Mercury is present in water, soil, vegetables and seafood. Small amounts of mercury are not dangerous for health.
However, in certain concentrations over the period of time, mercury poisoning may occur.
The main sources of dangerous levels of Mercury are seafood and some machinery. Mercury poisoning from seafood occurs because of the process called biomagnification.
Mercury is known to damage the nervous system most of all. Mercury poisoning may result in shakiness (tremors), pathological shyness, nervousness, anxiety, irritability, depression, memory and concentration problems, trouble walking and vision, hearing and speech problems.