Bioavailability of Aluminium from Drinking Water: Co-exposure with Foods and Beverages

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Report No UWRAA 83

October 1994

SYNOPSIS

Alum (aluminium sulphate) is used in the clarification process of raw water for drinking. A recent study using Sydney drinking water has shown that after alum treatment it contained a higher proportion of soluble to insoluble aluminium species. Soluble forms of aluminium are bioavailable and toxic. They are readily absorbed from the digestive tract into the bloodstream and taken up by bone, brain and other soft tissues.

At high blood levels, aluminium causes acute dementia (dialysis dementia) in some renal failure patients. Epidemiological studies have linked aluminium content in drinking water to the incidence of Alzheimer’s disease, a dementia which usually develops over a longer time course.

The main information known about aluminium bioavailability is that citric acid from lemon juice combines with aqueous aluminium to form aluminium citrate. This is much more readily absorbed than aqueous aluminium alone. The present research studied whether other nutrients affect aluminium bioavailability from drinking water. Laboratory rats were used to establish a “relative aluminium bioavailability” database for each test diet. Changes in serum and urinary aluminium concentrations were measured as an index of aluminium absorption/bioavailability.

This research showed that diet is a prominent determinant of aluminium bioavailability from drinking water. Orange juice, coffee and wine significantly increase the amount of aluminium absorbed from water. Tea, beer, butter, and apple have no effect while beef and Vita Wheat biscuits tend to decrease aluminium absorption. For each test diet a subpopulation of rats had higher aluminium bioavailability than others and were more at risk. This finding is consistent with previous research on humans (Taylor et al., 1992; Harrington et al., 1994).

From this study and other available data, it becomes clear that aluminium is absorbed through the intestine from alum-treated drinking water. However, almost all the known facts relate to rats. Further research is urgently required to ascertain if absorption occurs to the same degree in humans. If this proves to be the case, then the small daily amount of aluminium that gains access to the body must be critically analysed to find if it produces accumulated damage to brain tissues, particularly in the elderly.

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