Aluminium deposition in bone after contamination of drinking water supply

The biological behaviour and bioavailability of aluminium in man, with special reference to studies employing aluminium-26 as a tracer: review and study update

Until 1990 biokinetic studies of aluminium metabolism and biokinetics in man and other animals had been substantially inhibited by analytical and practical difficulties. Of these, the most important are the difficulties in differentiating between administered aluminium and endogenous aluminium-especially in body fluids and excreta and the problems associated with the contamination of samples with environmental aluminium. As a consequence of these it was not possible to detect small, residual body burdens of the metal following experimental administrations. Consequently, many believed aluminium to be quantitatively excreted within a short time of uptake in all, but renal-failure patients. Nevertheless, residual aluminium deposits in a number of different organs and tissues had been detected in normal subjects using a variety of techniques, including histochemical staining methods. In order to understand the origins and kinetics of such residual aluminium deposits new approaches were required. One approach taken was to employ the radioisotope (67)Ga as a surrogate, but this approach has been shown to be flawed-a consequence of the different biological behaviours of aluminium and gallium. A second arose from the availability, in about 1990, of both (26)Al-a rare and expensive isotope of aluminium-and accelerator mass spectrometry for the ultra-trace detection of this isotope. Using these techniques the basic features of aluminium biokinetics and bioavailability have been unravelled. It is now clear that some aluminium is retained in the body-most probably within the skeleton, and that some deposits in the brain. However, most aluminium that enters the blood is excreted in urine within a few days or weeks and the gastrointestinal tract provides an effective barrier to aluminium uptake. Aspects of the biokinetics and bioavailability of aluminium are described below.

Oral aluminum administration to rats wih normal renal function. 1. Impairment of erythropoiesis

Aluminum (Al) toxicity has been mainly investigated in uremic patients although healthy subjects and patients without renal insufficiency are not exempt from its potential deleterious effects. This experimental study aims to elucidate the action of different doses of Al citrate on in vivo erythropoiesis and find out whether the metal exerts a local toxic effect upon the bone marrow late erythroid progenitor cells. The groups in the first experimental series were: C1 (n=5) controls and TAl-1 (n=5) rats receiving 1 micromol Al citrate/g body weight/day by gavage. Colony-forming units-erythroid (CFU-E) development was inhibited in the TAl-1 group, but the median osmotic fragility (MOF) and hematocrit (Ht) values were similar to those of the C1 group. The groups in the second series were C2 (n=5) controls and TAl-2 (n=5) rats receiving Al citrate in drinking water (100 mmol/l). The TAl-2 group showed decreased Ht, hemoglobin concentration, MOF and red blood-cell life-span values (P<0.05), and a marked inhibition of the CFU-E development (P<0.01). Serum and bone Al concentrations were increased in both Al-treated groups (P < 0.01). There was a dose-dependent increase in bone Al levels (P < 0.01) and a dose-dependent decrease of CFU-E development (P<0.05). The CFU-E development was inversely correlated with the bone Al content (r=-0.79; P<0.05). The results demonstrate that even very low doses of Al citrate impair erythropoiesis in vivo and higher doses exert a deleterious action on both CFU-E and mature erythrocytes. This might show a local effect of Al on CFU-E caused by the bone sensitivity to the metal accumulation.

An interesting case of osteomalacia due to antacid use associated with stainable bone aluminum in a patient with normal renal function

Antacids containing aluminum and magnesium hydroxide are widely used nonprescription agents for treatment of gastritis and peptic ulcer disease. One of the side effects of these antacids is that they bind phosphate in the gut, resulting in its malabsorption. Short-term use, consistent with the directions on the manufacturer's label, is safe and effective for most patients. Heavy chronic use, even when within label, can cause serious skeletal impairment. This report concerns the case of a 39-year-old pharmacist who self-mediated for peptic ulcer disease with high doses of a potent antacid containing aluminum and magnesium hydroxide. The patient consumed over 18 kg of elemental aluminum and 15 kg of elemental magnesium over 8 years of antacid use. This treatment resulted in the clinical syndrome of severe osteomalacia due to profound phosphate depletion. Bone biopsy revealed stainable aluminum deposits along 27.6% of the total bone surface, which is a unique observation in a patient with normal renal function. Treatment included withdrawing the antacid and supplementation with phosphate, calcium, and vitamin D. She experienced marked subjective and objective improvement with this regimen. This included a striking increase in her bone mineral density occurring over the 2-year follow-up period. This case documents that long-term antacid therapy, even when used by patients with normal renal function and within the manufacturer's label recommendations, can lead to severe phosphate depletion, osteomalacia, and toxic accumulation of aluminum and magnesium. This clinical syndrome was readily treated by withdrawal of the antacid and with calcium and phosphate supplementation. Physicians recommending treatment with these compounds or learning of their patient's self-medication with them should inform the patient of the potential serious side effects these agents can cause when used chronically at maximally recommended doses.

