## 4 Conclusions  
High PM10 concentrations were observed at the roadside (56.4 \(\pm\) 27.3 \(\mathrm{\SIUnitSymbolMicro g}\) m\({}^{-3}\)) and industrial (51.0 \(\pm\) 31.1 \(\mathrm{\SIUnitSymbolMicro g}\) m\({}^{-3}\)) sites in the Bangkok Metropolitan Administration. PM10-bound PAHs were quantified, and the associated carcinogenic health risks were estimated. PM10 and pPAH measurements made over a one-year period indicated high concentrations of PAHs during dry and cool winter conditions. In contrast, PM10 and most pPAH concentrations were significantly lower in the hot and humid summer period than during other seasons. Seasonal variations of pPAHs result in higher average total carcinogenicity during the winter, possibly as a result of higher particulate concentrations and less photochemical degradation. Carcinogenic four- to six-ring PAHs were major components of overall pPAH composition. BaP accounted for approximately 60% and 40% of total carcinogenicity at the roadside and urban background sites, respectively, and 40% of total carcinogenicity at the industrial site. The profile of relative concentrations of PAHs was markedly different at the industrial site, resulting in the highest average total carcinogenicity of 0.83 ng m\({}^{-3}\) BaP-TEQ. The average total carcinogenicity was lowest at the urban background site (0.39 ng m\({}^{-3}\) BaP-TEQ). The average BaP concentrations were below the published EC limit (1 ng m\({}^{-3}\)). The lifetime BaP-TEQ lung cancer risks estimated from concentrations at all sampling sites were 0.16 to 1.4 cancer cases per million people, with higher estimated health risks in roadside and industrial areas. Although concentrations of PM10-bound PAHs were within the published EC limit, PM10 concentrations were almost three times higher than the published WHO guideline. These observations provide quantitative exposure estimates to help inform future Thai national air pollution standards and policy, including potential for a reduction in carcinogenic health risks from exposure to pPAHs that could result from a reduction in PM10 pollution, particularly during the winter. The following are available online at [[https://www.mdpi.com/article/10.3390/app11104501/s1](https://www.mdpi.com/article/10.3390/app11104501/s1)]([https://www.mdpi.com/article/10.3390/app11104501/s1](https://www.mdpi.com/article/10.3390/app11104501/s1)), Table S1: Meteorological parameters, seasonal and annual concentrations of PM\({}_{10}\) (\(\mathrm{\SIUnitSymbolMicro g}\) m\({}^{-3}\)) and PAHs (ng m\({}^{-3}\)). Table S2: Concentrations of PM\({}_{10}\) (\(\mathrm{\SIUnitSymbolMicro g}\) m\({}^{-3}\)) and BaP (ng m\({}^{-3}\)) in different countries. Table S3: Annual mean pPAHs concentrations, BaP-TEQ concentrations and percentage of BaP-TEQ concentrations. Figure S1: Daily mean concentrations of BaP (ng m\({}^{-3}\)) at the roadside, industrial and urban background sites compared with the EC (1 ng m\({}^{-3}\)) and UK (0.25 ng m\({}^{-3}\)) annual average guidelines. Figure S2: Dominant wind directions for each site in each of the 3 seasons. No statistical relationship between the wind patterns and the PAHs measured were found. Figure S3: Linear correlation plots between PM10 vs. total PAHs from whole year data. Figure S4. Seasonal correlation plots between PM10 and total PAHs concentrations in the wet season (R) and cool-dry season (W) at the three sampling sites. Figure S5a: Time series plot of daily mean PM\({}_{10}\) (\(\mathrm{\SIUnitSymbolMicro g}\) m\({}^{-3}\)) and PAHs (ng m\({}^{-3}\)) concentrations at the roadside site. (Missing data indicted sampling failures where PM\({}_{10}\) filters were not collected.) Figure S5b: Time series plot of daily mean PM\({}_{10}\) (\(\mathrm{\SIUnitSymbolMicro g}\) m\({}^{-3}\)) and PAHs (ng m\({}^{-3}\)) concentrations at the industrial site. (Missing data indicted sampling failures where PM\({}_{10}\) filters were not collected.)