## 2 Materials and Methods
### Pollution Indices of Soil Contamination and Potential Human Health Risk Assessment  
Because it is important to assess soil pollution and the level that heavy metal concentrations from soil can affect the human health, a descriptive analysis was performed with Microsoft Excel 2019. The analysis focused on statistical parameters that characterized the heavy metal content of the soil and the influence of contaminant concentrations on the health state of inhabitants [7]. To estimate the soil heavy metal contamination, several pollution indices were considered, such as integrated pollution index (IPI), geo-accumulation index (I\({}_{\text{geo}}\)) and enrichment coefficient (EC) [5; 17; 27; 29; 33], and risk assessment parameters [10; 12; 27; 33; 41; 42; 43; 44; 45; 46; 47; 48], synthesized in Table 1. Risk assessment was established to evaluate the possible heath impact on humans from toxic exposure. To evaluate the potential toxic effect on children playing in a given area, four paths of direct contact with the contaminants from soil were considered: ingestion (found to be the principal exposure pathway to human health), dermal contact, inhalation (fugitive soil particles) and vaporization (mercury volatilization) [41; 42; 43] in order to establish the relationship between the contaminant, pathway and receptor. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Indices** & **Information** & **Equation (No. )** & **Fulibration Classification** & **References** \\ \hline IPI & Soil contamination can be described using the integrated pollution index (PI), which is defined as the ratio between the measured concentration of heavy & IPI = \(\frac{C_{\rm{tot}}}{N}\) (1) & if the IPI value is \(<\)1, the level of pollution is low; if I \(<\)1 PI \(<\)2, there is an average level of pollution, and an IPI \(>\)2 is considered to legislation. & [5] \\ \hline \multirow{4}{*}{III\({}_{\rm{pop}}\)} & The geo-accumulation index (log) indicates the potential anthropogenic input & & If the results are smaller or equal to 0, the soil is unpolated, i.e., the soil is unpolated, i.e., and moderately polluted-1, the soil is unpolated to the following effects. & [17, 20, 33] \\  & of heavy metals into soils, C\({}_{\rm{t}}\) is the measured concentration of heavy metals in & \(\log_{\rm{t}}\)= log\({}_{\rm{t}}\)/\(\sum_{\rm{t}}\) (2) & moderately polluted-3, the soil is unpolated & [17, 20, 33] \\  & so: NV is the mean value and 1.5 is the background matrix correction factor due to the lipophilic effects. & & moderately destroyed destroyed polluted-4, the soil is strongly polluted. & [17, 21, 33] \\ \hline EC & The enrichment coefficient (BC) is a factor that is used to compare the heavy metal concentration from soil (C\({}_{\rm{tot}}\)) with the element concentration from the earth's crust (C\({}_{\rm{const}}\)), establishing the level of anthropogenic input. & EC \(<\) 1 indicates there is no rain insignificant enrichment while a value is 1.5 considered to show enrichments from different sources. & [17, 22, 33] \\ \hline EDD\({}_{\rm{tot}}\) & The opening of children that are playing on playgrounds and plans to transport & EDD\({}_{\rm{tot}}\) = \(\frac{C_{\rm{tot}}+\log_{\rm{t}}+\log_{\rm{t}}}{N}\)\(>\) 1 \(\times\) 4 (6) & & \\ \hline EDD\({  
To assess the non-carcinogenic risk due to heavy metal exposure from soil collected from parks, we calculated the estimated daily intakes (EDIs) for Sr, Rb, Cu, As, Ni, Zn, Zr, V, Cd, Ag and Hg according to USEPA standards, as seen in Tables 1 and 2[14; 17; 42; 44; 45]. The potential non-cancer risks to children's health were evaluated by calculating the hazard quotient (HQ), which represents the non-carcinogenic risk due to the exposure to heavy metals from soil with reference to EDI and the reference dose (RfD) [10; 12; 27]. RfD (mg kg\({}^{-1}\) day\({}^{-1}\)), found in Table 3, is considered to be the maximum daily dose from a specific heavy metal from a specific pathway that will not affect the health of a sensitive adult or child body, throughout a lifetime [17; 42; 47; 48; 50].