Oral aluminum administration to rats with normal renal function. 2. Body distribution

Aluminum (Al) has no known physiological function and is not considered an essential dietary compound. Nowadays, it is recognized as an element that can produce adverse effects on biological systems. The present study determined Al partitioning in the body compartments of rats that have been orally exposed for 15 weeks. Three experimental groups were studied: Controls (C, n=19), TAl-1 (n=10) rats receiving daily doses of Al citrate (1.0 micromol/g body weight) by gavage and TAl-2 (n=13), receiving Al citrate with the drinking water (100 mmol/ l). At the end of the experimental period, the Al contents of organs and sera were determined. Results are expressed as median and range values. Comparing the TAl-2 rats with the control ones, remarkable Al accumulation could be observed in serum (4.8/2.7-16.3 vs 0.4/0.2-1.2 micromol/l, P<0.001), bone (3.33/1.78-4.85 vs 1.00/0.48-1.59 micromol/ g, P<0.001), kidney (2.33/0.96-3.15 vs 0.52/0.22-2.07 micromol/g, P<0.001), spleen (2.22/0.70-4.19 vs 0.27/ 0.11 - 0.36 micromol/g, P< 0.001) and liver (0.60/0.42-0.91 vs 0.24/0.14-0.78 micromol/g, P<0.01) while brain Al content was not significantly increased. Aluminum levels were raised in the TAl-1 group only in serum (2.8/1.3 - 10.4 micromol/ g, P < 0.001), bone (1.85/1.00-3.41 micromol/g, P < 0.001) and kidney (1.74/0.96-2.07 micromol/g, P<0.01). Bone Al concentration increased in a dose-dependent manner (TAl-2 vs TAl-1, P<0.001). The results demonstrate different tissue Al accumulation in rats chronically exposed to Al citrate, irrespective of their intact renal function.

Alzheimer's disease and the aluminium connection: A literature review

This review explores the different areas of research that, over the past 35 years, have provided grounds for linking Alzheimer's disease and aluminium. However, in spite of the growing evidence, exposure to aluminium as a risk factor is yet to be confirmed. The evidence is discussed under four headings: evidence from brain aluminium studies; evidence from aluminium uptake studies; evidence from aluminium-related neurodegenerative conditions; and evidence from chronic aluminium exposure studies: aluminium in drinking water, and by occupational exposure.

Aluminum exposure and metabolism

Aluminum (Al) is a nonessential, toxic metal to which humans are frequently exposed. Oral exposure to aluminum occurs through ingestion of aluminum-containing pharmaceuticals and to a lesser extent foods and water. Parenteral exposure to aluminum can occur via contaminated total parenteral nutrition (TPN), intravenous (i.v.) solutions, or contaminated dialysates. Inhalation exposure may be important in some occupational settings. The gut is the most effective organ in preventing tissue aluminum accumulation after oral exposure. Typically gastrointestinal absorption of aluminum from diets is < 1%. Although the mechanisms of aluminum absorption have not been elucidated, both passive and active transcellular processes and paracellular transport are believed to occur. Aluminum and calcium may share some absorptive pathways. Aluminum absorption is also affected by the speciation of aluminum and a variety of other substances, including citrate, in the gut milieu. Not all absorbed or parenterally delivered aluminum is excreted in urine. Low glomerular filtration of aluminum reflects that most aluminum in plasma is nonfiltrable because of complexation to proteins, predominantly transferrin. The importance of biliary secretion of aluminum is debatable and the mechanism(s) is poorly understood and appears to be saturable by fairly low oral doses of aluminum.

