Metalloids and heavy metals such as arsenic, cadmium, mercury or lead have demonstrated their environmental toxicities being highly harmful to humans; therefore deserve to be regulated explicitly (the phenomenon of speciation). Lead has been widely used by mankind and therefore is causing more problems and more concern around the world. Metalloid most used in the extraction of gold, silver and copper mining activities is mercury; Once you can move great distances that is emitted into the atmosphere can settle in aquatic media transformed into methyl mercury (powerful neurotoxin) ingestion of food contaminated (above all fish) represent the greatest risk of poisoning due to its biotransformation and biological magnification through the food chain. Acute mercury poisoning is characterized by disorders of intestinal and kidney function and chronic deterioration of the central nervous system; mild exposures are characterised by loss of memory, tremors, emotional instability (anxiety and irritability), insomnia and loss of appetite. To moderate exposures, there are major mental disorders and motor disturbances, as well as kidney disease. Brief exposures to high levels of mercury vapor can cause lung damage and death. Evidences abound; lead is a metal used in industrial processes, also found naturally in the Earth’s crust, where it is extracted and processed for diverse applications. Lead ingested, inhaled or absorbed through the skin is highly toxic to living things, in general.

It is toxic to the endocrine, cardiovascular, respiratory, neurological and immune systems, and gastrointestinal addition can affect the skin and kidneys. When this metal reached toxic levels causes the decrease in plant photosynthesis and the development of anemia in mammals. The lead is not biodegradable and persists on the ground, in the air, in water and in homes. It never disappears but it accumulates at sites in which is deposited and can poison to generations of children and adults, unless it is withdrawn. The concentration of 7 micrograms of lead per deciliter of blood (? g/dL) cause irreversible damage to the neurological system of infants.Lead causes anemia in children and adults, as well as kidney disease and affects fertility.