Excretion and retention of low or moderate levels of aluminium by human subjects

Aluminum in vaccines: Does it create a safety problem?

For almost a century, aluminum (Al) in the form of Al oxyhydroxide (a crystalline compound), Al hydroxyphosphate (an amorphous Al phosphate hydroxide), Al phosphate, and Al potassium sulfate has been used to improve the immunogenicity of vaccines. Al is currently included in vaccines against tetanus, hepatitis A, hepatitis B, human papillomavirus, Haemophilus influenzae type b, and infections due to Streptococcus pneumoniae and Neisseria meningitidis. Official health authorities consider the inclusion of Al in most of the presently recommended vaccines to be extremely effective and sufficiently safe. However, the inclusion of Al salts in vaccines has been debated for several years because of studies that seem to indicate that chronic Al exposure through vaccine administration can interfere with cellular and metabolic processes leading to severe neurologic diseases. Children, who in their first years of life receive several vaccine doses over a reduced period of time, would be most susceptible to any risk that might be associated with vaccines or vaccine components. The main aim of this paper was to discuss the data presently available regarding Al neurotoxicity and the risk for children receiving vaccines or other pharmaceutical preparations containing Al. Analysis of the literature showed that no apparent reason exists to support the elimination of Al from vaccines for fear of neurotoxicity. The only problem that deserves attention is the suggested relationship between Al oxyhydroxide-containing vaccines and macrophagic myofaciitis or myalgic encephalomyelitis/chronic fatigue syndrome. Currently, definitive conclusions cannot be drawn on these risks and further studies must be conducted. Until then, Al remains the best solution to improve vaccine efficacy.

Protective effects of banana pectin against aluminum-induced cognitive impairment and aluminum accumulation in mice

To investigate the effect of pectin on absorption and bio-toxicity of aluminum, pectin extract (100 mg kg^-1 d^-1) from banana pulp was orally administrated to aluminum exposed mice (35 mg kg^-1 d^-1) for 6 weeks. Our result showed that body weight gain of the mice treated with aluminum plus banana pectin was 32.5% higher than that of mice exposed to aluminum alone after 6 weeks of the administration. In both the step-down inhibitory avoidance task and Morris water maze test, memory retention of aluminum-exposed mice was significantly improved by the pectin administration. Treatment with banana pectin effectively prevented absorption of aluminum from the gastrointestinal tract, total aluminum excretion of mice treated with banana pectin plus aluminum was 9.3% higher than that of mice exposed to aluminum alone on the 12th day. Aluminum level in serum, cerebrum, or cerebellum of mice treated with aluminum plus banana pectin was 30.8%, 17.5%, or 17.9% lower than that of mice exposed to aluminum alone on the 42nd day, respectively. In conclusion, banana pectin extract can effectively reduce aluminum toxicity in mice.

Safety Assessment of Alumina and Aluminum Hydroxide as Used in Cosmetics

This is a safety assessment of alumina and aluminum hydroxide as used in cosmetics. Alumina functions as an abrasive, absorbent, anticaking agent, bulking agent, and opacifying agent. Aluminum hydroxide functions as a buffering agent, corrosion inhibitor, and pH adjuster. The Food and Drug Administration (FDA) evaluated the safe use of alumina in several medical devices and aluminum hydroxide in over-the-counter drugs, which included a review of human and animal safety data. The Cosmetic Ingredient Review (CIR) Expert Panel considered the FDA evaluations as part of the basis for determining the safety of these ingredients as used in cosmetics. Alumina used in cosmetics is essentially the same as that used in medical devices. This safety assessment does not include metallic or elemental aluminum as a cosmetic ingredient. The CIR Expert Panel concluded that alumina and aluminum hydroxide are safe in the present practices of use and concentration described in this safety assessment.