Urinary excretion of aluminium: effects of aging and diurnal variation

Aluminium (Al) is neurotoxic and a relationship between Alzheimer's disease (AD) and Al in drinking water has been suggested in epidemiological studies. In 5 patients with AD, and healthy subjects of whom 5 were aged, 6 were middle-aged and 6 were young adults, Al excretion into the urine was measured using inductively coupled plasma emission spectro-analysis. In healthy subjects, there appeared to be a relationship between age and daily Al excretion, with the highest level in the aged group, followed by the middle-aged and young adult groups. A significant positive correlation between the amount of urine and the Al excretion in the healthy subjects was also observed. Daily A1 excretion in urine in the group of patients with AD tended to be higher than that of the age matched healthy group, but further studies are needed to account for effects of drugs containing Al compounds. The Al excretion in all the groups showed some variation with the time of day, but no definite diurnal variation common to all the subjects was noted. Because of this, the use of spot urine analysis for studying A1 excretion does not seem to be reliable.

Bioavailability of labile aluminium in acidic drinking water: a study in the rat

The bioavailability of labile Al (Allab; Al3+, and monomeric hydroxo and sulfato complexes) in drinking water was studied in the rat. The hypothesis was that Allab in drinking water is more available for absorption in the gastro-intestinal tract than Al complexed in the rat feed. Male Sprague-Dawley rats were exposed to 4 mg Al/litre in acidic drinking water (pH 4-5) and 5 mg Al/kg in the feed for 10 wk. The Al intake of these rats was about twice that in a control group of rats that received Al only in the feed. Both a theoretical speciation calculation and a speciation analysis of the water in a flow injection system showed that more than 98% of the Al in the water was present as Allab. However, intake of this water did not result in increased levels of Al in the bone, liver or brain tissue of the rats. Al speciation in a simulated rat stomach indicated that Allab in drinking water is rapidly complexed by feed constituents as the water enters the acidic milieu of the stomach, resulting in a very low concentration of Allab. The concentration of dissolved Al was also low in comparison to the added amount of labile Al. The possibility of complex formation between Allab and feed components in the gastro-intestinal tract should be taken into account in further studies of the bioavailability of drinking water Al in experimental animals and in humans.

Psychological testing on schoolchildren before and after pollution of drinking water in North Cornwall

The tap water supply in Camelford, North Cornwall and environs was contaminated by aluminium and other metals in 1988. Richmond tests were routinely given before and after the pollution and here scores are compared between 39 children from schools in the contaminated area and 64 children from Cornish schools outside the polluted area. The study was retrospective and it was not possible to determine whether or how much polluted water individuals had consumed. No differences were found between groups either before or after the pollution accident nor was there any evidence for any sub-group of the polluted group which had been affected. The limits of conclusions which can be drawn from data available are discussed.

Effect of oral aluminium citrate on short-term tissue distribution of aluminium

Aluminium (Al) concentrations in the plasma, bone, lung, liver, kidney, spleen, duodenum and brain of rats were measured 2, 4 and 24 hr after a single oral dose of 0.46 mmol as Al citrate (1:5 molar ratio). Compared with control animals, very high concentrations were found at 2 hr post-administration in plasma (539 micrograms/litre) and in all tissues except the brain where Al did not change throughout the 24-hr period. The increased levels in the liver (161 ng/g) and lung (89.7 ng/g) at 2 hr were maintained until 4 hr and then decreased. At 24 hr the plasma value decreased to 24.6 micrograms/litre as compared with the peak value of 539 micrograms/litre. In a typical soft tissue such as the kidney the peak at 2 hr of 682 ng/g decreased to 241 ng/g, which was still more than 10-fold greater than the control level. Uniquely, in the case of bone Al increased throughout the period of the experiment. Our results indicate that Al in the citrate form is readily absorbed and that it appears to equilibrate rapidly between plasma and the intracellular compartments of most soft tissues but does not readily permeate the blood-brain barrier. In a group of rats previously given silicic acid in the drinking water and co-administered with the Al dose, the tissue Al distribution pattern at 4 hr post-administration was modified in comparison with the test animals not loaded with silicic acid. Al concentrations in plasma and soft tissues were significantly reduced except for the spleen, in which Al increased, and there was complete inhibition of the very high Al uptake/deposition in bone.

