Toxic minerals  

Toxic minerals, such as aluminium, arsenic, asbestos, barium, chromium, fluorine and nitrates as well as cadmium, lead and mercury could all be in tap water. These are usually found in very small quantities, but pollution caused by mining and industry may lead to an increase of these minerals in the water.

Many toxic minerals are contained in water supplies, usually at high levels. Minerals can enter surface or ground water through natural sources, industrial sewage, leach age from urban or agricultural areas, water pipes walls or even from domestic sources.