The element aluminium (atomic weight 26.98) is a silver white metal (density 2.7 g/mL). In its inorganic compound it presents only two oxidation states: 0, +3. Aluminium is the most abundant metal in the Earth’s crust, and the third most abundant element, after oxygen and silicon. Because of its extremely low redox-potential potential in nature, it is found combined in over 270 different minerals as oxides or silicates. Aluminium is remarkable for low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are very important in transportation and building. Aluminium compounds are widely used in the paper industry, in the dye production, in the textile industry, in processed food, and as a component of many cosmetic and pharmaceutical preparations. Soluble aluminium salts have demonstrated toxic effects in elevated concentrations. Its toxicity can be traced to deposition in bone and the central nervous system. Because aluminium competes with calcium for absorption, increased amounts of dietary aluminium may contribute to osteopenia (reduced skeletal mineralization). In very high doses, aluminium can cause neurotoxicity. In a smaller amount it can give in susceptible people contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion.

Owing to limitations in the animal data as a model for humans and the uncertainty surrounding the human data, a health-based WHO guideline value cannot be derived; however, practicable levels based on optimization of the coagulation process in drinking — water plants using aluminium-based coagulants are derived: 0.1 mg/L or less in large water treatment facilities, and 0.2 mg/L or less in small facilities (World Health Organization [WHO], 2008).