The health effects of aluminum compounds in mammals

A review on management of waste three-way catalysts and strategies for recovery of platinum group metals from them

Platinum group metals (PGMs), especially platinum (Pt), palladium (Pd), and rhodium (Rh), are widely used in automotive three-way catalysts (TWCs). PGM resources are scarce and unevenly distributed, with global reserves of 69,000 t in 2020, of which more than 99% are concentrated in South Africa, Russia, Zambia, and the United States. However, the demand for PGMs worldwide is growing continually, especially in China. The recovery of PGMs from spent TWCs not only can alleviate the contradiction between supply and demand but also have good economic and environmental benefits. This paper briefly analyzes the market demand for Pt, Pd, and Rh in the global automotive industry in recent years, emphasizing the importance of waste TWC recycling. It also presents the current status of waste TWC management in some countries, especially China, and critically reviews the main recycling strategies for waste TWCs. On this basis, suggestions for strengthening the management of waste TWCs in China are put forward, and the future development trend of recycling technology is foreseen. The purpose of this paper is to provide some valuable references for the decision-makers of waste TWC management, and hopefully to provide inspiration for related scholars on the future research direction of waste TWC recycling technology.

Mineral balance in horses fed two supplemental silicon sources

Numerous studies suggest that silicon (Si) supplementation is beneficial for mineral metabolism and bone health. Mineral balance studies have not been performed in horses to determine how these supplements affect absorption of other minerals. The purpose of these studies was to investigate the effects of two different Si supplements on mineral absorption and retention in horses. Eight geldings were randomly placed in one of two groups: control (CO) or supplemental Si, which was provided by one of two supplements. The first, sodium aluminium silicate (SA), contains a bioavailable form of Si and is high in aluminium (Al). The second supplement contains oligomeric orthosilicic acid (OSA). All horses received textured feed and ad libitum access to hay. Supplemented horses received either 200 g of SA or 28.6 ml of OSA per day. Following a 10-day adaptation period, the horses underwent a 3-day total collection. Blood samples were taken on days 0 and 13. The two balance studies were conducted 4 months apart to reduce carryover effects. Intakes of Al and Si were greater with SA supplementation (p < 0.05). Sodium aluminium silicate increased faecal and urinary Si excretion (p < 0.05). Calcium retention and apparent digestion were increased by SA (p < 0.05). It also maintained plasma Si compared with the CO which tended to have a decrease in plasma Si (p = 0.08). Supplemental OSA increased retention of Ca and B (p < 0.05) and apparent digestion of B (p < 0.01). Orthosilicic acid tended to increase Si retention (p = 0.054), apparent digestion (p < 0.065), and also increased plasma Si. Both supplements were able to alter Ca retention and B metabolism, however, only OSA was able to alter Si retention, digestibility and plasma concentration. Orthosilicic acid, an Si supplement without substantial Al, appears to be a viable option for Si supplementation as it increased Si retention and digestibility.

Clearance and translocation of aluminum oxide (alumina) from the lungs

Significant respiratory-tract exposure to insoluble aluminum compounds, such as alumina (aluminum oxide, Al(2)O(3)), can occur in occupational settings, yet little is known about the temporal pattern of pulmonary clearance of these materials from the lungs with repeated exposures, and potential subsequent translocation to other organs. This study evaluated the clearance pattern of alumina from the lungs of rats, and burdens in selected extrapulmonary organs (brain, bone, liver, spleen, kidney). Rats were instilled with alumina once weekly for 20 wk. Quantification of retention was performed by measuring aluminum burdens in the lungs and extrapulmonary organs during the exposure period, and then weekly for an additional 19 wk after the exposures ended. Lung burdens of aluminum were found to steadily increase during exposure. Clearance of the material following the end of the exposure regime was extremely slow; only approximately 9% of the amount in the lungs following the 20 weekly exposures was cleared by the end of the postexposure period. This study supports the concept of gradual accumulation and long-term retention of aluminum within the respiratory tract of individuals repeatedly exposed to alumina in occupational settings.