In Vitro Digestibility of Aluminum from Hibiscus sabdariffa Hot Watery Infusion and Its Concentration in Urine of Healthy Individuals

Increased ingestion of aluminum (Al) can lead to its accumulation in the human body, especially in people with kidney problems. Al is also associated with several nervous diseases and its negative influence on embryo development during pregnancy has been proven in animal models. Hibiscus sabdariffa L. petals are widely used alone or in fruit tea formulas, which are recommended for drinking during pregnancy instead of tea. Its petals can contain similar and even higher amounts of Al as tea, which is a known Al accumulator. Our research investigated whether the regular intake of H. sabdariffa infusion leads to increased burden of Al. Sixteen days of ingestion of H. sabdariffa infusion (c _Al = 0.5 mg.L^-1) led to increased but unbalanced levels (15-86 μg L^-1) of Al in urine compared to a period when the infusion was not ingested. The highest amounts of Al excreted were observed every third day during the ingestion. Mild health problems, such as nausea and dizziness (which could be related to plant properties) were reported by more sensitive volunteers.Our results suggest that the tea infusion from H. sabdariffa petals increases body burden of Al and, therefore, sensitive individuals as pregnant women and people with kidney problems should be cautious with excessive consumption of hibiscus infusion or fruit teas containing this plant. However, further study including more individuals is needed to fully confirm our preliminary results.

Aluminum Homeostasis in Man

Aluminum is the most prevalent metal found in nature and represents the third most abundant element of the earth's crust. In light of man's wide exposure to aluminum compounds, a review of the literature was undertaken to determine the extent of the available literature concerning the absorption, distribution, excretion, and metabolism of aluminum in man. In relative terms, the gastrointestinal tract is the major portal of entry for aluminum. The lungs play only a minor role, and there is no evidence to suggest that the dermal absorption of aluminum occurs. The gastrointestinal tract is only very slightly permeable to aluminum and provides a relatively effective barrier to its absorption. In the blood, aluminum is primarily bound to serum proteins (80%); however, a sufficient concentration of dialyziable or “free” (20%) aluminum exists to provide for its distribution. Aluminum can be found in every tissue and a normal body content of aluminum for reference man can now be calculated at 0.295 g. Present data suggest that bone may offer a major site of aluminum deposition. Urine provides at least one mechanism of aluminum excretion. However, aluminum's low renal clearance rate (2 ml/min) clearly suggests that other more efficient mechanisms for excretion exist. In fact, preliminary data indicate that bile may play some as yet undefined role in the removal process. The lack of a biologically convenient radiolabeled form of aluminum has severely handicapped the elucidation of aluminum metabolism. The chemical form of aluminum in blood, urine, or the tissues remains unknown. The liver is believed to play some role in aluminum metabolism, but no direct proof of this is available at present.

Aluminium in allergen-specific subcutaneous immunotherapy--a German perspective

We are living in an "aluminium age" with increasing bioavailability of the metal for approximately 125 years, contributing significantly to the aluminium body burden of humans. Over the course of life, aluminium accumulates and is stored predominantly in the lungs, bones, liver, kidneys and brain. The toxicity of aluminium in humans is briefly summarised, highlighting links and possible causal relationships between a high aluminium body burden and a number of neurological disorders and disease states. Aluminium salts have been used as depot-adjuvants successfully in essential prophylactic vaccinations for almost 100 years, with a convincing positive benefit-risk assessment which remains unchanged. However, allergen-specific immunotherapy commonly consists of administering a long-course programme of subcutaneous injections using preparations of relevant allergens. Regulatory authorities currently set aluminium limits for vaccines per dose, rather than per treatment course. Unlike prophylactic vaccinations, numerous injections with higher proportions of aluminium-adjuvant per injection are applied in subcutaneous immunotherapy (SCIT) and will significantly contribute to a higher cumulative life dose of aluminium. While the human body may cope robustly with a daily aluminium overload from the environment, regulatory cumulative threshold values in immunotherapy need further addressing. Based on the current literature, predisposing an individual to an unusually high level of aluminium, such as through subcutaneous immunotherapy, has the potential to form focal accumulations in the body with the propensity to exert forms of toxicity. Particularly in relation to longer-term health effects, the safety of aluminium adjuvants in immunotherapy remains unchallenged by health authorities - evoking the need for more consideration, guidance, and transparency on what is known and not known about its safety in long-course therapy and what measures can be taken to prevent or minimise its risks. The possibility of providing an effective means of measuring aluminium accumulation in patients undergoing long-term SCIT treatment as well as reducing their aluminium body burden is discussed.

