# Special Issue on Heavy Metals in the Environment--Causes and Consequences
## 2 Heavy Metals in the Environment  
The papers included in this issue present a broad spectrum of studies on the contamination of the environment with heavy metals and on the determinants and effects of their increased concentrations. These studies are concerned with the content of heavy metalsin all components of the environment, i.e., the air, water, soil, and living organisms. The investigations have been conducted on land, in urban and rural areas, as well as in seas. In most cases, these studies have a practical dimension because, apart from determining specific heavy metal content, the authors have also indicated the health-related consequences of pollution, as well as ways of mitigating the negative effects. The study by [PERSON] et al. [7] demonstrates a very strong Pb, Fe, and Mn contamination of the Aries river (eastern Romania) that drains former mining areas. This takes place despite the fact that industrial activity has been discontinued in that area. The pollution necessitates a special treatment of the water before it is used, as well as appropriate management of water resources in the catchment to prevent adverse health effects. The investigations conducted indicate that the pollutants occurring in former mining areas pose a serious threat to the environment and require special attention. [PERSON] et al. [8] have investigated the geochemistry of water coming from rooftops in the city of Krakow (southern Poland). Water runoff from the city, including water from the roofs, is an important factor affecting the quality of surface water. In chemical terms, the pollution of water runoff from roofs is not considerable, even though non-carcinogenic risk values indicate the existence of health hazards. Carcinogenic risk occurs in the case of Pb. Microbiological pollution has also been found in water under study. This indicates that the quality of water runoff from the roofs should be taken into account when identifying health and environmental risk in urban areas. [PERSON] et al. [9] have studied heavy metal levels in sewage sludge, which can potentially be used as fertilizer, originating from three wastewater treatment plants located in Swietokrzyskie Province (central Poland). It is particularly important because heavy metals that leach into the soil can enter the food chain and thus pose a health risk to people consuming contaminated food. The form in which the metals occur is particularly significant, as it influences their mobility in the environment. The studies conducted have shown that, despite increased heavy metal levels in sewage sludge (Zn in particular), using them as fertilizer does not pose a high health risk. Increased heavy metal concentrations in marine organisms are a major problem in many places around the world because they can enter the human food chain. [PERSON] et al. [10] have studied heavy metal levels in water and in juvenile fish occurring at the estuary of the Valdivia river (Chile). While no pollution of marine water has been detected, very clear differences occur in heavy metal concentration depending on the fish species: it was clearly greater in puyes (_Galaxias maculatus_) than in silversides (_Odontesthes regia_). For some elements (Zn, Pb, and Cd), greater concentrations have been found in larger (older) specimens. Heavy metal levels in the bodies of the fish under study have been found to be higher than those reported in the literature so far. In the case of puyes, Pb and Cd concentrations are above the permitted limits and thus pose a health risk if the fish is consumed by people. [PERSON] and [PERSON] [11] have investigated heavy metal content in street dust collected from the streets in Lublin (eastern Poland). The dust, resulting from the interaction of air, water, soil, and direct anthropogenic delivery, is a good indicator of the quality of the environment in the city. At the same time, the resuspension of street dust can cause air pollution in areas frequented and inhabited by people.