## 3 Results and Discussion
### Health Risk Assessment  
The relative health risks caused by the endocrine-disrupting activities of atmospheric PAHs and OH-PAHs were evaluated using the relative estrogenic and antiestrogenic activities and binding affinities to hER\(\alpha\), which were reported by [PERSON] et al. (2018). None of the PAHs showed any estrogenic and antiestrogenic activities in the previous study. Therefore, only the estrogenic and antiestrogenic activities of the OH-PAHs were analyzed in the present study. The total estrogenic and total antiestrogenic activities showed general trends of higher levels in winter and lower levels in summer, as was the case for the atmospheric concentrations. Four-ring PAH derivatives, such as OH-Chrysene and OH-benz[_a_]anthracene, had particularly high health risks. The calculated, relative, estrogenic activities of the atmospheric OH-PAHs are shown in Figure 5. The total estrogenic activity was highest in winter 2018 (1.58 \(\pm\) 0.43), followed by autumn 2017 (1.16 \(\pm\) 0.72), spring 2017 (1.12 \(\pm\) 0.66), spring 2018 (0.70 \(\pm\) 0.44), and summer 2017 (0.28 \(\pm\) 0.12). The total estrogenic activity in summer was significantly lower than that in spring 2017 (\(p\) = 0.04), autumn 2017 (\(p\) = 0.03), and winter 2018 (\(p\) < 0.01), and that in winter 2018 was significantly higher than that in spring 2018 (\(p\) = 0.03). Because of the higher activity of the four-ring OH-PAHs (2018), the activities of 2/3 OH-Chr and 6 OH-Chr/3 OH-BaA were dominant in the total activity (72.7 \(\pm\) 5.6%). In particular, 2/3 OH-Chr showed high proportions in all samples (53.6 \(\pm\) 12.9%). 2 OH-Nap was dominant for the total concentration (20.1 \(\pm\) 11.7%); however, it has low estrogenic activity (0%). The second most dominant component, in terms of total concentration, was 2/3 OH-Phe (16.5 \(\pm\) 3.0%), and it had a similar contribution to total estrogenic activity (16.7 \(\pm\) 3.7%). The compound 1 OH-Pyr had a low contribution to total estrogenic activity (6.3 \(\pm\) 1.5%), although it appears consistently in all seasons. The calculated, relative, antiestrogenic activities of atmospheric OH-PAHs are shown in Figure 6. Unlike with estrogenic activity, only OH-PAHs with four rings were antiestrogenic (2018). Therefore, only 2/3 OH-Chr and 6 OH-Chr/3 OH-BaA had health risks (78.6 \(\pm\) 16.7% and 21.4 \(\pm\) 16.7%, respectively). Similar to estrogenic activity, the total antiestrogenic activity was highest in winter 2018 (1.02 \(\pm\) 0.27), followed by spring 2017 (0.72 \(\pm\) 0.41), autumn 2017 (0.71 \(\pm\) 0.40), spring 2018 (0.43 \(\pm\) 0.26), and summer 2017 (0.20 \(\pm\) 0.08). The differences in total antiestrogenic activity among the seasons was the same as that for the estrogenic activity. In addition, the total estrogenic activity and total antiestrogenic activity were significantly correlated (\(p\) < 0.01, \(r\) = 0.985). Figure 4: Correlation between the atmospheric concentrations of the target compounds and PM\({}_{2.5}\): (**a**) total PAHs versus PM\({}_{2.5}\), and (**b**) total OH-PAHs versus PM\({}_{2.5}\). Among the OH-PAHs, OH-chrysenes and OH-benz[\(a\)]anthracene had small contributions to the total concentration (9.8-26.1%). However, their high contributions to estrogenic activity (57.1-83.1%) and antistrogenic activity (100%) suggest that they pose relatively high health risks for humans. The current results indicated that the health risks of endocrine disruption caused by atmospheric OH-PAHs are higher in the winter than in summer. The binding potentials of PAHs and OH-PAHs to hER calculated from the reported binding affinities are shown in Figure 7. Several PAHs (BbF, BkF, BaP, BgPe, and IDP) and OH-PAHs (1/2 OH-Nap, 1/3 OH-Flu, 1/4/9 OH-Phe, and 3 OH-BaP) were considered to have no binding potential. Similar to the estrogenic and antistrogenic activities, 2/3 OH-Chr had the highest contribution to the total estimated binding potential (26.1 \(\pm\) 5.5%), followed by 2/3 OH-Phe (19.5 \(\pm\) 4.2%).