Modelled lung deposition and retention of welding fume particles in occupational scenarios: a comparison to doses used in vitro

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.

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“…Tools have been developed to predict lung deposition, using models such as the International Commission on Radiological Protection (ICRP) and multiple-path particle dosimetry (MPPD), because con rming lung deposition by inhalation in every experiment is challenging (Löndahl et al 2014). The Environmental Protection Agency (EPA) recently released a user guide for the MPPD model [EPA/600/R-20/406], and multiple studies have utilized this model to predict the respiratory deposition of chemicals and incorporate it into risk assessments (Borisova et al 2023, McCarrick et al 2022a). The MPPD model has been used in numerous studies to predict the amount chemicals deposited in the lungs during inhalation.…”