Etymology

Nomenclature history

The earliest citation given in the Oxford English Dictionary for any word used as a name for this element is alumium, which British chemist and inventor Humphry Davy employed in 1808 for the metal he was trying to isolate electrolytically from the mineral alumina. The citation is from the journal Philosophical Transactions of the Royal Society of London: "Had I been so fortunate as to have obtained more certain evidences on this subject, and to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium, alumium, zirconium, and glucium."^[47][48]

Davy had settled on aluminum by the time he published his 1812 book Chemical Philosophy: "This substance appears to contain a peculiar metal, but as yet Aluminum has not been obtained in a perfectly free state, though alloys of it with other metalline substances have been procured sufficiently distinct to indicate the probable nature of alumina."^[49] But the same year, an anonymous contributor to the Quarterly Review, a British political-literary journal, in a review of Davy's book, objected to aluminum and proposed the name aluminium, "for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound."^[50]

The -ium suffix conformed to the precedent set in other newly discovered elements of the time: potassium, sodium, magnesium, calcium, and strontium (all of which Davy had isolated himself). Nevertheless, -um spellings for elements were not unknown at the time, as for example platinum, known to Europeans since the sixteenth century, molybdenum, discovered in 1778, and tantalum, discovered in 1802. The -um suffix is consistent with the universal spelling alumina for the oxide, as lanthana is the oxide of lanthanum, and magnesia, ceria, and thoria are the oxides of magnesium, cerium, and thorium respectively.

The spelling used throughout the 19th century by most U.S. chemists ended in -ium, but common usage is less clear.^[51] The -um spelling is used in the Webster's Dictionary of 1828. In his advertising handbill for his new electrolytic method of producing the metal 1892, Charles Martin Hall used the -um spelling, despite his constant use of the -ium spelling in all the patents^[44] he filed between 1886 and 1903.^[52] It has consequently been suggested that the spelling reflects an easier to pronounce word with one fewer syllable, or that the spelling on the flier was a mistake. Hall's domination of production of the metal ensured that the spelling aluminum became the standard in North America; the Webster Unabridged Dictionary of 1913, though, continued to use the -ium version.

In 1926, the American Chemical Society officially decided to use aluminum in its publications; American dictionaries typically label the spelling aluminium as a British variant.

The name "aluminum" is derived from its status as a base of alum; "alum" in turn is a Latin word which literally means "bitter salt".^[53]

Present-day spelling

Most countries use the spelling aluminium (with an i before -um). In the United States, this spelling is largely unknown, and the spelling aluminum predominates.^[54][55] The Canadian Oxford Dictionary prefers aluminum, whereas the Australian Macquarie Dictionary prefers aluminium.

The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990, but three years later recognized aluminum as an acceptable variant. Hence their periodic table includes both.^[56] IUPAC officially prefers the use of aluminium in its internal publications, although several IUPAC publications use the spelling aluminum.^[57]

Health concerns

Despite its natural abundance, aluminium has no known function in living cells and presents some toxic effects in elevated concentrations. Its toxicity can be traced to deposition in bone and the central nervous system, which is particularly increased in patients with reduced renal function. Because aluminium competes with calcium for absorption, increased amounts of dietary aluminium may contribute to the reduced skeletal mineralization (osteopenia) observed in preterm infants and infants with growth retardation. In very high doses, aluminium can cause neurotoxicity, and is associated with altered function of the blood-brain barrier.^[58] A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminium, such as deodorants or antacids. In those without allergies, aluminium is not as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts.^[59] Although the use of aluminium cookware has not been shown to lead to aluminium toxicity in general, excessive consumption of antacids containing aluminium compounds and excessive use of aluminium-containing antiperspirants provide more significant exposure levels. Studies have shown that consumption of acidic foods or liquids with aluminium significantly increases aluminium absorption,^[60] and maltol has been shown to increase the accumulation of aluminium in nervous and osseus tissue.^[61] Furthermore, aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory.^[62] These salts' estrogen-like effects have led to their classification as a metalloestrogen.

Because of its potentially toxic effects, aluminium's use in some antiperspirants, dyes (such as aluminium lake), and food additives is controversial. Although there is little evidence that normal exposure to aluminium presents a risk to healthy adults,^[63] several studies point to risks associated with increased exposure to the metal.^[64] Aluminium in food may be absorbed more than aluminium from water.^[65] Some researchers have expressed concerns that the aluminium in antiperspirants may increase the risk of breast cancer,^[66] and aluminium has controversially been implicated as a factor in Alzheimer's disease.^[67] The Camelford water pollution incident involved a number of people consuming aluminium sulphate. Investigations of the long-term health effects are still ongoing, but elevated brain aluminium concentrations have been found in post-mortem examinations of victims who have later died, and further research to determine if there is a link with cerebral amyloid angiopathy has been commissioned.^[68]

According to The Alzheimer's Society, the overwhelming medical and scientific opinion is that studies have not convincingly demonstrated a causal relationship between aluminium and Alzheimer's disease.^[69] Nevertheless, some studies, such as those on the PAQUID cohort,^[70] cite aluminium exposure as a risk factor for Alzheimer's disease. Some brain plaques have been found to contain increased levels of the metal.^[71] Research in this area has been inconclusive; aluminium accumulation may be a consequence of the disease rather than a causal agent. In any event, if there is any toxicity of aluminium, it must be via a very specific mechanism, since total human exposure to the element in the form of naturally occurring clay in soil and dust is enormously large over a lifetime.^[72][73] Scientific consensus does not yet exist about whether aluminium exposure could directly increase the risk of Alzheimer's disease.^[69]

Effect on plants

Aluminium is primary among the factors that reduce plant growth on acid soils. Although it is generally harmless to plant growth in pH-neutral soils, the concentration in acid soils of toxic Al³⁺ cations increases and disturbs root growth and function.^[74][75][76]

Most acid soils are saturated with aluminium rather than hydrogen ions. The acidity of the soil is therefore a result of hydrolysis of aluminium compounds.^[77] This concept of "corrected lime potential"^[78] to define the degree of base saturation in soils became the basis for procedures now used in soil testing laboratories to determine the "lime requirement"^[79] of soils.^[80]

Wheat's adaptation to allow aluminium tolerance is such that the aluminium induces a release of organic compounds that bind to the harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism. The first gene for aluminium tolerance has been identified in wheat. It was shown that sorghum's aluminium tolerance is controlled by a single gene, as for wheat.^[81] This is not the case in all plants.