Int. J. Environ. Res. Public Health 2009, 6 3130 individual and mean Cd concentrations were several times higher than the Hg concentrations. As shown in Table 1, all the levels measured for As. Pb and Hg were below the limits recommended by the by European Regulation [26], however the Cd concentration in one kidney exceeded the maximum limit (1 ng/g) established by European Regulation [26]. On the whole, the concentration of these four analyzed toxic elements was very variable in relation to the region where samples were collected. Also, the present study has shown that toxic elements levels in kidney are comparable with those of other countries, especially within Europe [27,28]. The results of this study confirm that Hg, the toxicity of which is well documented, particularly in its organic form, is one of the main environmental contaminants. In contrast, our results showed that the Cd levels were higher than the levels of Hg in the sampled kidneys (Table 1). In only one sample was an excessive concentration of Cd found (>1.0 ng/g). Cadmium, because of its widespread distribution, movement through terrestrial food-chains, and adverse chronic effects in humans, is one of the toxic elements for which maximum acceptable concentrations have most frequently been set. Offal, especially liver and kidney from adult animals can contain relatively high cadmium levels, and concentrations in excess of 50–100 ng/g in animal tissues are considered normal [9]. The low levels of Cd contamination observed in our study can be explained by the utilization of good agricultural practices (GAP), which uses fertilizer low in Cd and restrict disposal of sewage sludge on crop land. In addition the fact that Pb was not detected in the sampled kidneys could be the results of the global reduction in the discharge of this element in environmental media. Stringent environmental legislation has led to a reduction in the discharges of these metals during the last 15 years [29]. The results from the present work indicate that there are significant regional variations in the occurrence of toxic elements in kidneys from slaughtered pigs. Regional differences in soil and cereal cadmium levels are known to be present. Differences in geographical origin of the cereals used by the three different manufacturers might thus explain the concentration differences in corresponding feedstuff formulation, as could differences in the composition of the formulas. A third, less probable explanation, is cadmium contamination during the industrial processes. The main source of human exposure to mercury is the diet. Mercury occurs in food naturally (e.g., in fish which take up mercury from marine sediments), or as a result of pollution (e.g., emissions from industrial processes, fossil fuel combustion). For non-plant feed materials, Scientific Committee on Animal Nutrition (SCAN) [30] identified fishmeal to be the most common source of mercury for farmed animals under normal farming conditions. In addition to mercury in feed materials, livestock and poultry may also be exposed to mercury in drinking water. However, water does not make a significant contribution to the exposure of livestock except in highly polluted areas. Mercury is a naturally occurring element that is also released to the environment by a variety of sources including human activities. Once released into the environment mercury undergoes a series of complex chemical and physical transformations as it cycles between atmosphere, land, and water. Humans, plants, and animals are routinely exposed to environmental mercury and accumulate it potentially resulting in a variety of health effects. Also, fishmeal normally contains lower cadmium content, but mineral feeds (mono and dicalcium phosphate) are usually structurally contaminated with Cd. Other minerals influence the absorption and tissue disposition of cadmium and vice versa. In pigs, a significant increase of cadmium accumulation