Human exposure to aluminium

Human activities have circumvented the efficient geochemical cycling of aluminium within the lithosphere and therewith opened a door, which was previously only ajar, onto the biotic cycle to instigate and promote the accumulation of aluminium in biota and especially humans. Neither these relatively recent activities nor the entry of aluminium into the living cycle are showing any signs of abating and it is thus now imperative that we understand as fully as possible how humans are exposed to aluminium and the future consequences of a burgeoning exposure and body burden. The aluminium age is upon us and there is now an urgent need to understand how to live safely and effectively with aluminium.

Accumulation and toxicity of aluminium-contaminated food in the freshwater crayfish, Pacifastacus leniusculus

The accumulation and toxicity of aluminium in freshwater organisms have primarily been examined following aqueous exposure. This study investigated the uptake, excretion and toxicity of aluminium when presented as aluminium-contaminated food. Adult Pacifastacus leniusculus were fed control (3 μg aluminium/g) or aluminium-spiked pellets (420 μg aluminium/g) over 28 days. Half the crayfish in each group were then killed and the remainder fed control pellets for a further 10 days (clearance period). Concentrations of aluminium plus the essential metals calcium, copper, potassium and sodium were measured in the gill, hepatopancreas, flexor muscle, antennal gland (kidney) and haemolymph. Histopathological analysis of tissue damage and sub-cellular distribution of aluminium were examined in the hepatopancreas. Haemocyte number and protein concentration in the haemolymph were analysed as indicators of toxicity. The hepatopancreas of aluminium-fed crayfish contained significantly more aluminium than controls on days 28 and 38, and this amount was positively correlated with the amount ingested. More than 50% of the aluminium in the hepatopancreas of aluminium-fed crayfish was located in sub-cellular fractions thought to be involved in metal detoxification. Aluminium concentrations were also high in the antennal glands of aluminium-fed crayfish suggesting that some of the aluminium lost from the hepatopancreas is excreted. Aluminium exposure via contaminated food caused inflammation in the hepatopancreas but did not affect the number of circulating haemocytes, haemolymph ion concentrations or protein levels. In conclusion, crayfish accumulate, store and excrete aluminium from contaminated food with only localised toxicity.

APP expression, distribution and accumulation are altered by aluminum in a rodent model for Alzheimer's disease

Up-regulated expression of amyloid precursor protein (APP) occurs early in the cascade of events that leads to amyloid plaque formation in the human brain. APP gene up-regulation, mediated by activated NF-kappaB, is a response to stress from nM concentrations of aluminum ions, aluminum-disregulated iron ions, reactive-oxygen species, cytokines, and physical trauma. We examined in vivo effects of aluminum on APP in aged rats, obtained from previously-reported longitudinal studies, that chronically ingested aluminum in amounts equivalent to total dietary aluminum levels that Americans routinely ingest. These rats exhibited two outcomes: one group remained cognitively-intact, scoring as well on a memory-discrimination task in old age as in middle age. The other developed cognitive deterioration, obtaining significantly lower mean performance scores in old age than in middle age and exhibiting abnormal behaviors associated with dementia. We compared the expression, distribution and accumulation of APP in hippocampal and cortical tissue of these two rat groups. Compared to results from cognitively-intact rats, hippocampal and cortical tissue from the cognitively-deteriorated rats showed elevated APP gene expression, significantly more dense APP deposits in cytoplasm of neural cells, and APP-immunoreactive neurites that were swollen and varicose. This study shows aluminum routinely derived from chronic oral ingestion, that gradually accumulates in brain regions important for memory-processing, is sufficient to increase APP levels in neural cells of those regions. Aluminum may thus launch the cascade that results in the formation of amyloid plaques in human brain.