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.

Regional alterations in calcium homeostasis in the primate brain following chronic aluminium exposure

The present study investigates the possible effects of chronic aluminium exposure on the various aspects of calcium homeostasis in the primate central nervous system. Aluminium administration caused a marked decline in the activity of Ca2+ ATPase in the monkey brain. The total calcium content was also significantly raised following aluminium exposure. Concomittant to the increase in the calcium content, the levels of lipid peroxidation were also augmented in the aluminium treated animals, thereby further accentuating the aluminium induced neuronal damage. In addition, aluminium had an inhibitory effect on the depolarization induced 45Ca2+ uptake via the voltage operated channels. The results presented herein, indicate that the toxic effects of aluminium could be mediated through modifications in the intracellular calcium homeostasis with resultant altered neuronal function.

Environmental hazards of aluminum to plants, invertebrates, fish, and wildlife

Aluminum is extremely common throughout the world and is innocuous under circumneutral or alkaline conditions. However, in acidic environments, it can be a major limiting factor to many plants and aquatic organisms. The greatest concern for toxicity in North America occurs in areas that are affected by wet and dry acid deposition, such as eastern Canada and the northeastern U.S. Acid mine drainage, logging, and water treatment plant effluents containing alum can be other major sources of Al. In solution, the metal can combine with several different agents to affect toxicity. In general, Al hydroxides and monomeric Al are the most toxic forms. Dissolved organic carbons, F, PO(3)3- and SO(4)2- ameliorate toxicity by reducing bioavailability. Elevated metal levels in water and soil can cause serious problems for some plants. Algae tend to be both acid- and Al tolerant and, although some species may disappear with reduced pH, overall algae productivity and biomass are seldom affected if pH is above 3.0. Aluminum and acid toxicity tend to be additive to some algae when pH is less than 4.5. Because the metal binds with inorganic P, it may reduce P availability and reduce productivity. Forest die-backs in North America involving red spruce, Fraser fir, balsam fir, loblolly pine, slash pine, and sugar maples have been ascribed to Al toxicity, and extensive areas of European forests have died because of the combination of high soil Al and low pH. Extensive research on crops has produced Al-resistant cultivars and considerable knowledge about mechanisms of and defenses against toxicity. Very low Al levels may benefit some plants, although the metal is not recognized as an essential nutrient. Hyperaccumulator species of plants may concentrate Al to levels that are toxic to herbivores. Toxicity in aquatic invertebrates is also acid dependent. Taxa such as Ephemeroptera, Plecoptera, and Cladocera are sensitive and may perish when Al is less than 1 mg.L-1 whereas dipterans, molluscs, and isopods seem to be tolerant. In Al-sensitive species, elevated levels (approximately 500 micrograms.L-1) affect ion regulation and respiratory efficiency. Toxicity tends to be greatest near a species' threshold of pH sensitivity. At lower pHs, Al may have a slight ameliorative effect by interfering with H+ transport across membranes. Aquatic invertebrates can accumulate very high levels of Al, but most of this appears to be through adsorption rather than assimilation. Aluminum concentrations may be as high as 5000 mg.kg-1 in insects and greater than 17,000 mg.kg-1 in other invertebrates.(ABSTRACT TRUNCATED AT 400 WORDS)

