Heavy metals are too well-known environmental pollutants of particularly serious health hazard to human health because of the effects of their actions are not immediate, but they show up after many years. Due to their wide usage in many industrial branches they are present everywhere in the air, water and soil. Food contaminant by heavy elements is hard to avoid and it is a result of environmental contamination by dusts, industrial gases, sewage, waste and coal burning processes. The content of heavy metals in the environment is quite diverse and their harmful action depends on the type of element, the chemical form of their occurrence and the state of organism's nutrition. One of the very toxic and also very frequently used heavy metal is mercury. Exposure to mercury can cause immune, sensory, neurological, motor and behavioral dysfunctions.