Aluminum bioavailability from basic sodium aluminum phosphate, an approved food additive emulsifying agent, incorporated in cheese

Oral aluminum (Al) bioavailability from drinking water has been previously estimated, but there is little information on Al bioavailability from foods. It was suggested that oral Al bioavailability from drinking water is much greater than from foods. The objective was to further test this hypothesis. Oral Al bioavailability was determined in the rat from basic [26Al]-sodium aluminum phosphate (basic SALP) in a process cheese. Consumption of approximately 1g cheese containing 1.5% or 3% basic SALP resulted in oral Al bioavailability (F) of approximately 0.1% and 0.3%, respectively, and time to maximum serum 26Al concentration (Tmax) of 8-9h. These Al bioavailability results were intermediate to previously reported results from drinking water (F approximately 0.3%) and acidic-SALP incorporated into a biscuit (F approximately 0.1%), using the same methods. Considering the similar oral bioavailability of Al from food vs. water, and their contribution to the typical human's daily Al intake ( approximately 95% and 1.5%, respectively), these results suggest food contributes much more Al to systemic circulation, and potential Al body burden, than does drinking water. These results do not support the hypothesis that drinking water provides a disproportionate contribution to total Al absorbed from the gastrointestinal tract.

Aluminum load in ICU patients during stress ulcer prophylaxis

BACKGROUND

Accumulating evidence has linked high aluminum (Al) levels with toxicity and disease. Our objective was to evaluate the Al exposure of ICU patients receiving stress ulcer prophylaxis with sucralfate and ranitidine.

METHODS

Within a large prospective, randomized study, a subgroup of 30 critically ill, renally intact patients on prolonged mechanical ventilation who were being treated in intensive care units (ICU) of a university hospital were allocated to two prophylaxis subgroups: enteral sucralfate, 1 g six times daily by gastric tube (n=15), or intravenous ranitidine, 200 mg daily by 24-h continuous intravenous infusion (n=15). The Al content of large and small-volume parenterals was measured and Al intake calculated for each patient and day. Aluminum levels in serum and 24-h urine were monitored every 2 days during the 16-day observation period (days 0-15).

RESULTS

Mean daily parenteral Al exposure ranged from 101.3 to 158.7 mug/day for sucralfate and ranitidine patients, respectively. In both groups, Al serum levels increased from baseline on days 1-13 and on days 3-7 in the sucralfate and ranitidine groups, respectively. From days 3-13, Al serum levels were significantly higher with sucralfate than with ranitidine (P<0.05). On days 7-13, 24-h urinary Al excretion was also significantly higher in the sucralfate than in the ranitidine group (P<0.05).

CONCLUSION

In ICU patients, only approximately 50% of parenterally administered Al is eliminated renally. Sucralfate additionally increases patients exposure to Al. In ICU patients, the mean absorption of enteral Al from sucralfate is only 0.019%.

Soil ingestion in children and adults in the same family

Ingestion of soil may be a potentially important pathway of exposure to environmental pollutants. Although several studies have estimated soil ingestion in children, data on ingestion in adults are sparse. The purposes of this study were to estimate soil ingestion in children aged 3 to 8 years and their parents, identify factors associated with increased ingestion, and compare ingestion rates within the same family. Food/liquid, excreta, and soil/dust samples were collected for the mother, father, and participant child for 11 consecutive days in 19 families. Soil ingestion was estimated using a mass balance approach. Soil ingestion levels in children were similar to those reported previously, whereas adult estimates were somewhat higher than previous estimates. Children's eating of dirt and parents' occupational contact with soil were associated with increased ingestion. Within families, soil ingestion levels in children and adults were not correlated, although this analysis was based on fewer than 19 participant families. Children's mean soil ingestion rates ranged from 37 to 207 mg/day depending on the tracer, with the highest values based on titanium as a tracer. Adult mean soil ingestion rates ranged from 23 to 625 mg/day depending on the tracer, with the highest value based on titanium as a tracer. Soil ingestion rate estimates were more variable in adults than in children.

Aluminium content of some foods and food products in the USA, with aluminium food additives

The primary objective was to determine the aluminium (Al) content of selected foods and food products in the USA which contain Al as an approved food additive. Intake of Al from the labeled serving size of each food product was calculated. The samples were acid or base digested and analysed for Al using electrothermal atomic absorption spectrometry. Quality control (QC) samples, with matrices matching the samples, were generated and used to verify the Al determinations. Food product Al content ranged from <1-27,000 mg kg(-1). Cheese in a serving of frozen pizzas had up to 14 mg of Al, from basic sodium aluminium phosphate; whereas the same amount of cheese in a ready-to-eat restaurant pizza provided 0.03-0.09 mg. Many single serving packets of non-dairy creamer had approximately 50-600 mg Al kg(-1) as sodium aluminosilicate, providing up to 1.5 mg Al per serving. Many single serving packets of salt also had sodium aluminosilicate as an additive, but the Al content was less than in single-serving non-dairy creamer packets. Acidic sodium aluminium phosphate was present in many food products, pancakes and waffles. Baking powder, some pancake/waffle mixes and frozen products, and ready-to-eat pancakes provided the most Al of the foods tested; up to 180 mg/serving. Many products provide a significant amount of Al compared to the typical intake of 3-12 mg/day reported from dietary Al studies conducted in many countries.

