Assessing and mitigating health risks of workers exposed to volatile organic compounds in contaminated soils during active pit excavation: Accounting for exposure variability and uncertainty

Health risks to workers involved in the active pit excavation of volatile organic compound (VOC)-contaminated soils have been overlooked, despite the prevalence of ex-situ remediation practices in China. This study developed a new VOC exposure in pit excavation (VEPE) model that comprehensively accounts for the release of gasphase VOCs in soil pores, surface volatilization of newly exposed agglomerates, and volatilization of newly exposed excavation pit bottom surfaces. Additionally, the model incorporates the concentration variation of soil contaminants, spatial heterogeneity of soil properties, and the variability and uncertainty of worker exposure using two-dimensional Monte Carlo simulation (2D MCS), highlighting the importance of controlling area of new exposure surfaces, soil saturation, and air exchange during the pit excavation to mitigate risks. The study evaluated worker-health-based risks during the excavation of a VOC-contaminated site in Beijing and revealed that the inhalation cancer risk for trichloroethylene (2.35 x 10(-6)) and its hazard quotient (143.92) exceed the acceptable levels (10(-6) and 1.0, respectively). The comparison of models demonstrated the theoretical advancements of the VEPE model over existing pit excavation models, while the field test comparison showed a significant improvement in the predication accuracy. This study addresses the under-researched area of worker safety in contaminated excavation sites. The findings have the potential to promote cleaner and more sustainable practices in ex-situ contaminated site remediation by providing valuable insights for implementing effective control measures to mitigate the emission of toxic VOCs, thereby reducing adverse social and environmental impacts.