A new approach for risk assessment of pulmonary toxicants: a preliminary study using didecyldimethylammonium chloride

Abstract

Recently, interest in alternative toxicity testing methods to reduce the number of animals used in toxicity evaluations has increased. A more accurate approach is required for human risk assessments, which currently uses animal toxicity data to determine point of departure (POD) values and applies uncertainty factors. Therefore, in this study, we propose an approach for an inhalation toxicity risk assessment using in silico and in vitro methods. Human primary alveolar epithelial cells were treated with aerosolized didecyldimethylammonium chloride (DDAC) to determine cytotoxicity, then transcriptome analysis and biological pathway investigation was combined based on adverse outcome pathways (AOPs) to calculate the POD. Human DDAC exposure was simulated using a multiple-path particle dosimetry (MPPD) model to predict the exposure level of human alveolar area to inhalation of DDAC in silico. These in silico and in vitro results were compared, and a risk assessment was performed. The POD for oxidative stress, inflammation, EMT, apoptosis, and autophagy, which are key AOP452 events, were between 19.0 and 23.89 ng/cm2 according to benchmark dose calculation tools. The human exposure to DDAC in alveolar epithelial cells was 0.164 ng/cm2/day, resulting in a margin of exposure (MOE) range of 121–145. This study proposes a novel risk assessment method that involves comparing the exposure of human lung alveolar epithelial cells through inhalation using the human equivalent concentration method through in vitro experiments. This study demonstrated that it is possible to perform human risk assessments using both in silico and in vitro methods.