## 3 Results and Discussion
### Health Risk Assessment of PAHs and Heavy Metals in Settled House Dust
#### 3.5.2 Heavy Metal Risk Exposure in Settled House Dust  
Table 4 presents the doses of metals that children and their parents received through all the three routes of exposure, as well as the total dose. According to the results, the ingestion of house dust was found to be the main exposure pathway for metals to children, followed by dermal contact. This finding is in agreement with previously conducted studies [15,41]. The results also indicated that the doses received by the children were one or two orders of magnitude lower than those of their parents. Depending on the magnitude of exposure dose the heavy metals for both children and their parents were sorted as follows: Zn > Cu > Cr > Pb > Ni > Ni > As > Se > Cd > Hg. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Element** & \multicolumn{2}{c}{**Dingestion**} & \multicolumn{2}{c}{**D\({}_{\text{inhalation}}\)**} & \multicolumn{2}{c}{**D\({}_{\text{Dermal}}\)**} & \multicolumn{2}{c}{**D\({}_{\text{total}}\)**} \\ \hline  & **Child** & **Adult** & **Child** & **Adult** & **Child** & **Adult** & **Child** & **Adult** \\ \hline Cr & 1.00 \(\times\) 10\({}^{-3}\) & 9.32 \(\times\) 10\({}^{-5}\) & 2.11 \(\times\) 10\({}^{-8}\) & 1.30 \(\times\) 10\({}^{-8}\) & 1.15 \(\times\) 10\({}^{-6}\) & 1.40 \(\times\) 10\({}^{-7}\) & 1.00 \(\times\) 10\({}^{-3}\) & 9.33 \(\times\) 10\({}^{-5}\) \\ Ni & 4.60 \(\times\) 10\({}^{-4}\) & 4.27 \(\times\) 10\({}^{-5}\) & 9.65 \(\times\) 10\({}^{-9}\) & 5.97 \(\times\) 10\({}^{-9}\) & 5.29 \(\times\) 10\({}^{-7}\) & 6.41 \(\times\) 10\({}^{-8}\) & 4.60 \(\times\) 10\({}^{-4}\) & 4.27 \(\times\) 10\({}^{-5}\) \\ Cu & 5.22 \(\times\) 10\({}^{-3}\) & 4.85 \(\times\) 10\({}^{-4}\) & 1.10 \(\times\) 10\({}^{-7}\) & 6.78 \(\times\) 10\({}^{-8}\) & 6.00 \(\times\) 10\({}^{-6}\) & 7.28 \(\times\) 10\({}^{-7}\) & 5.22 \(\times\) 10\({}^{-3}\) & 4.85 \(\times\) 10\({}^{-4}\) \\ Cd & 8.23 \(\times\) 10\({}^{-6}\) & 7.65 \(\times\) 10\({}^{-7}\) & 1.73 \(\times\) 10\({}^{-10}\) & 1.07 \(\times\) 10\({}^{-10}\) & 9.47 \(\times\) 10\({}^{-9}\) & 1.15 \(\times\) 10\({}^{-9}\) & 8.24 \(\times\) 10\({}^{-6}\) & 7.66 \(\times\) 10\({}^{-7}\) \\ Pb & 7.09 \(\times\) 10\({}^{-4}\) & 6.58 \(\times\) 10\({}^{-5}\) & 1.49 \(\times\) 10\({}^{-8}\) & 9.20 \(\times\) 10\({}^{-9}\) & 8.15 \(\times\) 10\({}^{-7}\) & 9.88 \(\times\) 10\({}^{-8}\) & 7.09 \(\times\) 10\({}^{-4}\) & 6.59 \(\times\) 10\({}^{-5}\) \\ Zn & 6.16 \(\times\) 10\({}^{-3}\) & 5.72 \(\times\) 10\({}^{-4}\) & 1.29 \(\times\) 10\({}^{-7}\) & 8.01 \(\times\) 10\({}^{-8}\) & 7.09 \(\times\) 10\({}^{-6}\) & 8.60 \(\times\) 10\({}^{-7}\) & 6.17 \(\times\) 10\({}^{-3}\) & 5.73 \(\times\) 10\({}^{-4}\) \\ Hg & 5.79 \(\times\) 10\({}^{-6}\) & 5.38 \(\times\) 10\({}^{-7}\) & 1.22 \(\times\) 10\({}^{-10}\) & 7.53 \(\times\) 10\({}^{-11}\) & 6.66 \(\times\) 10\({}^{-9}\) & 8.08 \(\times\) 10\({}^{-10}\) & 5.80 \(\times\) 10\({}^{-6}\) & 5.39 \(\times\) 10\({}^{-7}\) \\ As & 6.08 \(\times\) 10\({}^{-5}\) & 5.64 \(\times\) 10\({}^{-6}\) & 1.28 \(\times\) 10\({}^{-9}\) & 7.89 \(\times\) 10\({}^{-10}\) & 6.99 \(\times\) 10\({}^{-8}\) & 8.47 \(\times\) 10\({}^{-9}\) & 6.08 \(\times\) 10\({}^{-5}\) & 5.65 \(\times\) 10\({}^{-6}\) \\ Se & 1.61 \(\times\) 10\({}^{-5}\) & 1.50 \(\times\) 10\({}^{-6}\) & 3.39 \(\times\) 10\({}^{-10}\) & 2.09 \(\times\) 10\({}^{-10}\) & 1.85 \(\times\) 10\({}^{-8}\) & 2.25 \(\times\) 10\({}^{-9}\) & 1.61 \(\times\) 10\({}^{-5}\) & 1.50 \(\times\) 10\({}^{-6}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Exposure to heavy metals in SHD through the different exposure pathways. According to Table 5, which presents a comparison between the total doses for children and their parents with the reference doses, the total dose of Cr for children was the same order of magnitude as the reference dose. The doses for all the other elements were found 1-2 order of magnitude lower than the corresponding reference doses.