## 3 Results and Discussion
### Carcinogenicity of PM10-Bound PAHs  
Toxicity equivalency factors (TEF) of 13 PAHs proposed by [PERSON] (1998) [PERSON] (1998) were selected for the calculation of BaP-TEQ concentrations of pPAHs. Annual mean concentrations of 13 PAHs and total BaP-TEQ concentrations are summarized in the Supplementary Information (Table S3). While the total PAH and BaP concentrations were highest at the roadside site, the highest BaP-TEQ concentration was found at the industrial site, emphasizing the importance of PAH compositions. DBA possessing a higher TEF than BaP plays an important role in the total carcinogenicity of pPAHs at the industrial site. Therefore, speciation of PAHs is essential in evaluating the carcinogenic risk posed by exposure to particulate-bound PAHs. The total BaP-TEQ concentrations were determined to be 0.83, 0.72 and 0.39 ng m\({}^{-3}\) at the industrial, roadside and urban background sites, respectively. A previous study estimating BaP-TEF using Nisbet and LaGoy (1992) Nisbet and LaGoy (1992) (Nisbet and LaGoy, 1992) proposed that the TEF in both gas and particulate phases of traffic PAHs in Thailand was at 3.73 ng m\({}^{-3}\)Nisbet and LaGoy (1992). Our study showed that pPAH concentrations at the roadside site were lower than previously reported from 1999 to 2000 (Nisbet and LaGoy, 1992; Nisbet and LaGoy, 1992). Levels of BaP-TEQ in the BMA measured from 2013 to 2014 were comparable with BaP-TEQ in the metropolitan area of Curitiba, Brazil, which ranged between 0.45 and 0.69 ng m\({}^{-3}\)[PERSON] and [PERSON] (1992). The [PERSON] et al. (2011) [PERSON] and [PERSON] (1992) study reported estimated lung cancer risks between 8.16 \(\times\) 10\({}^{-9}\) to 1.38 \(\times\) 10\({}^{-8}\) using the CSF value of 3.14 kg mg\({}^{-1}\) d\({}^{-1}\). Time series plots of BaP, BaP-TEQ and PM10 at three sites are shown in Figure 5. BaP and BaP-TEQ concentrations appeared to fluctuate in a similar manner at both the roadside and urban background sites, with higher concentrations at the roadside site. The highest BaP-TEQ concentrations were found in the rainy season at the roadside and urban background sites. Although the highest BaP concentration was found in the rainy season at the industrial site, the highest BaP-TEQ concentration was observed in the winter, with the highest PM10 concentration. BaP-TEQ to BaP concentration ratios were 1.7, 1.8 and 2.6 at the urban background, roadside and industrial sites, respectively. The highest proportion of BaP-TEQ/BaP ratio was found to be 3.4 at the industrial site in winter. Although BaP is the most studied PAHs in terms of carcinogenicity, previous studies showed different toxicity values, implying some discrepancy in the risk assessment [PERSON] and [PERSON] (1992); [PERSON] and [PERSON] (1992). It is shown that BaP is responsible for approximately 60% of pPAH carcinogenicity at the roadside and urban background sites in the BMA. The PAHs profile at the industrial site resulted in a higher contribution from DBA (33% of pPAH carcinogenicity) and lower contribution of BaP (42% of pPAH carcinogenicity). Therefore, the BaP toxic equivalent should be considered when evaluating human health risk posed by exposure to the ambient PAHs mixture. Incremental lifetime cancer risks were calculated from exposure concentrations in three study areas to illustrate the carcinogenic risk associated with long-term pPAH exposure. Lifetime lung cancer risks estimated from IUR were slightly higher than those estimated from CSF (Table 3). ILCR of ambient PM10-bound PAH exposure calculated in resident adults ranging between 1.6 \(\times\) 10\({}^{-7}\) to 1.4 \(\times\) 10\({}^{-6}\) were within the 1/1,000,000 threshold. However, it is important to further investigate both the gas-phase and particulate-phase PAHs to assure that the risk level is acceptable. Figure 5: Time series data showing concentrations of PM10 (\(\mathrm{\SIUnitSymbolMicro g}\) m\({}^{-3}\)), and BaP & BaP-TEQ (\(\mathrm{ng}\) m\({}^{-3}\)) at the roadside, industrial and urban background sites in the BMA.