Toxicological Dangers of Chosen Flame-Retardant Chemical compounds.
PHYSICAL AND CHEMICAL PROPERTIES
The bodily and chemical properties of calcium and zinc molybdates are offered in Desk 9–1.
OCCURRENCE AND USE
Calcium and zinc molybdates are used as flame retardants in cellulosic supplies and different polymers. Textile purposes for calcium and zinc molybdates embrace furnishings, draperies, upholstery seating in transportation automobiles, wall coverings, and carpets (FRCA 1998). Calcium and zinc molybdates are shaped when calcium oxide (CaO) or zinc oxide (ZnO) is complexed with molybdenum trioxide (MoO3). These molybdates readily dissociate within the physique, leading to molybdemum (Mo) in varied valence states, together with zinc and calcium ions (Stokinger 1981). Calcium molybdate can happen naturally because the ore Powellite (Stokinger 1981).
Molybdenum (Mo) exists in six valence states. A very powerful valence states in organic programs are Mo3+, Mo4+, Mo5+, and Mo6+ (Lener and Bibr 1984). Basically, greater oxidation states result in oxygen binding whereas decrease oxidation states favor sulfur or nitrogen binding (EPA 1979). The principal dissolved Mo species within the pure surroundings is molybdate (EPA 1979). The really useful day by day consumption of Mo is 75–250 µg/d (NRC 1989). Mo is essential biologically to people, as it’s a necessary hint component within the Mo-flavoprotein enzyme xanthine oxidase (XO), the place it capabilities as an electron transport agent. XO permits the oxidation of hypoxanthine and xanthine to uric acid. Additionally it is a part of a number of different metalloenzymes, together with aldehyde oxidase and sulfite oxidase (Tsongas et al. 1980).
Zinc is a necessary nutrient with a really useful day by day allowance of 15 mg/d for males and 12 mg/d for females (NRC 1989). The toxicity of zinc in people is taken into account to be fairly low; toxicity usually happens following ingestion of >2 g of zinc (Prasad 1976, as cited in ATSDR 1994).
Calcium is a necessary nutrient, with a really useful day by day allowance of 800–1,200 mg/d relying upon an individual’s age (NRC 1989). No opposed results from consumption of ranges of calcium as much as 2,500 mg/d in wholesome adults have been reported. Excessive calcium intakes might induce constipation, trigger elevated dangers of urinary stone formation in males, and should inhibit the intestinal absorption of iron, zinc, and different important minerals. Ingestion of very giant portions of calcium might end in hypercalciuria, hypercalcemia, and deterioration of renal perform in each sexes (NRC 1989). Further toxicity information on calcium are usually not included on this doc, as a result of the really useful day by day allowance is significantly greater than publicity estimates in flame retardants utilized to upholstery material.
TOXICOKINETICS – “calcium zinc molybdate”
HAZARD IDENTIFICATION1
QUANTITATIVE TOXICITY ASSESSMENT