Abstract
Translating particle dose from in vitro systems to relevant human exposure remains a major challenge for the use of in vitro studies in assessing occupational hazard and risk of particle exposure. This study aimed to model the lung deposition and retention of welding fume particles following occupational scenarios and subsequently compare the lung doses to those used in vitro. We reviewed published welding fume concentrations and size distributions to identify input values simulating real-life exposure scenarios in the multiple path particle dosimetry (MPPD) model. The majority of the particles were reported to be below 0.1 μm and mass concentrations ranged between 0.05 and 45 mg/m3. Following 6-h exposure to 5 mg/m3 with a count median diameter of 50 nm, the tracheobronchial lung dose (0.89 µg/cm2) was found to exceed the in vitro cytotoxic cell dose (0.125 µg/cm2) previously assessed by us in human bronchial epithelial cells (HBEC-3kt). However, the tracheobronchial retention decreased rapidly when no exposure occurred, in contrast to the alveolar retention which builds-up over time and exceeded the in vitro cytotoxic cell dose after 1.5 working week. After 1 year, the tracheobronchial and alveolar retention was estimated to be 1.15 and 2.85 µg/cm2, respectively. Exposure to low-end aerosol concentrations resulted in alveolar retention comparable to cytotoxic in vitro dose in HBEC-3kt after 15–20 years of welding. This study demonstrates the potential of combining real-life exposure data with particle deposition modelling to improve the understanding of in vitro concentrations in the context of human occupational exposure.
Highlights
Welding fumes are created as a by-product of the welding process and contain toxic metals including chromium, nickel and manganese that are of concern for occupational health
The results reveal the concern of primarily tracheobronchial retention for short-term exposure to welding fumes, whereas alveolar retention is built up over time and of more concern for chronic exposure
Our results further suggest that lung doses retained following real-life occupational exposure scenarios of welders can be compared to cell doses found to elicit a toxic effect in vitro
Summary
Welding fumes are created as a by-product of the welding process and contain toxic metals including chromium, nickel and manganese that are of concern for occupational health. 10 million people are estimated to somehow be exposed to welding fumes in their occupational setting (IARC 2017), where the metal-containing fumes have been linked to several health outcomes including bronchitis, respiratory irritation, and inflammation (Antonini 2003; Zeidler-Erdely et al 2012; Riccelli et al 2020). Extrapolating human health risk from chemical exposure based on in vitro data is a challenging task. One important aspect lies in the in vitro dose selection, where scientific justification and consideration for real world exposure is crucial to provide useful data for toxicological hazard and risk assessment (Oberdörster and Kuhlbusch 2018; Romeo et al 2020)
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