Heavy metals are dangerous because they tend to bioaccumulate. Bioaccumulation means an increase in the concentration
of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Compounds
accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.
Heavy metals can enter a water supply by industrial and consumer waste, or even from acidic rain breaking down soils and
releasing heavy metals into streams, lakes, rivers, and groundwater. Heavy metal toxicity can result in damaged or reduced
mental and central nervous function, lower energy levels, and damage to blood composition, lungs, kidneys, liver, and other
vital organs. Long-term exposure may result in slowly progressing physical, muscular, and neurological degenerative
processes that mimic Alzheimer's disease, Parkinson's disease, muscular dystrophy, and multiple sclerosis. Allergies are not
uncommon and repeated long-term contact with some metals or their compounds may even cause cancer (International
Occupational Safety and Health Centre1999).