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.

Radio frequency chaff: the effects of its use in training on the environment

Chaff is a radiofrequency countermeasure released by military aircraft, ships, and vehicles to confuse enemy radar. Chaff consists of aluminum-coated glass fibers ranging in lengths from 0.8 to 0.75 cm and is released in packets of 0.5 to 100 million fibers. The Department of Defense has determined that use of chaff in training is required for maintaining proficiency in the use of this countermeasure. At least 500 tons of chaff is released annually during training within selected military operating areas in the United States. Concerns have been raised about impact on the environment and its potential toxicity to humans, livestock, and wildlife. Many of these concerns have been addressed or are being researched by the Department of Defense and other agencies, but much of the data are unpublished. Herein, the authors summarize the issues and review scientific data for the impact of chaff use on humans, animals, and the environment.

Sevelamer, a phosphate-binding polymer, is a non-absorbed compound

OBJECTIVE

To examine the absorption, distribution and excretion of sevelamer hydrochloride in rats and humans.

PARTICIPANTS

Twelve male Sprague-Dawley rats were used in the animal study, and twenty human volunteers participated in the clinical trial.

METHODS

In the animal study, six rats received a single oral dose of [(3)H]sevelamer and six rats were pretreated with unlabelled sevelamer in the diet for 28 days followed by a single dose of [(3)H]sevelamer on day 29. Total urine and faeces were collected at intervals up to 72 hours post dose, and tissues were obtained at the time of sacrifice. In the clinical trial, subjects received a single oral dose of [(14)C]sevelamer following 28 days of pretreatment with unlabelled sevelamer. Blood, urine and faeces samples were collected at intervals up to 96 hours.

RESULTS

In the rat study, no significant urinary excretion of radioactivity was observed. The average recovery of radioactivity in the faeces was 98% in the single-dose group and greater than 100% in the group pretreated with unlabelled sevelamer for 28 days. A total of less than 0.1% of the dose was found in the tissues. In the human study, no detectable amount of (14)C was found in the blood of any subject at any time. The majority of subjects had no detectable amounts of (14)C recovered in the urine. In subjects where (14)C was recovered in the urine, less than 0.02% was detected, a level equivalent to the free (14)C detected in the [(14)C]sevelamer preparation. On average, greater than 99% of the administered dose was recovered in the faeces of the subjects.

CONCLUSION

These studies demonstrate that sevelamer is a non-absorbed compound.

Aluminum toxicokinetics regarding infant diet and vaccinations

Some vaccines contain aluminum adjuvants to enhance the immunological response, and it has been postulated that this aluminum could contribute to adverse health effects, especially in children who receive a vaccination series starting at birth. The pharmacokinetic properties and end-point toxicities of aluminum are presented. In assessing the relevance of dietary and medical aluminum exposure to public health, we estimated infant body burdens during the first year of life for breast milk and formula diets and for a standard vaccination schedule. We then compared those body burdens with that expected for intake at a level considered safe for intermediate-duration exposure. The methodology blends intake values and uptake fractions with an aluminum retention function derived from a human injection study using radioactive 26Al. The calculated body burden of aluminum from vaccinations exceeds that from dietary sources, however, it is below the minimal risk level equivalent curve after the brief period following injection.

