Can the inhalation exposure of a specific worker in a cross-ventilated factory be evaluated by time- and spatial-averaged contaminant concentration?

Industry implies economic growth; however, outdoor and indoor air pollution generated by industrial activities represents a widespread problem for the environment and human beings. In terms of human health, indoor air quality assessment has become essential in a society where people spend most of their time in indoor dwellings, as in the case of industry workers. Because indoor air quality is strongly affected by the outdoor environment, especially under natural ventilation conditions (e.g., cross-ventilation), a comprehensive analysis that includes outdoor atmospheric-urban environment is needed to reproduce realistic scenarios. In this context, computational fluid dynamics (CFD) is a useful tool. To perform a precise analysis of the inhalation exposure of factory workers to potential gas-phase contaminants in the working environment (i.e., inhaled dose of contaminants and potential effects), the human body and respiratory tract need to be integrated in the analysis. Therefore, in this study, we performed an integrated occupational inhalation exposure/toxicology assessment in a factory building that applies a computer simulated person (CSP), a virtual human respiratory tract and integrated physiologically-based toxicokinetic (PBTK) model to predict tissue dosimetry distribution. Outdoor airflow variation was transported into the enclosure through an hourly change in wind pressure coefficient to calculate transient ventilation rate and indoor contaminant concentration between 08:00 and 17:00 h. Thereafter, the time-averaged contaminant concentration calculated at the nares of the human body was employed in a steady state calculation of airflow and contaminant distribution inside the virtual respiratory tract. Subsequently, we predicted adsorbed contaminant in the first layer of tissue of the human airways; highest adsorption took place in the nasal cavity. Finally, based on the results of the comprehensive coupled numerical analysis performed using the CFD-CSP-PBTK model, we quantitatively discussed differences between the inhalation exposure concentration and representative contaminant concentration in the factory space (e.g., time and volume-averaged concentration). Precise dose inhalation in the respiratory tract was calculated through an integrated analysis method using CFD, computer simulated person, virtual respiratory tract and PBTK model.