Report No DWI0689

The Bioavailability in Young Adults of Aluminium Ingested in Drinking Water

DWI0689

Mar 1995

EXECUTIVE SUMMARY

Objectives

To determine the fraction (f1) of ingested aluminium taken up by the body following the ingestion of 26Al-labelled drinking water by two male volunteers; to investigate the kinetics of aluminium uptake and clearance following its administration in this form.

Interventions and Measurements

The volunteers received a single oral dose of drinking wafer, supplied by the Sydney Water Board, Sydney, New South Wales, Australia, and confining 100 Bq 26Al. The doses were given in the morning after overnight fasting

Blood, urine and faeces samples collected from the volunteers were analysed for their 26Al contents, using either coincidence gamma-ray spectrometry or accelerator mass spectrometry (AMS). AMS measurements were made in Canberra using the Australian National University's tandem Van de Graaff accelerator. The measured levels in blood and urine were used to calculate f1 (as defined above) and those in faeces were used to confirm the administered dose of 26Al.

Main Findings

Based on the urinary output of 26Al previously given to other subjects by intravenous injection, a mean f1 = 0.22% was calculated for the two volunteers. Other, much lower, estimates of f1 were obtained by comparing concentrations of 26Al in the volunteers' blood with published levels following intravenous injection, but this approach was shown to be invalid. The results showed differences between the kinetics of uptake in the two volunteers, the subject exhibiting the higher uptake also showing a longer residence time of aluminium in the gut.

Conclusions

Less than 0.3% of the administered dose was absorbed, which it was estimated would lead to a long-term retention of less than 0.02% of the intake. These fractions are of the same order as those measured or inferred in another study where mixtures of aluminium hydroxide and/or aluminium citrate were administered (f1 range 0.01 0.5%).

If is likely that average levels of aluminium in drinking water contribute only about 1% of the daily uptake of this element.

Published estimates of bioavailability, based only on blood sampling at a single time point following ingestion, are likely to be inaccurate.

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