# Possible Health Effects of Road Dust in Winter: Studies in Poland
## 4 Conclusions  
Based on URD studies, we can conclude that both studied regions, Upper and Lower Silesia, are quite heavily polluted in winter in terms of dust pollution. Although sites in Piekary Slaskie, Upper Silesia (sites 5 and 6) can be characterised by an enormously high content of Zn, As, and Al, probably resulting from the heating type used by inhabitants (mainly coal-fired domestic stoves), the presence of active industries, abandoned waste dumps, and heavy traffic in this region makes Piekary Slaskie one of the most polluted of our studied regions, and living there definitely poses a high health risk for inhabitants. The conducted health risk studies indicate that the intake of contaminated URD is the major pathway of exposure to the metals. The overall hazard index (HI) was more than one in the case of URD-bound As (adults) and Pb (children) in the Upper Silesia region. In the Wroclaw agglomeration, the score was low, which suggests a higher harmfulness of the URD for human health in the Upper Silesia region. Excess cancer risk (ECR) values for all studied URD-bound elements were not within safe limits, i.e., under the range limit of \(10^{-6}\) in Piekary Slaskie, Upper Silesia (site 6). Exceeded values of ECR for all elements were also recorded at two traffic-related sites in Wroclaw (site 3). These findings suggest that URD poses a serious carcinogenic risk in both regions, although the values from the Katowice agglomeration were much higher. When we compare our results with summer studies, we can conclude that URD in winter produces much higher carcinogenic risk to inhabitants of both regions, but this risk is more severe for the Upper Silesia agglomeration. A comprehensive assessment of both regions using the PI, PLI, EF, and Igeo pollution indices was also made. According to the pollution index (PI), Zn, Pb, As, and Cd were the primary pollutants in Upper Silesia, where their scores were a few times higher than those in Lower Silesia. The pollution index (PLI) shows that all sites in the Upper Silesia region are more severely polluted than the second studied region. Based on the PLI, we can note that the level of pollution in Upper Silesia is higher in winter, which is probably a result of domestic heating. The results of the Enrichment Factor (EF) of URD samples show that URD-bound Zn, As, Pb, and Cd in Piekary Slaskie (site 6, Upper Silesia) have extremely strong enrichment. On the other hand, URD from Lower Silesia was extremely highly enriched with Ni, Cu, Zn, As, Cr, Co, Pb, and Cd (site 1). The highest value of the EF index was obtained for URD from site 6 for As in Upper Silesia and for Ni, URD from site 1 in Lower Silesia. The average values of Igeo for the Upper Silesia region show that Zn, Pb, Cd, and As are the dominant pollutants, while in the Lower Silesia region, these are Zn, Cu, and Ni, although their values are a few times lower for the Wroclaw agglomeration. The levels of metal accumulation according to Igeo were similar for summer studies, suggesting their origin from vehicle traffic, domestic emissions, and industry or waste. To sum up, our studies show that the level of URD-bound elements is higher in Upper Silesia than in Lower Silesia in winter, which is a result of domestic heating and industrial activity in this region. Although our studies were restricted to two biggest agglomerations in Poland, the results will be useful for researchers to bridge the gap on the pollution of elements in URD from Poland, where there is a lack of such data. Finally, our studies on winter dust pollution will not only help to understand the sources of URD and control road dust emissions to reduce them in the future, but they will contribute to knowledge of possible health risks and allow for the prevention of related diseases. Furthermore, large-scale studies including various representative areas with different characteristics are recommended, as a future study, to better understand the pollution levels and emission sources of elements in URD and possible health risks to humans.