Safety evaluation of dietary aluminum

Aluminum is a nonessential metal to which humans are frequently exposed. Aluminum in the food supply comes from natural sources, water used in food preparation, food ingredients, and utensils used during food preparations. The amount of aluminum in the diet is small, compared with the amount of aluminum in antacids and some buffered analgesics. The healthy human body has effective barriers (skin, lungs, gastrointestinal tract) to reduce the systemic absorption of aluminum ingested from water, foods, drugs, and air. The small amount of aluminum (<1%) that is systemically absorbed is excreted principally in the urine and, to a lesser extent, in the feces. No reports of dietary aluminum toxicity to healthy individuals exist in the literature. Aluminum can be neurotoxic, when injected directly into the brains of animals and when accidentally introduced into human brains (by dialysis or shrapnel). A study from Canada reports cognitive and other neurological deficits among groups of workers occupationally exposed to dust containing high levels of aluminum. While the precise pathogenic role of aluminum in Alzheimer's disease (AD) remains to be defined, present data do not support a causative role for aluminum in AD. High intake of aluminum from antacid for gastrointestinal ailments has not been reported to cause any adverse effects and has not been correlated with neurotoxicity or AD. Foods and food ingredients are generally the major dietary sources of aluminum in the United States. Cooking in aluminum utensils often results in statistically significant, but relatively small, increases in aluminum content of food. Common aluminum-containing food ingredients are used mainly as preservatives, coloring agents, leavening agents, anticaking agents, etc. Safety evaluation and approval of these ingredients by the Food and Drug Administration indicate that these aluminum-containing compounds are safe for use in foods.

Interaction of aluminum with exogenous and endogenous iron in the organism of rats

The aim of these experiments was to find changes in free erythrocyte protoporphyrins (FEP) and in the concentration of endogenous iron in the blood, erythrocytes, serum, liver, kidneys, and spleen of rats, as well as in the dynamics of aluminum concentrations in the serum of rats after oral application of aluminum chloride (AlCl(3)) separately or with ferrum chloride (FeCl(2)), depending on the time and doses administered. The experiments were carried out on female Wistar rats which received (p.o.) 100 mg Al/kg separately or with iron (4 mg Fe/kg) daily for 35 days. The effects of aluminum administration were noticed after the second week. The experiments demonstrated that the increase in the level of free erythrocyte protoporphyrins in the blood is the most sensitive indicator of exposure to AlCl(3). A decrease in iron concentration in erythrocytes, blood, and spleen was also noticed. The response and the sequence of the investigated effects were recorded according to aluminum and iron concentration in the serum. Joint administration of iron and aluminum decreases concentration of aluminum in serum and prevents changes in the investigated indicators in rats exposed to aluminum chloride.

The application of in vitro data in the derivation of the acceptable daily intake of food additives

The acceptable daily intake (ADI) for food additives is commonly derived from the NOAEL (no-observed-adverse-effect level) in long-term animal in vivo studies. To derive an ADI a safety or uncertainty factor (commonly 100) is applied to the NOAEL in the most sensitive test species. The 100-fold safety factor is considered to be the product of both species and inter-individual differences in toxicokinetics and toxicodynamics. Although in vitro data have previously been considered during the risk assessment of food additives, they have generally had no direct influence on the calculation of ADI values. In this review 18 food additives are evaluated for the availability of in vitro toxicity data which might be used for the derivation of a specific data-derived uncertainty factor. For the majority of the food additives reviewed, additional in vitro tests have been conducted which supplement and support the short- and long-term in vivo toxicity studies. However, it was recognized that these in vitro studies could not be used in isolation to derive an ADI; only when sufficient in vivo mechanistic data are available can such information be used in a regulatory context. Additional short-term studies are proposed for the food additives which, if conducted, would provide data that could then be used for the calculation of data-derived uncertainty factors.

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.

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.

Urine levels of aluminum after drinking tea

A microwave-assisted acid digestion procedure coupled with a graphite furnace atomic absorption method has been applied in the determination of aluminum (Al) in urine to verify the correlation of free forms of Al in tea infusions and urinary excretion of Al. Significant urinary Al excretion has been found in 24-h urine of four volunteers after tea drinking. However, the difference in amount of Al excretion in urine between the consumption of Oolong (black tea) and Long-Jin (green tea), each of them with unique Al contents and species, was not significant. These findings indicated that the high levels of free Al species in tea infusions did not result in significant change in urinary excretion of the metal, possibly owing to the transformation by ligands present in food and the gastrointestinal tract (GIT). However, it could not be assumed that there was no big difference in absorption of the metal in the human body if fractions of consumed Al retained in the body or excreted by bile or feces were considered.

