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Polycyclic aromatic hydrocarbons (PAHs) are widely distributed throughout the atmosphere as mixtures attached to ambient particulate matter (PM). PAHs usually elicit similar toxicological pathways but do so with varying levels of efficacy. In this study, we utilized high-throughput screening (HTS) in vitro data of PAHs to predict health risks associated with coarse and fine PM. PM samples with 22 PAH compounds obtained from residential areas close to industrial parks in central Taiwan were analyzed. On the basis of the PM-bound PAH concentrations and their activities reported in HTS assays, we developed a probabilistic model for estimating cumulative exposure of humans to PAHs. Activity-to-exposure ratio (AER) values were calculated to compare relative risks of activating the aryl hydrocarbon receptor (AhR), nuclear factor erythroid 2-related factor 2 (Nrf2), and tumor suppressor gene (p53) when children or adults were exposed to fine or coarse PM in different seasons. On the basis of AER values, the risk of fine PM exposure was relatively higher than the risk of exposure to coarse PM in pathway activation. Children as a susceptible population had a risk of the activating AhR pathway greater than that of adults. Particularly higher risks were observed in winter than in summer. Among three pathways, AhR was the most sensitive one activated by exposure to PAHs. In addition, the activation of the AhR, Nrf2, and p53 pathways was compared by in vitro reporter assays with and without the pre-extraction of PAHs from PM. Our proposed novel approach accounts for mixture toxicities in characterizing in vitro pathway-based risks via inhalation exposure to ambient PAHs.