barium and aluminium are two elements that often appear in the same compounds and alloys. They are both soft silvery alkaline earth metals. Both are toxic in their elemental forms and also as compounds, such as barium carbonate (BaCO3) and barium nitrate (Ba(NO3)2). Barium is used to make rat poison and in fireworks to produce a green color. Its insoluble compound, barium sulfate (BaSO4), is given to patients with digestive problems to produce X-ray images of their intestines.
Aluminum (Al) is the most abundant of the metallic elements. It is found in many different minerals, including bauxite (Al2O3) and witherite (BaSO4). The alloys of aluminium have many uses, such as windows, car body parts, beer kegs and aeroplane wings. Its thermal expansion values are lower than those of copper and steel, which makes it ideal for use in containers, foils, and kitchen utensils.
A number of natural and man-made processes can lead to aluminium and barium entering the environment. For example, it is a by-product of mining, metal production and combustion of fossil fuels. It can also end up in waterways as dust particles that are carried by air and wind. The concentration of aluminium in water decreases with increasing depth, but it can still be found in waters that have very low pH values, where its solubility is greatly reduced. It is also found in the oceanic surface layers and in groundwater. The presence of high levels of aluminium and barium in infant formula may pose health risks to young children, as was shown in an investigation of the amount of these contaminants in powdered milk and non-dairy baby foods available in Lebanon.