Aluminium is the most abundant metal in the earth's crust, 8.8% by weight, exceeded in abundance only by oxygen and silicon. Aluminium does not occur naturally in the metallic state; however it is widely distributed in rocks, clay and soils in the form of gems such as ruby, sapphire and turquoise and in minerals of industrial importance such as alum, bauxite, cryolite, corundum and kaolin.
Because of the ubiquitous distribution of aluminium compounds, natural human exposure is unavoidable, and moderate amounts of the element enter the body constantly through inhalation of atmospheric dusts and ingestion of food and drink. Despite an oral intake ranging from 5 10 mg daily, little aluminium is absorbed and serum levels of 0.07-0.30 mol/L are usually found. Tissue aluminium levels are very low. No biological function for the metal has been found, moreover, life has evolved in an environment so rich in aluminium that it would be surprising if human beings could not tolerate substantial variations in exposure without ill effects. Under most circumstances this tolerance appears to hold. Industrial aluminium toxicity is rare and tissue concentrations of the metal have apparently been affected little by extensive use of aluminium products and cookware. The application of thousands of kilograms of aluminium products as antiperspirants has not caused toxicity except for occasional local irritation. Indeed, a considerable body of experimental data gathered over many years suggests the presence of formidable epithelial barriers to aluminium absorption in the lung, the gastrointestinal tract and the skin.
High levels of aluminium can accumulate in the tissues of patients with chronic renal failure2 on long term haemodialysis treatment. The increased tissue load of aluminium may be derived from:
1. Intestinal absorption following administration of aluminium hydroxide gels used to control the high plasma phosphate levels found in chronic renal failure (May also be used as an antacid). Patients have in the past ingested up to several kilograms of elemental aluminium over their dialysis 'career'
2. Water used for haemodialysis may contain aluminium which will dialyse across the dialysis membrane and lead to raised plasma aluminium and tissue aluminium levels. A single dialysis may expose the patient's blood to as much as 250 L of water (39 000 L per year)
3. The dialysis concentrate used to prepare the dialysate may contain high levels of aluminium and lead to substantial contamination of the dialysate fluid
The increased tissue content of aluminium appears to be the major factor in the aetiology of dialysis dementia and dialysis osteodystrophy. The prevention of iatrogenic aluminium poisoning involves caution in the use of aluminium containing oral phosphate binders, together with regular monitoring of:
i. the aluminium content of the dialysate
ii. the domestic tap water used to prepare the dialysate and
iii. monitoring of serum aluminium levels in patients on long term haemodialysis treatment
Lipids/Trace Metals
PAL
5 days
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