## 2 Materials and Methods
### Health Risk Estimation  
BaPE is the first parameter to estimate carcinogenicity of total PAHs. BaPE values above 1.0 ng m\({}^{-3}\) represent an increased cancer risk. BaPE is calculated according to Equation (1):  
\[\text{BaPE }=\left(\left[\text{BaA}\right]\ast 0.06\right)\ +\ \left(\left[\text{BbF}\right]\ast 0.07 \right)\ +\ \left(\left[\text{BkF}\right]\ast 0.07\right)\ +\ \left(\left[\text{BaP}\right]\ast 1\right)\ +\ \left(\left[\text{DBA}\right]\ast 0.6\right) \tag{1}\]  
Total carcinogenic and mutagenic potential of particulate bound PAHs, \(\Sigma\text{BaP}_{\text{TEQ}}\) and \(\Sigma\text{BaP}_{\text{MEQ}}\), were calculated as described elsewhere [40; 41; 42], using Equations (2) and (3):  
\[\Sigma\text{BaPTEQ }= \Sigma\{\left(\left[\text{BaA}\right]\ast 0.1\right)+\ \left(\left[\text{CHK}\right]\ast 0.01\right)+\ \left(\left[\text{BbF}\right]\ast 0.1\right)+\ \left(\left[\text{BkF}\right]\ast 0.1\right) \tag{2}\] \[\ \ \ \ +\left(\left[\text{BaP}\right]\ast 1\right)+\ \left(\left[\text{ IPY}\right]\ast 0.1\right)+\ \left(\left[\text{DBA}\right]\ast 5\right)+\ \left(\left[\text{BPE}\right]\ast 0.01 \right)\}\]  
\[\Sigma\text{BaPMEQ }= \Sigma\{\left(\left[\text{BaA}\right]\ast 0.082\right)+\ \left(\left[\text{CHK}\right]\ast 0.017\right)+\ \left(\left[\text{BbF}\right]\ast 0.25\right)+\ \left(\left[\text{BkF}\right]\ast 0.11\right) \tag{3}\] \[\ \ \ \ +\left(\left[\text{aP}\right]\ast 1\right)+\ \left(\left[\text{IPY}\right]\ast 0.31\right)+\ \left(\left[\text{DBA}\right]\ast 0.29\right)+\ \left(\left[\text{BPE}\right]\ast 0.19\right)\}\]The relation between exposure and cancer risk is considered linear in low doses, and thus inhalation cancer risk associated to PAHs could be calculated from \(\Sigma\)BAP\({}_{\text{TEQ}}\) using the inhalation unit risk (IUR\({}_{\text{BaP}}\)= \(1.1\times 10^{-3}\) (\(\mu\)g m\({}^{-3}\))\({}^{-1}\)[43] for BaP and according to the following equation (Equation (4)):  
\[\text{ICR}=\ \Sigma\text{BaPTEQ}*\ \text{IURBaP} \tag{4}\]  
In general, exposure to toxic substances in the ambient air depends on the chronic daily intake (CDI) of each pollutant emitted by the source. CDI (mg/kg/day) could be calculated as Life Averaged Daily Dose (LADD) using Equation (5) [43; 44; 45]:  
\[\text{CDI}=\text{Cair}*IF \tag{5}\]  
where Cair is concentration of pollutant (mg m\({}^{-3}\)), and IF is Intake Factor (mg\({}^{3}\)/kg/day) derived from Equation (6):  
\[IF=\frac{IR*EF*ED*ET}{BW*AT} \tag{6}\]  
where according to EPA (1998) Inhalation Rate (\(IR\)) = 20 m\({}^{3}\)/day; Exposure Frequency (\(EF\)) = 365 days; Exposure Duration (\(ED\)) = 70 years; Exposure Time (\(ET\)) = 24 h/day; Body Weight (\(BW\)) = 70 kg; and Average Time (\(AT\)) = 35,500 days for exposure to carcinogenic pollutants. Cancer risk of the specific substances like POPs is calculated using Equation (7):  
\[\text{Cancer Risk}=\ \text{LADD}*SF \tag{7}\]  
where Slope Factor (\(SF\)) (mg/kg\(\cdot\)day)\({}^{-1}\) values were calculated by Equation (8):  
\[SF=\frac{\text{IUR m}^{3}\mu\text{g}-1\ \times\ 70\ \text{kg}\times 103\ \mu\text{g}\ \text{mg}-1}{20\ \text{m}^{3}\ \text{day}-1} \tag{8}\]  
Inhalation Unit Risk values used for the estimation of Cancer Risk by each PCDD/Fs, PCBs, and PAHs were obtained from OEHHA [46]. Cancer risk values in our study were compared to upper-bound cancer risk of \(1\times 10^{-6}\) (one person per million could develop cancer from the inhalation of this pollutant). Cancer risk values over this benchmark level are considered significant, and risks over \(1\times 10^{-4}\) are unacceptable by EPA (2012). Finally, a total risk related to the sampling site was calculated, summarizing the risk from each pollutant.