Calcium toxicity

Calcium is readily abundant in the mammalian diet. A 70 kg human contains approximately 1200 g of calcium and has a daily intake of 1100 mg/day. There are no pubHshed exposure limits (38). Low levels of calcium in the blood, hypocalcemia, can lead to tetany high levels, hypercalcemia, can lead to coma and death. Calcium toxicity, above 160 mg/L in the blood, is not related to an excessive intake of calcium. 

Azmitia, E.C. (1989) Nimodipine attenuates toxicity by MDMA, glutamate and caffeine on serotonergic neurons evidence for a generic model of calcium toxicity. In J. Tra-... 

Caicium (see p 424) usually promptly reverses the depression of cardiac contractility, but It does not affect sinus node depression or peripheral vasodilation and has variable effects on AV nodal conduction. Administer calcium chicride 10%, 10 mL (0.1-0.2 mL/kg) IV, or calcium gluccnate 10%, 20 mL (0.3-0.4 mL/kg) IV. Repeat every 5-10 minutes as needed. In case reports, doses as high as 10-15 g over 1-2 hours and 30 g over 12 hours have been administered without apparent calcium toxicity. 

Precautions in Handling. Ammonium bifluoride, like all soluble fluorides, is toxic if taken internally. Hydrofluoric acid bums may occur if the material comes in contact with moist skin. Ammonium bifluoride solutions should be thoroughly washed from the skin with mildly alkaline soap as soon as possible however, if contact has been prolonged, the affected areas should be soaked with 0.13% solution of Zephiran chloride, or 0.2% Hyamine 1622 (Lonza, Inc.) or calcium gluconate, the treatment recommended for hydrofluoric acid bums. If any of these solutions come in contact with the eyes, they should be washed with water for at least 10 min and a physician should be consulted. 

Health and Safety Factors. The low solubiUty of calcium fluoride reduces the potential problem of fluoride-related toxicity. Water saturated with calcium fluoride has a fluoride concentration of 8.1 ppm as compared to the recommended water fluoridation level of 1 ppm fluoride ion. However, because the solubiUty of calcium fluoride ia stomach acid is higher, continued oral ingestion of calcium fluoride could produce symptoms of fluorosis. The adopted TWA limit for fluorides as F is 2.5 mg/m (68,69). 

Coatings, Paints, and Pigments. Various slightly soluble molybdates, such as those of zinc, calcium, and strontium, provide long-term corrosion control as undercoatings on ferrous metals (90—92). The mechanism of action presumably involves the slow release of molybdate ion, which forms an insoluble ferric molybdate protective layer. This layer is insoluble in neutral or basic solution. A primary impetus for the use of molybdenum, generally in place of chromium, is the lower toxicity of the molybdenum compound. 

Health and Safety Factors. Terephthahc acid has a low order of toxicity. Inhalation by rats for 6 h/d, 5 d/wk for 4 wk produced no fatahties at a dust exposure level of 25 mg/m. The mean acute oral toxicity for rats is over 18 g/kg (86), and for mice over 6 g/kg (87). When terephthahc acid was fed as 3% of the diet to rats, urinary calcuh formed in 90 d, some of which led to cancer. High doses of terephthahc acid lead to formation of calcium terephthalate at levels exceeding its solubihty in urine. This insoluble material leads to the calcuh and provides a threshold below which cancer is not observed (88). Normal precautions used in handling industrial chemicals should be observed with terephthahc acid. If ventilation is inadequate, a toxic-dust respirator should be used to avoid prolonged exposure. 

Proteins and Meals. Nutritional properties of the oilseed protein meals and their derived products are deterrnined by the amino acid compositions, content of biologically active proteins, and various nonprotein constituents found in the defatted meals. Phytic acid (3), present as salts in all four meals, is beheved to interfere with dietary absorption of minerals such as 2inc, calcium, and iron (67) (see Food toxicants, naturally occurring Mineral nutrients). ... 

Health and Safety Factors. The strontium ion has a low order of toxicity, and strontium compounds are remarkably free of toxic hazards. Chemically, strontium is similar to calcium, and strontium salts, like calcium salts, are not easily absorbed by the intestinal tract. Strontium carbonate has no commonly recognized hazardous properties. Strontium nitrate is regulated as an oxidizer that promotes rapid burning of combustible materials, and it should not be stored in areas of potential fire hazards. 

Pantothenic acid toxicity has not been reported in humans. Massive doses (10 g/d) in humans have produced mild intestinal distress and diarrhea. Acute toxicity was observed in case of mice and rats by using calcium pantothenate at fairly large doses (92). 

Vitamin D withdrawal is an obvious treatment for D toxicity (219). However, because of the 5—7 d half-life of plasma vitamin D and 20—30 d half-life of 25-hydroxy vitamin D, it may not be immediately successful. A prompt reduction in dietary calcium is also indicated to reduce hypercalcemia. Sodium phytate can aid in reducing intestinal calcium transport. Calcitonin glucagon and glucocorticoid therapy have also been reported to reduce semm calcium resulting from D intoxication (210). 

Soluble Compounds. The mechanism of barium toxicity is related to its ability to substitute for calcium in muscle contraction. Toxicity results from stimulation of smooth muscles of the gastrointestinal tract, the cardiac muscle, and the voluntary muscles, resulting in paralysis (47). Skeletal, arterial, intestinal, and bronchial muscle all seem to be affected by barium. 

Calcium is a macronutrient essential for all organisms. Chlorine is a micronutrient essential for higher (ie, seed) plants but not considered essential for mammals. Above certain levels chloride is toxic to plants and animals, thus when considering calcium chloride, potentially large concentrations of calcium ion can be tolerated, but at these concentrations the chloride ion becomes toxic. 

Calcium chloride solutions, typically employed at 2—5% concentration, are used as antispasmodics, diuretics (qv), and in the treatment of tetany. Concentrated solutions of calcium chloride cause erythema, exfoUation, ulceration, and scarring of the skin (39). Injections into the tissue may cause necrosis. If given orally calcium chloride can cause irrita tion to the gastrointestinal tract unless accompanied by a demulcent. There is no pubHshed information on mutagenicity or carcinogenicity caused by calcium ions or calcium chloride. Calcium chloride has been given a toxicity or hazard level 3 (40). Materials in this classification typically have LD q below 400 mg/kg or an LC q below 100 ppm. 

Calcium chloride is found in the marine environment. The elemental composition of seawater is 400 ppm calcium, 18,900 ppm chlorine, and many organisms and aquatic species are tolerant of these concentrations. Toxicity arises either from the invasion of freshwater in otherwise saltwater environments or possible toxic doses of calcium chloride from spills, surface mnoff, or underground percolation into typically freshwater streams or aquifers. Various agencies have guidelines for calcium and chloride in potable water (41). The European Economic Community (EEC) is the only agency to have a minimum specification for calcium in softened water. 

The side effects or toxic effects that the calcium antagonists have in common are hypotension, facial flushing, headache, di22iness, weakness, sedation, skin rash, edema, constipation, and abdominal discomfort (nausea, vomiting, and epigastric pressure). 

Ammonium cyanide may be prepared in solution by passing hydrogen cyanide into aqueous ammonia at low temperatures. It may also be prepared from barium cyanide and ammonium sulfate, or calcium cyanide with ammonium carbonate. It may be prepared in the dry state by gentiy heating a mixture of potassium cyanide or ferrocyanide and ammonium chloride, and condensing the vapor in a cooled receiver. Ammonium cyanide is soluble in water or alcohol. The vapor above soHd NH CN contains free NH and HCN, a very toxic mixture. 

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