2.7.1. Exposure Assessment

To calculate the human exposure dose, the average daily intake (*ADI*) of heavy metals in soil for three exposure pathways (ingestion, inhalation, and dermal contact) is calculated as follows:

*Ingestion pathway:*

$$ADD\_{\text{ingestion}} = \frac{\mathcal{C} \times IR\_{\text{ig}} \times EF \times ED \times CF}{BW \times AT} \tag{2}$$

*Inhalation pathway:*

$$ADD\_{inhalation} = \frac{C \times IR\_{i\hbar} \times EF \times ED}{BW \times AT \times PEF} \tag{3}$$

*Dermal contact pathway:*

$$ADD\_{\text{dermal contact}} = \frac{\mathbb{C} \times SA \times SAF \times DAF \times EF \times ED \times CF}{BW \times AT} \tag{4}$$

where *ADIingestion*, *ADIinhalation*, *ADIdermal contact* is the average daily intake (mg/kg day) via ingestion, inhalation, and dermal contacts, respectively. *C* is the concentration of analyzed heavy metals in soil samples (mg/kg); *IRig* is the ingestion rate (100 and 200 mg/day for adults and children, respectively) [28,45,48]; *IRih* is the inhalation rate (12.8 m3/day for adults and 7.63 m3/day for children) [28]; *EF* is the exposure frequency (365 days/year) [28,45]; *ED* is the exposure duration (30 years for adults and 6 years for children) [28]; *CF* is the conversion factor for soil (10−<sup>6</sup> kg/mg) [48]; *BW* is the body weight (70 and 20 kg for adults and children, respectively) [28]; *AT* is the average exposed time (*EF* × *ED*) [28]; PEF is the particulate emission factor (1.36 × 10<sup>9</sup> m<sup>3</sup> /kg) [28]; *SA* is the skin exposed area for soil (4350 and 1600 cm<sup>2</sup> for adults and children, respectively) [28]; *SAF* is the skin adherence factor (0.7 mg/cm<sup>2</sup> for adults and 0.2 mg/cm<sup>2</sup> for children) [28,48]; and *DAF* is the dermal absorption factor (0.001) [28].

## 2.7.2. Non-Carcinogenic Risk Assessment

The hazard quotient (*HQ*) is characterized for non-carcinogenic hazards and is defined as the average daily intake by the toxicity threshold value, which is referred to as the chronic reference dose (*RfD*) in mg/kg-day of the specific heavy metal. *HQ* is computed as the ratio of the average daily intake (*ADI*) and a reference dose (*RfD*). The equitation of *HQ* is given as follows [28,45]:

$$HQ = \frac{ADI}{RfD} \tag{5}$$

where *HQ* is the hazard quotient, *ADI* is the average daily intake (mg/kg day) and *RfD* is the reference dose (mg/kg day) of heavy metals via ingestion, inhalation, and dermal contact pathways. The reference dose (*RfD*) of studied heavy metals is shown in Table S2.

Hazard index (*HI*) is a cumulative non-cancer health risk that can be evaluated by the sum of the *HQ* (hazard quotient) values of various exposure pathways. It can be calculated as the sum of non-carcinogenic hazard quotients for all contaminants [45] as follows:

$$HI = \sum \dot{H} \mathbf{Q} \dot{\mathbf{r}} \tag{6}$$

where *HQi* is the non-cancer hazard quotient for the ith contaminants.

*HI* < 1 indicated no non-carcinogenic health, whereas *HI* > 1 risk indicated adverse non-carcinogenic health risk [28,49].

## 2.7.3. Carcinogenic Risk Assessment

The carcinogenic risk assessment is the incremental probability of an individual developing cancer over a lifetime as a result of exposure to the potential carcinogen like heavy metals [27,50]. Carcinogenic risk and total carcinogenic risks are determined as follows:

$$\mathcal{CR} = ADI \times \mathcal{SF} \tag{7}$$

$$T\mathbb{C}R = \sum \mathbb{C}R\tag{8}$$

where *CR* is the carcinogenic risk; *ADI* is the average daily intake (mg/kg day); *SF* is the cancer slope factor over a lifetime (mg/kg day). The cancer slope factor (*SF*) of studied heavy metals is shown in Table S2.

The values of carcinogenic risk (*CR*) ranging from 1 × 10−<sup>6</sup> to 1 × 10−<sup>4</sup> are considered as safe limit for human health [28,45], whereas higher *CR* values than the limit of 1 × 10−<sup>4</sup> cause lifetime cancer risks to the human body [45,49].
