# Heavy Metals in Urban Street Dust: Health Risk Assessment (Lublin City, E Poland)
## 4 Discussion  
Although for some heavy metals in street dust, the concentrations found in 2013 and 2018 were several times above the level of the geochemical background, the risk of non-cancer health effects was very low. The HI values for maximum and average values were usually around 0.01 (Table 8). In the case of adults, HI reached the highest values for Pb (2013), 4.8 \(\times\)\(10^{-2}\); Cr (2018), 3.4 \(\times\)\(10^{-2}\); and Cd (2013), 2.8 \(\times\)\(10^{-2}\). The situation was different in the case of CR where the greatest hazard to adults in 2013/2018, respectively, was represented by Cd (2.6 \(\times\)\(10^{-5}\)/8.5 \(\times\)\(10^{-6}\)) and Cr (2.4 \(\times\)\(10^{-5}\)/4.2 \(\times\)\(10^{-5}\)). The hazard associated with both elements was greater in 2013. The same elements posed a hazard to children, but the CR values for children were 10 or 100 times higher than for adults (2013/2018)--Cd 2.8 \(\times\)\(10^{-4}\)/1.6 \(\times\)\(10^{-4}\) and Cr (3.8 \(\times\)\(10^{-4}\)/5.4 \(\times\)\(10^{-4}\)). An additional risk associated with Ni occurred (2013/2018)--4.4 \(\times\)\(10^{-4}\)/1.3 \(\times\)\(10^{-4}\). Among carcinogenic elements, only Pb concentrations did not pose a health risk (Table 9). Figure 4: Spatial distribution of the CR index (for adults) within Lublin in 2013 and 2018. [PERSON] et al. (2019) [33] found that concentrations of heavy metals (except Cd) in street dust in Lublin were distinctly lower compared to other cities in Europe. There was a decrease in the level of contamination of street dust with heavy metals, also observed by other researchers [44; 45; 46], with the exception of Cr whose content increased slightly. The tendency for the contamination to increase occurred in other cities even though this is a sporadic phenomenon in Europe. A direct comparison of the health threat determined in this study with the results of studies conducted in other cities is difficult due to differences in the methods used to assess the concentration of metals, the size of the fraction in which the concentration was determined, or the rules adopted for the calculation of indices (exposure duration, body weight, ways of exposure to pollution, etc.). Therefore, the intensity of the threat was compared with two cities in Poland where such studies had been carried out previously. In the case of HI, the determined risk is similarly low as for Wroclaw and Krakow [29], but it should be emphasized that these two cities are definitely larger (Table 8). A comparison of CR indices for these cities with the data obtained for Lublin indicates a clearly higher risk in the latter city (Table 9). This is related to the fact that only inhalation was taken into account by [PERSON] et al. (2020) [29] as a route by which heavy metals enter the human body. On the other hand, studies conducted by [PERSON] and [PERSON] (2020) [44] took into account all three routes (inhalation, skin contact, and ingestion) and indicated that the total non-carcinogenic risk indices (HI \(>\) 1) and total carcinogenic risk indices (1.6-1.7 \(\times\) 10\({}^{-4}\)) were exceeded for both adults and children. Previous studies indicated that anthropogenic supply is the main source of elements such as Cd, Cu and Zn [30]. No influence of road traffic intensity in Lublin on the level of the local distribution of pollutants and related health threat was found. The highest spatial variation of indicators occurred in 2013 and concerned elements such as Cr, Cu and Zn. The lack of correlation between traffic intensity and the size of the health threat may result from the supply of combustion products coming from sources other than traffic to street dust [1; 12]. In the case of Lublin, the combustion of coal in private houses can be the source of pollution. The lack of links between the volume of road traffic and the level of pollution has been reported by other authors [47; 48].