Effect of small variations of aluminum intake on calcium metabolism in young rats

BACKGROUND

While in the adult Al intoxication requires high dosages, little is known on the threshold level of Al toxicity in the young.

METHODS

Weaning rats were fed for 90 days ore of four diets differing by their content in Ca (7.5 vs < 0.5 g/< g diet)(Ca+/-) and Al (10.6 vs 8.4 mg/kg)(Al+/-); Al supplementation was 30% above the standard level of diet. Ca and Al levels were measured in liver, bone (femur), and brain.

RESULTS

Ca- had a significant negative effect on growth which was further reduced by Al+; in Ca sufficient/Al+ animals, Al concentrations were significantly increased in bone and brain and tended to increase in liver; Ca decreases observed in these three organs were only significant in brain. Ca deficiency further enhanced the Al deposit in bone at both levels of Al intakes, and reduced Ca concentrations in these three organs in Al+ animals; in Ca-/Al- animals, the decrease in Ca displayed in the three tissues reached a significant level in brain.

CONCLUSIONS

This study suggests that in the growing subject the side effects of small variations of Al intake can be enhanced when they are combined with other mineral imbalances.

The bioavailability of 26Al-labelled aluminium citrate and aluminium hydroxide in volunteers

A study was undertaken to determine the fraction of ingested aluminium taken up by two male volunteers, following their ingestion of either aluminium citrate or aluminium hydroxide. In addition, the effects of simultaneous citrate ingestion on the gastrointestinal absorption of aluminium from its hydroxide was studied. Volunteers received three oral doses of 26Al-labelled aluminium compound in water. The doses were administered directly into the stomach using a paediatric feeding tube. Blood samples were collected from the volunteers at 1, 4 and 24 h after administration, and their daily output of urine and faeces was collected for 6 days. These samples were analysed for their 26Al content using either coincidence gamma-counting or accelerator mass spectrometry. The uptake of aluminium was greatest following its administration in the citrate form and was least following intake as the aluminium hydroxide suspension. The co-administration of citrate, with the aluminium hydroxide suspension, was found to enhance the levels of 26Al uptake in both volunteers. Using a urinary excretion factor based on the results of previous studies, the fractional aluminium uptake from each of the species was calculated: aluminium citrate, 5.23 x 10(-3); aluminium hydroxide, 1.04 x 10(-4); aluminium hydroxide with citrate, 1.36 x 10(-3).

Chronic effect of aluminium ingestion on bone in calcium-deficient rats

In order to elucidate the relationship of osteogenesis with aluminum and iron deposition, we investigated the histopathological findings of bone in calcium and/or aluminium-deficient rats, together with levels of calcium, aluminium and iron in sera and bone tissues, and also the level of serum parathyroid hormone. Four week old male STD-Wistar rats were divided into four groups to examine the effects of four kinds of diets for ten weeks. The rats on normal diet (Group I) and normal diet+aluminum (Group II) did not show any pathological changes of the bones, but in both calcium-deficient diet group (Group III) and calcium deficient diet added aluminium (Group IV), the compact bone converted into spongy bone in varying degrees, particularly in Group IV. Aluminium deposition was demonstrated at the calcification fronts and the cement lines only in Group IV as red or violet-red lines with aluminium stain, together with iron deposition as revealed with Berlin blue stain, showing similar distribution pattern as aluminum. It was clearly indicated that aluminium and iron, instead of calcium, deposited on the calcification front of the bone under the condition of calcium deficiency, inhibiting the normal osteogenesis.

Aluminum exposure and excretion

Occupational exposure to aluminum can be associated with increases in both urinary aluminum excretion and serum aluminum. In most studies, the increases in urinary aluminum are proportionately greater than the changes in serum aluminum. A similar pattern of response follows increases in dietary aluminum intake. Thus, there is ample evidence for systemic aluminum absorption from occupational exposure to airborne aluminum as well as dietary intake. Although both circumstances are accompanied by a similar renal response, there is little information explaining how normal kidneys augment renal excretion with only trivial changes in serum aluminum concentrations. In addition, it is not understood how airborne exposure to microgram amounts of aluminum produces significant increases in urinary aluminum. The latter observation suggests the presence of a sensitive uptake process for aluminum from airway exposure.

