## 3 Results and Discussion
### Risk Assessment
#### 3.2.2 Human Health Risk Assessment (HHRA)  
The main objective of the human health risk analyses was to gain the first impression of the total risk value, arising from the possible contact with roof runoff. Thus, the element contents after acid digestion (Table 3) were chosen to calculate the highest possible risk value according to the rule of the most conservative risk assumptions. As regards carcinogenic elements, only Pb was analyzed with respect to the existing toxicological parameters and determined element contents. The values of calculated average daily doses in the ingestion exposure pathway and of dermal absorbed doses in the dermal contact exposure pathway are presented in Table S6. The values of calculated carcinogenic and non-carcinogenic risk, as well as of the total risk, are presented in Table 5. The total non-carcinogenic risk values exceeded the acceptable level of one both in adults (HQ = 1.38) and children (HQ = 2.52). The pathway of dermal contact exposure to roof runoff had a dominant impact on the risk value in non-carcinogenic risk. In that exposure pathway, the decreasing risk of the investigated elements was found to be as follows: Pb > Cu > Mo > Co > Ni > Al > Fe > Mn > Zn > Ba. In the ingestion exposure pathway, the decreasing risk of the analyzed elements was ordered as follows: Ni > Pb > Zn > Co > Fe > Mn > Cu > Mo > Al > Ba. In the cases of individual carcinogenic elements, the acceptable level of \(1\times 10^{-6}\) for Pb was exceeded in the dermal contact exposure pathway (adults CR = \(4.87\times 10^{-5}\), children CR = \(2.23\times 10^{-5}\)). Dermal contact was a dominant exposure pathway, in comparison to accidental ingestion of roof runoff. The results of health risk analysis indicated that both non-carcinogenic and carcinogenic risk values for investigated compounds exceeded the acceptable levels which suggests that contamination of rainfall water in urban agglomerations becomes an environmental threat that was confirmed in our risk assessment calculations for the dermal contact exposure pathway. Thus, it should be taken into account by residents of urban areas when planning a walk outside. However, pollutant contents taken for calculations referred to contents of roof water  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Parameter** & **Toxicity Potential (TP)** & **Contamination Factor (CP)** \\ \hline Bacteria & - & 0.26 \\ Fungi & - & 0.24 \\ pH & \textless{}1 & 0.91 \\ EC & - & 0.46 \\ Cl- & 0.007 & 0.34 \\ N-NO3 & 0.03 & 0.40 \\ P-PO4 & - & 0.28 \\ SO42- & - & 0.23 \\ SiO2 & - & 0.53 \\ Ag & - & 0.26 \\ Al & 0.05 & 0.27 \\ Ba & 0.002 & 0.28 \\ Ca & - & 0.27 \\ Cu & 0.005 & 0.28 \\ Fe & 0.03 & 0.47 \\ Hg & - & 0.27 \\ K & - & 0.29 \\ Mg & - & 0.46 \\ Mn & 0.06 & 0.41 \\ Mo & 0.08 & 0.22 \\ Na & - & 0.50 \\ Ni & 0.03 & 0.63 \\ Pb & 0.18 & 0.34 \\ Zn & 0.14 & 0.24 \\ \hline \hline \multicolumn{3}{l}{Contamination degree (Cdeg)} & 9.44 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Ecological risk values of roof runoff in Kraków.  
runoff, and thus they were not precisely the content in rainwater. Notwithstanding, according to conservative risk assessment principle, the worst case scenario was assessed.