Hematological effects of aluminum on living organisms

1. Aluminum has been of great interest for many researchers over a number of years; its biochemical and physiological role is not yet fully clear. There are few papers describing the hematological consequences of its excess in living organisms and most of their data are cited in this paper. 2. Aluminum reduced the deformability of erythrocytes, and such cells are rather frequently retained in the reticuloendothelial system of the spleen and eliminated faster from the blood stream. 3. Aluminum produces peroxidative changes in the erythrocytes membrane, leading to hemolysis. Therefore, the depressed erythrocyte count in animals intoxicated with aluminum may be the consequence of both the hemolytic action of aluminum and the shortened time of survival of erythrocytes. 4. It was demonstrated that aluminum inhibits heme biosynthesis in vitro. This problem requires, however, further studies and observation. 5. Changes occurring under the influence of Al3+ on the leukocyte system of animals suggest the influence of this element on the resistance of the organism, but the mechanism of the action of Al3+ still requires elucidation. 6. Cell metabolism including blood cells may be affected by aluminum in many ways, the more so as the element may combine in vitro with amino acids, peptides, proteins, enzymes, substrates, cofactors, nucleotides and carbohydrates. Aluminum stimulates NADPH oxidation and takes part in the process of free radical formation.

Serum concentrations of calcitriol and PTH in hemo-dialysis patients on treatment with calcium carbonate

The effects of calcium carbonate and aluminium hydroxide as phosphate binders were investigated in nine patients on chronic hemodialysis. Aluminium hydroxide, 1 g X 3, was given during four weeks followed by a period of four weeks without any phosphate binders and after this calcium carbonate, 2.5 g X 3, was introduced for four weeks. Calcium carbonate resulted in lowering of bioactive PTH in serum from 22.4 to 16.4 pM and a rise of serum calcitriol from 8.0 to 11.5 pg/ml with maintained control of phosphate and without significant difference in the calcium-phosphate product. Calcium in serum rose from 2.27 to 2.57 mM and mild hypercalcemia (less than 3.0 mM) in five of the patients could be controlled by dose reduction of calcium carbonate without losing control of serum phosphate levels. We conclude that calcium carbonate offers advantages as a phosphate binder compared to aluminium hydroxide in that it offers equal control of serum phosphate and elevates serum calcium which helps to control the hyperparathyroidism secondary to uremia.

Effects of acidification on the availability of toxic metals and calcium to wild birds and mammals

The effects of acidification on wildlife inhabiting aquatic or semi-aquatic environments are reviewed, with particular reference to the possibility for increased dietary exposure to Hg, Cd, Pb and/or Al, and decreased availability of essential dietary minerals such as Ca. It is concluded that: (1) piscivores risk increased exposure to dietary methyl-Hg in acidified habitats, and Hg concentrations in prey may reach levels known to cause reproductive impairment in birds and mammals; (2) piscivores do not risk increased exposure to dietary Cd, Pb or Al because these metals are either not increased in fish due to acidification, or increase are trivial from a toxicological perspective; (3) insectivores and omnivores may, under certain conditions, experience increased exposure to toxic metals in some acidified environments. Exposure levels are likely to be sufficiently low, however, that significant risks to health or reproduction are unlikely. More importantly, these wildlife species may experience a drastic decrease in the availability of dietary Ca due to the pH-related extinction of high-Ca aquatic invertebrate taxa (molluscs, crustaceans). Decreased availability of dietary Ca is known to adversely affect egg laying and eggshell integrity in birds, and the growth of hatchling birds and neonatal mammals. Acidification-related changes in the dietary availability of other essential elements, such as Mg, Se and P, have not been established and require further investigation; (4) herbivores may risk increased exposure to Al and Pb, and perhaps Cd, in acidified environments because certain macrophytes can accumulate high concentrations of these metals under acidic conditions. The relative importance of pH in determining the metal concentrations of major browse species, and the toxicological consequences for herbivores wildlife, is not well established and requires further study. A decreased availability of dietary Ca is also likely for herbivores inhabiting acidified environments.

Human exposure to aluminum

Aluminum is the third most abundant element in nature, accounting for nearly 8% of the Earth's crust. Because of its chemical activity, aluminum is not found naturally in its "free", or metallic, state. However, in its ionic or combined forms, aluminum is a truly ubiquitous element.Because of the widespread use of metallic aluminum in cooking and packaging applications, the Aluminum Association has funded critical reviews of the world's literature on the health effects of aluminum and aluminum compounds for the past 30 years.More recently, an extensive research and literature surveillance effort was developed to provide information on the neurological implications of aluminum, dietary intakes and body balance, and analytical capabilities. Based on these efforts the following conclusions can presently be drawn: (1) the cause (or causes) of Alzheimer's disease is not known; (2) the biological significance of aluminum found in the brain is not understood; (3) aluminum is poorly absorbed by the body; and (4) the normal ingestion of aluminum from food and water should have no adverse effects on human health.

