## 2 Methodology
### Pollution Estimation and Risk Assessment
#### 2.3.3 Human Health Risk Assessment  
A variety of preventative methods have been developed to evaluate the health risks caused by contaminants in order to maintain public health. The potential human health risk models raised by the US EPA, which include carcinogenic and non-carcinogenic risks [80], have proven successful and have been used globally [5; 13; 52; 74; 81]. The direct exposure of children and adults to PETs through soils was taken into account when calculating the human health risk. The Equations. below were used to calculate chronic daily intake (CDI) of PTEs exposure ingestion (CDIingestion), inhalation (CDI inhalation), and dermal contact (CDIdermal) [74]. The exposure factors for health risk assessment mentioned in the following Equations. are listed in Table 1.  
\[\text{CDI}_{\text{ingestion}}=\frac{\text{C}\times\text{IngR}\times\text{EF} \times\text{ED}\times\text{CF}}{\text{BW}\times\text{AT}} \tag{6}\]  
\[\text{CDI}_{\text{inhalation}}=\frac{\text{C}\times\text{InhR}\times\text{EF} \times\text{ED}}{\text{PEF}\times\text{BW}\times\text{AT}} \tag{7}\]  
\[\text{CDI}_{\text{dermal}}=\frac{\text{C}\times\text{SA}\times\text{AF} \times\text{ABF}\times\text{EF}\times\text{ED}\times\text{CF}}{\text{BW}\times \text{AT}} \tag{8}\]  
Non-carcinogenic hazards are typically characterized by the hazard quotient (HQ). The HQ is defined as the quotient of the chronic daily intake divided by the toxicity threshold value, which is referred to as the reference dose (R\({}_{\text{f}}\)D) of a specific PTE. The HQ of a single PTE is determined by Equation (9). Equation (10) was used to analyze the health risk related to PTE exposure for carcinogenic risk [80]. The R\({}_{\text{f}}\)D and slope factor (SF) through each PTE exposure route are listed in Table 2.  
\[\text{HQ}_{i}=\frac{\text{CDI}_{i}}{R_{f}D_{i}} \tag{9}\]  
\[\text{CR}_{i}=\text{CDI}_{i}\times\text{SF}_{i} \tag{10}\]  
where the subscript \"i\" in Equations (9) and (10) indicate the three main PTE intake routes: ingestion, inhalation, and dermal contact. Only As, Cd, Cr, Ni, and Pb were calculated for the carcinogenic risk of the SF is given. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & **Explanation** & \multicolumn{2}{c}{**Value**} & **Units** & **Reference** \\ \cline{3-5}  & & **Adults** & **Children** & & \\ \hline C & The total concentration of the PTE & & mg/kg & \\ IngR & Ingestion rate of soil & 100 & 200 & mg/day & [74] \\ InhR & Inhalation rate of soil & 20 & 7.63 & m\({}^{3}\)/day & [74] \\ EF & Exposure frequency & 350 & 350 & day/year & [74] \\ ED & Exposure duration & 24 & 6 & year & [74] \\ BW & Body weight & 70 & 20 & kg & [82] \\ AT\({}_{\text{nc}}\) & The average time (non-carcinogenic risk) & \(365\times 24\) & \(365\times 6\) & days & [74] \\ AT\({}_{\text{c}}\) & The average time (carcinogenic risk) & \(365\times 70\) & \(365\times 70\) & days & [81] \\ PEF & Particle emission factor & \(1.36\times 10^{9}\) & \(1.36\times 10^{9}\) & m\({}^{3}\)/kg & [74] \\ SA & Surface area of the skin that contacts the PTEs & 4350 & 1600 & cm\({}^{2}\) & [74] \\ AF & Skin adherence factor & 0.7 & 0.2 & mg/cm\({}^{2}\) & [74] \\ ABF & Dermal absorption factor & 0.001 & 0.001 & - & [74] \\ CF & Conversion factor & \(10^{-6}\) & \(10^{-6}\) & - & [74] \\ \hline \hline \end{tabular} Note: In the case of Cr, \(1/6\) of the total concentration was used in the risk calculations for both non-carcinogenic and carcinogenic risk [83; 84].  
\end{table} 
Table 1: Exposure factors for human health risk assessment. For an individual PTE in soil, the possible non-carcinogenic and carcinogenic risks are expressed as the hazard index (HI) and total cancer risk (TCR). HI is the sum of the HQ of an individual PTE through the three intake routes. TCR is the sum of the CR through the three intake routes. The Equations.