Heavy Metals heavy metals.. what are they and why are they damaging.. In small amounts our body requires metals, they can also be very damaging. Mercury: damaging to the nervous system and to brain function. Early symptoms include fatigue, insomnia, headaches, forgetfulness, impaired judgment. found in dental filling, large fish, cosmetics and medicines (especially vaccines). Cadmium:competes with zinc and ... leads to many enzyme deficiencies in the body, which leads to high free radical activity. it also interferes with kidney function.High cadmium levels have been associated to high blood pressure and cancer. fond in cigarette smoking, and fertilizers Lead: causes learning and developmental disabilities, cerebral palsy, strokes and seizures. Early signs of lead toxicity include headaches, abdominal aches, lessened memory and intelligence, and depression.found in paint and fertilizers Nickel: Lead exposure and lead body levels are higher in North America than anywhe