Environmental effects of aluminium

Aluminium (Al), when present in high concentrations, has for long been recognised as a toxic agent to aquatic freshwater organisms,i.e. downstream industrial point sources of Al-rich process water. Today the environmental effects of aluminium are mainly a result of acidic precipitation; acidification of catchments leads to increased Al- concentrations in soil solution and freshwaters. Large parts of both the aquatic and terrestrial ecosystems are affected.In the aquatic environment, aluminium acts as a toxic agent on gill-breathing animals such as fish and invertebrates, by causing loss of plasma- and haemolymph ions leading to osmoregulatory failure. In fish, the inorganic (labile) monomeric species of aluminium reduce the activities of gill enzymes important in the active uptake of ions. Aluminium seems also to accumulate in freshwater invertebrates. Dietary organically complexed aluminium, maybe in synergistic effects with other contaminants, may easily be absorbed and interfere with important metabolic processes in mammals and birds.The mycorrhiza and fine root systems of terrestrial plants are adversely affected by high levels of inorganic monomeric aluminium. As in the animals, aluminium seems to have its primary effect on enzyme systems important for the uptake of nutrients. Aluminium can accumulate in plants. Aluminium contaminated invertebrates and plants might thus be a link for aluminium to enter into terrestrial food chains.

Recent developments in aluminum toxicology

Aluminum is now recognised as an important toxin causing considerable morbidity and mortality, particularly in patients with chronic renal failure. Diseases that have been associated with aluminium include dialysis dementia, renal osteodystrophy and Alzheimer's disease. Aluminum also has an effect on red blood cells, parathyroid glands and chromosomes. Accumulation of aluminium in the body tends to occur when the gastrointestinal barrier is circumvented. This has been identified as a problem during dialysis or intravenous fluid administration. Renal functional impairment results in decreased aluminum excretion and promotes accumulation of the element in the body. Many sources have been shown to be contaminated with aluminium. These include the water used for dialysis; medicines containing aluminium, such as aluminium-containing phosphate binding gels; total parenteral nutrition solutions; processed human serum albumin; intravenous fluids in infants; and other environmental and industrial sources. The management of aluminium toxicity involves the identification of these contaminated sources and subsequent removal of the element. This includes regular monitoring of water used in dialysis. The use of aluminium-containing phosphate binding gels in patients with compromised renal function should be reviewed and alternatives sought. The development of effective aluminium-free phosphate binders is desirable. Once a patient has aluminium toxicity, desferrioxamine (deferoxamine) has been shown to be an effective agent in its chelation and removal.

Mutagenicity, carcinogenicity and teratogenicity of aluminium

Aluminium and its salts, which are extensively used in the household and in industry, do not constitute a carcinogenic, mutagenic or teratogenic hazard, except, perhaps, in cases of extremely high exposure. The large majority of the experiments performed to assess the carcinogenicity of aluminium in laboratory animals gave negative results or even suggested some antitumor activity. Moreover, epidemiological studies have not provided clear evidence of a carcinogenic hazard of aluminium to man, and short-term tests made in vitro and in vivo to demonstrate mutagenic activity of A1 were negative except for some experiments in plants. The embryotoxic properties suggested by the studies on birds and mammals could result from the influence of A1 on phosphate and calcium metabolism or from interference with the polymerization of microtubules.

