Barium compounds are absorbed via ingestion and inhalation, the extent of which depends on the individual compound. In the body, the majority of the barium is found in the bone, while small amounts exists in the muscle, adipose, skin, and connective tissue. Barium is not metabolized in the body, but it may be transported or incorporated into complexes or tissues. Barium is excreted in the urine and faeces. Aluminum is poorly absorbed following either oral or inhalation exposure and is essentially not absorbed dermally. The bioavailability of aluminum is strongly influenced by the aluminum compound and the presence of dietary constituents which can complex with aluminum and enhance or inhibit its absorption. Aluminum binds to various ligands in the blood and distributes to every organ, with highest concentrations found in bone and lung tissues. In living organisms, aluminum is believed to exist in four different forms: as free ions, as low-molecular-weight complexes, as physically bound macromolecular complexes, and as covalently bound macromolecular complexes. Absorbed aluminum is excreted principally in the urine and, to a lesser extent, in the bile, while unabsorbed aluminum is excreted in the faeces. (L739, L214)
Barium is a competitive potassium channel antagonist that blocks the passive efflux of intracellular potassium, resulting in a shift of potassium from extracellular to intracellular compartments. The intracellular translocation of potassium results in a decreased resting membrane potential, making the muscle fibers electrically unexcitable and causing paralysis. Some of these barium's effects may also be due to barium induced neuromuscular blockade and membrane depolarization. The main target organs of aluminum are the central nervous system and bone. Aluminum binds with dietary phosphorus and impairs gastrointestinal absorption of phosphorus. The decreased phosphate body burden results in osteomalacia (softening of the bones due to defective bone mineralization) and rickets. Aluminum's neurotoxicity is believed to involve several mechanisms. Changes in cytoskeletal protein functions as a results of altered phosphorylation, proteolysis, transport, and synthesis are believed to be one cause. Aluminum may induce neurobehavioral effects by affecting permeability of the blood-brain barrier, cholinergic activity, signal transduction pathways, lipid peroxidation, and impair neuronal glutamate nitric oxide-cyclic GMP pathway, as well as interfere with metabolism of essential trace elements because of similar coordination chemistries and consequent competitive interactions. It has been suggested that aluminum's interaction with estrogen receptors increases the expression of estrogen-related genes and thereby contributes to the progression of breast cancer (A235), but studies have not been able to establish a clear link between aluminum and increased risk of breast cancer (A15468). Certain aluminum salts induce immune responses by activating inflammasomes. (L739, A235, A236, L214)
Not listed by IARC. IARC classified aluminum production as carcinogenic to humans (Group 1), but did not implicate aluminum itself as a human carcinogen. (L135) A link between use of aluminum-containing antiperspirants and increased risk of breast cancer has been proposed (A235), but studies have not been able to establish a clear link (A15468).
The health effects of the different barium compounds depend on how well the compound dissolves in water or the stomach contents. At low doses, barium acts as a muscle stimulant, while higher doses affect the nervous system, causing cardiac irregularities, tremors, weakness, anxiety, dyspnea, paralysisand possibly death. Barium may also cause gastrointestinal disturbances, damage the kidneys and cause decreases in body weight. Aluminum targets the nervous system and causes decreased nervous system performance and is associated with altered function of the blood-brain barrier. The accumulation of aluminum in the body may cause bone or brain diseases. High levels of aluminum have been linked to Alzheimer’s disease. A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminium. (L739, L740, L214)
Ingesting excess barium may cause vomiting, abdominal cramps, diarrhea, difficulties in breathing, increased or decreased blood pressure, numbness around the face, and muscle weakness. High levels may result in changes in heart rhythm or paralysis and possibly death. Inhalating aluminum dust causes coughing and abnormal chest X-rays. A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminium. (L739, L740, L214)