Camelford water poisoning accident: serial neuropsychological assessments and further observations on bone aluminium

The serial cognitive assessment of ten individuals made between 8 and 26 months after the water at Camelford in Cornwall was accidentally contaminated with aluminium sulphate, showed consistent evidence of impairment of information processing and memory. There was no obvious relationship between these impairments and measurements of anxiety and depression. Serial bone biopsies in two individuals showed that the aluminium which was present 6 and 7 months after the accident had disappeared by 19 months. In the eight individuals biopsied 12-17 months after the accident the bone showed no stainable aluminium. Thus, aluminium deposited in the bone of normal individuals can disappear within 18 months. After an accident such as that at Camelford important evidence of toxicity is likely to be missed if an investigation is delayed. The abnormal neuropsychological findings indicate cognitive impairment, but whether this was caused by an acute episode of brain damage, or other causes such as the psychological effects of stress resulting from the accident, is uncertain.

Chemical disasters

Chemical disasters are sufficiently common that plans are needed to prevent them, or to mitigate their effects should they occur. However, they are sufficiently rare that any individual is likely to have little or no experience of them. This article reviews chemical disasters which have been reported in the medical literature, and briefly discusses plans for medical involvement in the prevention and tackling of such events.

Assessment of exposure to parenteral and oral aluminum with and without citrate using a desferrioxamine test in rats

The primary purpose of this study was to determine the relative usefulness of various measures to monitor body aluminum burden in weanling rats fed various amounts of aluminum (0.39 mumol Al/g diet for 29 days, approximately 40 mumol Al/g diet with or without citrate for 29 days and approximately 100 mumol Al/g diet with citrate for 12 or 29 days) or injected intraperitoneally with graded doses of aluminum (0.01, 4.6, 11.8, 23.5 or 94 mumol Al). Twenty-four hours prior to sacrifice, all rats were injected intraperitoneally with either desferrioxamine (75 mg DFO) or buffer. All seven indices of aluminum exposure monitored (i.e. tibia, liver, kidney and serum aluminum concentrations; changes in serum aluminum concentrations in response to DFO; urinary aluminum excretion with and without DFO treatment) were highly (P < 0.001) correlated to parenteral aluminum exposure. Five of these measures (i.e. tibia, liver and serum aluminum concentrations and urinary aluminum excretion with and without DFO treatment) were also highly (P < 0.001) correlated to oral aluminum loads. Changes induced by DFO were very small. Moreover, the 'DFO stimulated' serum and urine aluminum concentrations were not more correlated to the body load of aluminum, as indicated by tibia aluminum concentrations, than baseline values. Comparisons of aluminum exposure in tibias and sera of rats exposed to parenteral and oral aluminum indicated that only 0.01-0.04% of dietary aluminum was absorbed. Ingestion of citrate had small but significant effects on aluminum retention.

Aluminium-adjuvanted vaccines transiently increase aluminium levels in murine brain tissue

Aluminium is widely used as an adjuvant in human vaccines, and children can often receive up to 3.75 mg of parenteral aluminium during the first six months of life. We show that intraperitoneal injection of aluminium adsorbed vaccines into mice causes a transient rise in brain tissue aluminium levels peaking around the second and third day after injection. This rise is not seen in the saline control group of animals or with vaccine not containing aluminium. It is likely that aluminium is transported to the brain by the iron-binding protein transferrin and enters the brain via specific transferrin receptors.

Evidence of aluminium accumulation in aluminium welders

Using atomic absorption spectrometry the aluminium concentrations in blood and urine and in two iliac bone biopsies obtained from welders with long term exposure to fumes containing aluminium were measured. The urinary excretion of two workers who had welded for 20 and 21 years varied between 107 and 351 micrograms Al/l, more than 10 times the concentration found in persons without occupational exposure. Urinary aluminium excretion remained high many years after stopping exposure. Blood and bone aluminium concentrations (4-53 micrograms Al/l and 18-29 micrograms Al/g respectively) were also raised but not to the same extent as urine excretion. It is concluded that long term exposure to aluminium by inhalation gives rise to accumulation of aluminium in the body and skeleton of health persons, and that the elimination of retained aluminium is very slow, in the order of several years.