Estimates of dietary exposure to aluminium

Daily intakes of aluminium were estimated for 14 age-sex groups based on the Food and Drug Administration's (FDA) Total Diet Study dietary exposure model. The aluminium content of the core foods of the FDA Total Diet Study were determined by analyses, recipe calculation, or literature values and coupled with information on food consumption from the 1987-88 US Department of Agriculture Nationwide Food Consumption Survey. Estimates of aluminium intakes ranged from 0.7 mg/day for 6-11-month-old infants to 11.5 mg/day for 14-16-year-old males. Average intakes for adult men and women were 8-9 and 7 mg/day, respectively. The major contributors to daily intake of aluminium were foods with aluminium-containing food additives, e.g. grain products and processed cheese.

Gastro-intestinal availability of aluminium from tea

The in vitro speciation of aluminium (Al) in black tea infusion (pH 4.8) was assessed using 3000, 10,000 and 30,000 Da cut-off ultrafilters, and the effect of adding human gastric juice (pH 2.3) and then raising the pH to 6.5 were also studied. 78% Al in the tea infusion passed through the 3000-Da ultrafilter; this percentage increased to more than 90% with the addition of gastric juice at pH 2.3, but then reduced to approximately 5% when the incubate was adjusted to pH 6.5. The breakdown of tea-derived polyphenols to low molecular weight phenols in vivo was measured using high-resolution 1H nuclear magnetic resonance spectroscopic analysis of ileostomy effluent, but there was no evidence of low molecular weight breakdown products from the polyphenols of ingested tea in this effluent. These results suggest that only a small proportion of Al in tea is potentially available for absorption throughout the small bowel. It may be misleading to estimate systemic Al absorption from tea drinking simply from total urinary aluminium excretion as has been done previously.

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.

Measurement of aluminium in clinical samples

Measurement of aluminium in clinical samples is important for the protection of patients with chronic renal failure, and for investigations of dementia. The types of specimen that need to be analysed include body fluids and tissues, dialysis fluids, water and foods and the concentrations that may be found can range from around 1 microgram/L to several mg/L. Although techniques must afford exceptional sensitivity they will also be susceptible to the effects of external contamination and it is imperative that those involved with the analysis, from sample collection through to the determination, ensure that precautions are taken to prevent undue addition of the metal. Of the methods that may be used ETAAS is clearly the most appropriate. Great care is required to achieve reliable performance but with experienced personnel very good results can be obtained. Regular reviews of recent analytical developments are presented in the Atomic Spectrometry Updates series and these are recommended to those who may wish to look for further information.

Aluminum toxicity in childhood

Aluminum intoxication is an iatrogenic disease caused by the use of aluminum compounds for phosphate binding and by the contamination of parenteral fluids. Although organ aluminum deposition was noted as early as 1880 and toxicity was documented in the 1960s, the inability to accurately measure serum and tissue aluminum prevented delineation of its toxic effects until the 1970s. Aluminum toxicity has now been conclusively shown to cause encephalopathy, metabolic bone disease, and microcytic anemia.

Aluminium levels in milk and infant formulae

Aluminium levels in infant formulae purchased in 1990 and prepared as for consumption were in the range 530 micrograms/l to 640 micrograms/l for soya-based products and 27 micrograms/l to 120 micrograms/l for cows' milk-based formulae. Mean aluminium concentrations in these soya and cows' milk-based samples were, on average, 37% and 45% lower, respectively, than those of the same brands purchased between 1985 and 1987. Levels of aluminium in breast milk were in the range 3 micrograms/l to 79 micrograms/l. In the case of retail cows' milk, values ranged from 4 micrograms/l to 33 micrograms/l whilst more variable amounts of between 5 micrograms/l and 285 micrograms/l were detected in retail soya milk.

Aluminium deposition in bone after contamination of drinking water supply

Two healthy individuals who drank water accidentally contaminated at source with aluminium sulphate solution were investigated 6-7 months later. Bone biopsy specimens showed discrete lines of positive staining for aluminium, the distribution being compatible with acute exposure some months previously. These findings show that under certain conditions normal individuals can absorb aluminium via the gut, and that such aluminium can be deposited in bone.