## 3 Results and Discussion
### Associations between Ambient PAH and Cough  
The analysis of the association between daily PAH concentrations and cough results using the GEE is shown in Table 4. After adjusting for potential confounders, including SO\({}_{2}\), NO\({}_{2}\), and PM\({}_{2.5}\), a positive association was found between BaA levels and cough in the lag 4 model [B: 8.407, 95% confidence interval (CI): 1.260-15.554] and lag 5 model (B: 9.406, 95% CI: 0.678-18.134) among the lag 0 to lag 5 models, and a similar trend was observed in cases of Pyr and BghiP, while total PAH and TSP levels were not associated with cough. Previous studies have found that exposure to specific PAHs, including BaA, is associated with adverse respiratory outcomes. Serum BaA levels were associated with childhood asthma biomarkers, including resistin and IgE, as well as interleukin-10 [27] in a pediatric case-control study. Urine 1-hydroxypyrene levels were associated with childhood asthma [28] in another case-control study. Furthermore, a recent case-control adult study demonstrated that 2-hydroxyfluorene, 1- and 4-hydroxyphenanthrene, and 1-hydroxypyrene concentrations were associated with a greater adult asthma exacerbation risk among 12 urinary PAHs metabolites [29]. These findings, including the present study, suggested that low-molecular-weight PAHs, including BaA, are associated with respiratory diseases with chronic cough both in children and adults. Figure 1: The course of the concentrations of total PAH and TSP in Kanazawa and Fukuoka during the study period. PAH, polycyclic aromatic hydrocarbons; TSP, total suspended particles. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & \multicolumn{2}{c}{**Kanazawa**} & \multicolumn{2}{c}{**Fukuoka**} & \multicolumn{1}{c}{\(p\) **Value**} \\ \cline{2-6}  & **Mean** & **SD** & **Mean** & **SD** & **\(p\) **Value** \\ \hline Total PAHs (ng/m\({}^{3}\)) & 0.264 & 0.146 & 0.523 & 0.343 & **\textless{}0.001** \\ Flt (ng/m\({}^{3}\)) & 0.053 & 0.037 & 0.100 & 0.084 & **\textless{}0.001** \\ Pyr (ng/m\({}^{3}\)) & 0.046 & 0.025 & 0.082 & 0.056 & **\textless{}0.001** \\ Ba(ng/m\({}^{3}\)) & 0.007 & 0.002 & 0.013 & 0.008 & **\textless{}0.001** \\ Chr (ng/m\({}^{3}\)) & 0.024 & 0.015 & 0.059 & 0.042 & **\textless{}0.001** \\ BBF (ng/m\({}^{3}\)) & 0.036 & 0.020 & 0.082 & 0.059 & **\textless{}0.001** \\ BKF (ng/m\({}^{3}\)) & 0.012 & 0.007 & 0.026 & 0.019 & **\textless{}0.001** \\ BaP (ng/m\({}^{3}\)) & 0.018 & 0.011 & 0.039 & 0.029 & **\textless{}0.001** \\ BgbitP (ng/m\({}^{3}\)) & 0.039 & 0.019 & 0.062 & 0.034 & **\textless{}0.001** \\ lcdP (ng/m\({}^{3}\)) & 0.027 & 0.014 & 0.051 & 0.032 & **\textless{}0.001** \\ TSP (ug/m\({}^{3}\)) & 23.016 & 12.360 & 15.946 & 7.531 & **\textless{}0.001** \\ PM\({}_{2.5}\) (mg/m\({}^{3}\)) & 6.557 & 3.699 & 12.426 & 4.166 & **\textless{}0.001** \\ SO\({}_{2}\) (ppb) & 0.330 & 0.473 & 1.330 & 0.926 & **\textless{}0.001** \\ NO\({}_{2}\) (ppb) & 2.460 & 0.976 & 8.570 & 3.294 & **\textless{}0.001** \\ \hline \hline \end{tabular} SD, standard deviation. \(p\) values less than 0.05 are highlighted in bold. PAH, polycyclic aromatic hydrocarbons; Flt, fluoranthene; Pyr, pyrene; BaA, benz\(d\)[anthracene; Chr, chrysene; BBF, benzo[b]fluoranthene; BkF, benzo[b]fluoranthene; BaI, benzo[d]pyrene; BghiP, benzo[ghi]perylene; lcdP, indenol[1,2,3-cd]pyrene; TSP, total suspended particles; PM\({}_{2.5}\), particulate matter with diameters 2.5 \(\upmu\)m and smaller; SO\({}_{2}\), sulfur dioxide; NO\({}_{2}\), nitrogen dioxide.  
\end{table} 
Table 3: Concentrations of PAHs and other air pollutants in Kanazawa and Fukuoka between April and May 2020. The present finding that the association between atmospheric BaA and cough symptoms was significant in the lag 4 and lag 5 models of GEE analysis might be important in considering the mechanisms underlying the association between PAHs, particularly BaA, and chronic cough.