Construction and validation of a matrix for the estimation of exposures in the welding trades: a three-part series

• Author / Creator

  Galarneau, Jean-Michel, François

• Introduction:
  This three-part series of papers aimed to construct and validate an exposure matrix that would be used to estimate personal airborne exposures to total dust, manganese, nickel, chromium and aluminum for welders in the What-me cohort. The Workers’ Health in Apprenticeship Trades: metal and electrical (What-me) study established a cohort of both women and men welders for the purposes of investigating pregnancy and other birth outcomes along with general health issues related to welding. To achieve this, data were extracted and assembled from the literature and later analyzed to produce exposure models. Final models derived in this first step were then validated through the use of external data gathered under controlled conditions. Finally, exposure estimates were made for all welders in the cohort and using the exposure matrix developed an investigation of the relation between exposures and urinary metals analysis was undertaken.
  Methods:
  A systematic literature search was first conducted to identify and extract all relevant data from published journal articles appearing in selected databases. Summary data were extracted that represented airborne personal exposures to total, inhalable and respirable dusts along with metal concentrations for manganese, nickel, chromium and aluminum. Mathematical exposure models were derived from these data and a validation of the models undertaken in the second part of this study. To do this, the most common welding combinations of welding process, base metal and consumable (welding scenarios) for welders taking part in the What-me study were identified through detailed welding questionnaires. These were replicated under controlled conditions with a welder equipped with a personal air sampling pump to gather samples. A gravimetric analysis was later performed to determine total dust exposures followed by a metals analysis using ICP-MS. Predictions were made for these scenarios using the exposure models derived in the first step of this study and correlated against the results from the welding scenario replication. Lastly, exposures to manganese, nickel, chromium and aluminum were estimated using the welding exposure matrix described above and analysed against spot urine samples taken from welders between 2011 and 2016. The estimated exposures were correlated against urinary metal concentrations followed by linear regressions of urinary metal concentrations including exposure estimates as a predictor of urinary metals.
  Results:
  The systematic review process yielded 92 published articles from which 737 summary statistics were extracted representing 4620 personal samples of total dust, 4762 of manganese, 4679 of nickel, 3972 of chromium and 676 of aluminum. The highest total dust exposures were for flux-core arc welding (FCAW) while the highest manganese producing base metal was for mild steel. For nickel, the highest emissions were from high alloyed steel using gas metal arc welding (GMAW) while chromium emissions were most abundant in manual metal arc welding (MMAW) on stainless steel. Aluminum exposures were highest in FCAW welding and on aluminum as a base metal. The scenario replication part of this study identified 21 scenarios covering more than 90% of the scenarios in the What-me study. Sixty-one welding sessions took place with a minimum of two replicates per scenario. Spearman rank correlations between predicted exposures and mean measured exposures resulting from the scenario replications yielded a rho of 0.93 (p<0.001) for total dust, 0.87 (p<0.001) for manganese, 0.54 (p<0.024) for nickel, 0.43 (p=0.055) for chromium and 0.29 (p=0.210) for aluminum. Spot urine samples were gathered from welders and linked to an exposure estimate resulting in 204 samples from women and 225 samples from men. Spearman rank correlations between urinary metal concentrations and estimated metal exposures yield a rho of 0.08 (p=0.181) for manganese, 0.081 (p=0.093) for nickel, 0.14 (p<0.005) for chromium and 0.13 (p<0.01) for aluminum. Linear regression showed chromium and aluminum as having strong positive log linear relations between estimated exposures and urinary metal concentrations while manganese and nickel showed weaker ones.
  Conclusion:
  This study produced the first validated welding exposure matrix composed of process, base metal and consumable. This matrix was able to accurately predict exposures observed under controlled conditions while also predicting urinary metal concentrations in an existing cohort providing additional validity to the matrix developed here. This matrix can be used by any researcher to estimate welding exposures in a multitude of occupational contexts.

• Subjects / Keywords

  • welding
  • exposures
  • matrix
  • metal exposures
  • airborne exposures

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-wss2-az80

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.