Report No DWI0781

Mar 1995

To determine the fraction of ingested aluminium taken up by the body (¦ 1) following the ingestion of aluminium-26 labelled dr1nking water by two male volunteers. To determine the kinetics of aluminium uptake following its administration in the above form.

Interventions and Measurements

The volunteers received a single oral dose of drinking water, supplied by the Sydney Water Board, Sydney, New South Wales, Australia, and containing 100 Bq ²⁶Al. The doses were given m 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 ¦ 1 (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 ¦ 1 - 0.22% was calculated for the two volunteers. Other, much lower, estimates of ¦ 1 were obtained by comparing concentrations of ²⁶AI 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 (¦ 1 range 0.01-O.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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