Relationship between hair, serum and bone aluminium in hemodialyzed patients

Characterization of bone aluminum, a potential biomarker of cumulative exposure, within an occupational population from Zunyi, China

OBJECTIVES

Aluminum (Al) is a neurotoxicant; however, efforts to understand Al toxicity are limited by the lack of a quantitative biomarker of cumulative exposure. Bone Al measurements may address this need. Here, we describe and compare non-invasive bone Al measurements with fingernail Al and Al cumulative exposure indices (CEIs).

METHODS

We completed a cross-sectional study of 43 factory workers in Zunyi, China. Bone Al measurements were taken with a compact in-vivo neutron activation analysis system (IVNAA). Fingernail samples were analyzed using inductively coupled plasma mass spectrometry. CEIs, based on self-reported work history and prior literature, were calculated for the prior 5, 10, 15, 20 years and lifetime work history. Linear regressions adjusted for age and education compared fingernail Al and Al CEIs with bone Al.

RESULTS

Median (interquartile range (IQR)) Al measurements were: 15 μg/g dry bone (IQR = 28) for bone Al; 34.9 μg/g (43.3) for fingernail; and 24 (20) for lifetime CEI. In adjusted regression models, an increase in 15-year CEI was significantly associated with increased bone Al (β = 0.91, 95% confidence interval (CI): 0.16, 1.66). Associations of bone Al with 10- and 20-year CEI were approaching statistical significance (β = 0.98, 95% CI: -0.14, 2.1; β = 0.59, 95% CI: -0.01, 1.18, respectively). Other models were not statistically significant.

CONCLUSIONS

Bone Al was significantly associated with 15-year Al CEI, but not other Al CEIs or fingernail Al. Bone Al may be a useful measure of cumulative, rather than short-term, Al exposure. Additional refinement of this method is ongoing.

Longitudinal and lateral variations in the aluminum concentration of selected caprine, bovine, and human bone samples

Longitudinal and lateral variations in Al concentration in several large animal (bovine and caprine) long bones (tibia and femur) and several human clavicle bones were examined using a sensitive analytical method based on electrothermal atomization atomic absorption spectrometry with Zeeman background correction. Bone segments were carefully removed using special tools free of significant Al contamination, freeze-dried, and digested overnight at room temperature in concentrated HNO3. Bone digestates were analyzed for Al using simple aqueous calibration standards with a Ca(NO3)2 modifier. Mean bone Al concentrations were relatively low (<1 microg/g, dry weight) in bovine and caprine long bones compared to literature values for human bone samples. Longitudinal variations of Al in the animal bones examined appeared relatively uniform compared to the human clavicle bones, where, in three of five cases, Al appeared enriched at the epiphyses (joints). The Al "enrichment" was symmetrical with respect to both left and right clavicle bones. Aluminum concentrations at the mid-shaft of the clavicle bone show less variation compared to whole bone studies, but considerable scatter is evident along the bone length. The mean bone aluminum concentration in the five human subjects varied from 1 to 6 microg/g dry weight.

An evaluation of the biological significance of aluminium in plasma and hair of patients on long-term hemodialysis

In hemodialyzed patients, the risk of toxicity attributed to the body accumulation of aluminium (Al) justifies the need for monitoring Al in various human media. In this study, Al concentrations in the hair and plasma of 78 hemodialyzed patients with chronic renal failure and of 351 healthy volunteers were measured by electrothermal atomic absorption spectrometry with Zeeman effect. Plasma Al concentrations in patients were significantly higher than in the controls and positively correlated with time on dialysis. Hair Al levels were widely distributed with no significant distinction between patients and controls. On the subject of establishing correlation, the authors stress the importance of taking into account the kinetics of the elimination of minerals from hair. Even when this was done, in the patient group there was no statistical link between plasma and hair Al levels. Hair Al analysis is of no value as an indicator of body Al accumulation.