Jose Picayo

Lead: This heavy metal, which often leaches into water from household pipes and plumbing fixtures, can, at high levels, cause neurological damage and developmental delays in children.
Arsenic: This natural poison is found in rocks and soil. It is also released into the environment through mining and coal burning; eventually it seeps into ground water. Arsenic may cause cancer, nervous-system damage, and birth defects.
Germs: Microbes, such as cryptosporidium and giardia, can get into lakes and rivers and may end up in your water. They can cause serious illnesses in the young, the elderly, and those with suppressed immune systems.
Disinfection by-products (DBPs): Most cities add chemicals, such as chlorine, to the water supply to kill germs. But when chlorine comes into contact with such things as decomposing plant materials in water, it may form trihalomethanes and haloacetic acids, which have been linked to cancer and miscarriage in lab animals.
Other contaminants: Pesticides are a widespread problem, as are industrial chemicals. Perchlorate (rocket fuel) and the fuel additive MTBE are showing up in increasing amounts in the nation’s drinking water but aren’t yet regulated by the EPA.