## 3 Results and Discussion
### Risk Assessment
#### 3.2.3 Microbial Risk Assessment (MRA)
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Pollutant**} & \multicolumn{3}{c}{**Ingestion**} & \multicolumn{3}{c}{**Dermal Contact**} \\ \cline{2-7}  & \multicolumn{2}{c}{**HQ**} & \multicolumn{2}{c}{**CR**} & \multicolumn{2}{c}{**HQ**} & \multicolumn{2}{c}{**CR**} \\ \cline{2-7}  & **Adult** & **Child** & **Adult** & **Child** & **Adult** & **Child** & **Adult** & **Child** \\ \hline Al & \(1.18\times 10^{-7}\) & \(2.76\times 10^{-7}\) & - & - & \(2.07\times 10^{-3}\) & \(3.79\times 10^{-3}\) & - & - \\ Ba & \(4.36\times 10^{-8}\) & \(1.02\times 10^{-7}\) & - & - & \(5.33\times 10^{-5}\) & \(9.79\times 10^{-5}\) & - & - \\ Co & \(1.28\times 10^{-6}\) & \(2.98\times 10^{-6}\) & - & - & \(8.93\times 10^{-3}\) & \(1.64\times 10^{-2}\) & - & - \\ Cu & \(6.01\times 10^{-7}\) & \(1.40\times 10^{-6}\) & - & - & \(2.83\times 10^{-1}\) & \(5.19\times 10^{-1}\) & - & - \\ Fe & \(9.24\times 10^{-7}\) & \(2.16\times 10^{-6}\) & - & - & \(4.39\times 10^{-4}\) & \(8.06\times 10^{-4}\) & - & - \\ Mn & \(7.32\times 10^{-7}\) & \(1.71\times 10^{-6}\) & - & - & \(7.38\times 10^{-5}\) & \(1.35\times 10^{-4}\) & - & - \\ Mo & \(5.06\times 10^{-7}\) & \(1.18\times 10^{-6}\) & - & - & \(1.16\times 10^{-1}\) & \(2.13\times 10^{-1}\) & - & - \\ Ni & \(4.58\times 10^{-5}\) & \(1.07\times 10^{-4}\) & - & - & \(6.40\times 10^{-3}\) & \(1.18\times 10^{-2}\) & - & - \\ Pb & \(9.46\times 10^{-6}\) & \(2.21\times 10^{-5}\) & \(4.77\times 10^{-30}\) & \(2.78\times 10^{-10}\) & \(9.66\times 10^{-1}\) & \(1.77\times 10^{-6}\) & \(4.87\times 10^{-5}\) & \(2.23\times 10^{-5}\) \\ Zn & \(6.44\times 10^{-6}\) & \(1.50\times 10^{-5}\) & - & - & \(6.76\times 10^{-5}\) & \(1.24\times 10^{-4}\) & - & - \\ \hline Total & \(6.59\times 10^{-5}\) & \(1.54\times 10^{-4}\) & \(4.77\times 10^{-30}\) & \(2.78\times 10^{-10}\) & \(1.38\times 10^{0}\) & \(2.54\times 10^{0}\) & \(4.87\times 10^{-5}\) & \(2.23\times 10^{-5}\) \\ \hline Adult total HQ & & & & \(1.38\times 10^{9}\) & & & \\ \hline Child total HQ & & & & \(2.54\times 10^{9}\) & & & \\ \hline Adult total CR & & & & \(4.87\times 10^{-5}\) & & & \\ \hline Child total CR & & & & \(2.23\times 10^{-5}\) & & & \\ \hline \multicolumn{7}{c}{HQ—hazard quotient; CR—cancer risk; - not applicable to the available data.} \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Human health risk assessment values for the residents of Kraków, in reference to roof runoff exposure pathways. Grzyb and Fraczek [79], and in Poznan, detected by [PERSON] et al. [89] were at similar levels, while the air in Gliwice [80] and Warszawa [109], was clearly less microbiologically contaminated. Plate counting of microorganisms, applied during this study, allowed us to evaluate the amounts of viable forms only. Although that method has been widely used in microbial studies, it is worth noting that real amounts of microorganisms in the environmental samples are much higher, since either some of microbes are not able to grow on artificial media, or are simply dead. [PERSON] and [PERSON] [109] demonstrated that viable forms constituted only up to 0.3% of all microorganisms detected in the air. However, it is known that even dead microorganism may cause irritation of skin, eyes, or respiratory tract, owing to the presence of allergens or toxins in their cells [110], posing a serious threat to human health. Although the physical and chemical quality of the Krakow roof runoff is generally good, its microbiological condition is much more disturbing and disqualifies roof runoff from potable use, without previous treatment. Approximate results, leading to similar conclusions, were obtained by [PERSON] et al. [106].