in a group of 116 Quebec apprentice welders during a longitudinal follow-up of exposure. Analysis of 14 metals was carried out in hair, fingernail, and toenail samples taken from participants over the course of their welding curriculum at 6 different times. Personal and socio-demographic characteristics, lifestyle habits, and other potential confounding factors were documented by questionnaire. Multivariate linear mixed-effect models were used to assess main predictors of metal concentrations in each biological matrix including increasing time of exposure throughout the curriculum (defined as the repeated measure "time" variable"). Significant associations between repeated measure "time" variable and metal levels in hair, fingernails, and toenails were found for chromium, iron, manganese and nickel. Significant associations with "time" were also noted for arsenic levels in hair and fingernails, and for barium, cobalt and vanadium levels in fingernails and toenails. The repeated measure "time" variable, hence increasing time of exposure throughout the curriculum, was the predominant predictor of elevated biological metal levels. Reduced spaces and simultaneous activities such as oxyfuel-cutting and welding in the same welding room were suspected to contribute to higher metal levels. Age, ethnicity, and annual household income exerted an effect on metal levels and considered as confounders in the models. Variations observed in metal levels between hair and nails of apprentice welders also emphasized the relevance and importance of performing multi-matrix and multi-element biomonitoring to assess temporal variations in biological metal concentrations during welding curriculum. [ABSTRACT FROM AUTHOR]

Canada has recently invested in the large-scale exploitation of scandium oxide. However, there are no studies available to date to understand its toxicokinetics in the animal or human body, which is necessary to assess exposure and health risks. The aim of this research was to investigate the toxicokinetics of absorbed scandium oxide (Sc 2 O 3) using the rat as an experimental model. Male Sprague-Dawley rats were injected intravenously with 0.3 or 1 mg Sc 2 O 3 /kg body weight (bw). Blood and excreta (urine and feces) were collected sequentially during a 21-day period, and main organs (liver, spleen, lungs, kidneys, brain) were withdrawn at sacrifice on day 21. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for the measurement of Sc element in the different samples. The mean residence time (MRT IV) calculated from the blood profile was 19.7 ± 5.9 h and 43.4 ± 24.6 h at the lower and higher doses, respectively. Highest tissue levels of Sc were found in the lungs and liver; respective lung values of 10.6 ± 6.2% and 3.4 ± 2.3% of the Sc dose were observed at the time of sacrifice while liver levels represented 8.9 ± 6.4% and 4.6 ± 1.1%. Elimination of Sc from the body was not complete after 21 days. Cumulative fecal excretion over the 21-day collection period represented 12.3 ± 1.3% and 5.9 ± 1.0% of the lower and higher Sc doses, respectively, and showed a significant effect of the dose on the excretion; only a small fraction of the Sc dose was recovered in urine (0.025 ± 0.016% and 0.011 ± 0.004% in total, respectively). In addition to an effect of the dose on the toxicokinetics, results highlight the importance of the lung as a site of accumulation and retention of Sc 2 O 3 , which raises the question of the risks of effects related to respiratory exposure in workers. The results also question the relevance of urine as a matrix for biological exposure monitoring. A more in-depth inhalation toxicokinetic study would be necessary. • Intravenously injected scandium oxide accumulates in lungs and liver mainly. • Excretion occurs mainly in feces and little is found in urine. • The dose impacts the toxicokinetics of scandium oxide. • Higher scandium oxide dose resulted in lower cumulative excretion rates. • Lung retention raises the question of risks related to respiratory exposure. [ABSTRACT FROM AUTHOR]