Our domestic water can also contain too much dissolved heavy metals, such as lead and cadmium, which originates from the oxidation of plumbing materials by the chlorine, chemical water treatment using aluminium compounds and recycling of industrial effluent. Aluminium intake is linked to Alzheimer’s disease, whereas lead intake is especially dangerous to children and pregnant women because it can impair a child’s mental and physical development. Prolonged exposure to increased lead levels also can cause aggressive behaviour, hyperactivity and learning problems. In adults, increased lead levels have been linked to high blood pressure and damaged hearing. Serious lead poisoning can lead to blindness, brain damage and mental retardation.