Aluminum and bone disorders: with specific reference to aluminum contamination of infant nutrients

Aluminum (Al) impairment of bone matrix formation and mineralization may be mediated by its direct effect on bone cells or indirectly by its effect on parathyroid hormone and calcium metabolism. Its toxic effects are proportional to tissue Al load. Al contamination of nutrients depends on the amount of Al present naturally in chemicals or from the manufacturing process. Intravenous calcium, phosphorus, and albumin solutions have high Al (greater than 500 micrograms/L), whereas crystalline amino acid, sterile water, and dextrose water have low Al (less than 50 micrograms/L) content. Enteral nutrients including human and whole cow milk have low Al, whereas highly processed infant formulas with multiple additives, such as soy formula, preterm infant formula, and formulas for specific disorders are heavily contaminated with Al. Healthy adults are in zero balance for Al. The gastrointestinal tract excludes greater than 95% of dietary Al, and kidney is the dominant organ for Al excretion. However, even with normal renal function, only 30-60% of an Al load from parenteral nutrition is excreted in the urine, resulting in tissue accumulation of Al. The risk for Al toxicity is greatest in infants with chronic renal insufficiency, recipients of long term parenteral nutrition, i.e., no gut barrier to Al loading, and preterm infants with low Al binding capacity. The rapid growth of the infant would theoretically potentiate Al toxicity in all infants, although the critical level of Al loading causing bone disorders is not known. To minimize tissue burden, Al content of infant nutrients should be similar to "background" levels, i.e., similar to whole milk (less than 50 micrograms/L).

The chronic toxicity of aluminium, cadmium, mercury, and lead in birds: a review

The toxicity of chronic dietary metal exposure in birds is reviewed. It is concluded that significant physiological and biochemical responses to such exposure conditions occur at dietary metal concentrations insufficient to cause signs of overt toxicity. Particularly important are reproductive effects which include decreased egg production, decreased hatchability, and increased hatchling mortality. Young, growing birds are typically more sensitive to the toxic effects of chronic metal exposure than adults, and altricial species are often more sensitive than precocial species. Factors which modify the absorption and toxicity of heavy metals, such as Se for the case of Hg, and Ca for the case of Pb and Cd, are discussed. Monitoring strategies for assessing environmental metal exposure in birds are evaluated.

Aluminum load in chronic intermittent plasma exchange

Aluminum (Al) loading due to administration of human albumin (HA) solutions was studied in 2 patients with stable renal function who underwent plasma exchange once (patient A) and twice (patient B) per week for treatment of hyperviscosity syndrome. Al was determined by Zeeman-AAS in plasma before, during and after treatment, also in bone of one patient and in various preparations of HA from different manufacturers. In addition, the net Al uptake (difference between total Al influx and efflux) and the 24th urinary excretion between 2 exchanges were determined. The electrolyte solution used for dilution had no detectable Al, while HA contained between 15 and 1900 micrograms Al/l. Increase of Al in plasma after treatment was clearly related to Al content of the HA used. When the patients received substitution solutions based on inadvertently highly Al contaminated 20% HA (1419 micrograms/l), the average net uptake was 2265 in patient A and 2049 micrograms in patient B and plasma Al rose from 8.4 respectively 18.0 before to 69.2 and 86.5 micrograms/l after treatment. By using medium Al contaminated HA (574 micrograms/l), the net uptake was 742 (pat. A) and 819 micrograms (pat.B), and there was an elevation of plasma Al from 5.1 respectively 18.2 to 34.2 and 39.8 micrograms/l. Following a net uptake of 870 micrograms patient A excreted 668 micrograms Al until the next treatment (23% positive balance). Treating patient A with a low Al HA (47 micrograms/l), there was a slight increase of plasma Al from 10.8 to 16.2 micrograms/l, the net Al uptake was negligible (less than 10 micrograms), and the weekly Al balance was negative. After 10 months of plasma exchange therapy (patient A) there was no increase of Al in bone (6.4 micrograms/g). We conclude, that the use of HA with a low Al contamination is recommended for all patients receiving this therapy during chronic intermittent plasma exchange or for other indications, especially in cases with impaired renal function.