Molybdenum exposure

The primary pathway for molybdenum exposure is ingestion by water or food. Molybdenum is found in leafy vegetables, legumes, meat, and many grains. Molybdenum does not appear to be absorbed der-mally. Dusts and fumes may be inhaled. In ambient air in urban areas, molybdenum ranged from 0.01 to 0.03 pgm, and in nonurban areas it varied between 0.001 and 0.0032 pg m ... 

Reid SD (2002) Physiological impact of acute molybdenum exposure in juvenile kokanee salmon (Oncorhynchus nerka). Comparative Biochemistry and Physiology. Toxicology Pharmacology CBP 133 355-367. 

The endemic disease is characterized by severe scouring and impaired condition in cattle. Molybdenum exposure leads to copper depletion and in turn secondary copper deficiency hence, the copper and sulfur supply of animals is of major importance. Inorganic molybdenum compounds, in the presence of sulfite, are converted to thiomolybdates (e.g., tetrathiomolybdate MoS ) by microorganisms in the rumen. The thiomolybdates then react rapidly with particulate matter and proteins to form complexes that bind copper strongly. Bioassays... 

Molybdenum exposure also reduced the fertility of bulls (Thomas and Moss 1951), heifers and cows (Phillippo et al. 1982, 1985a, b. Case and Selby 1973), billy-goats (Anke and Masaoka 1988), rabbits (McCarter et al. 1962, Kroupova et al. 1989), and male rats (Pandey and Singh 2002). Molybdenum-loaded bUly-goats (1000 mgkg food DM) produced sperm with low mobility and fecundation (Anke and Masaoka 1988, Falke and Anke 1987). 

The outcome seemed due to a particular effect of molybdenum exposure rather than to secondary copper deficiency. The reduction in peak levels of ovulatory luteinizing hormone suggested that events controlling estrus and sexual interest in males had been altered by molybdenum. These effects were the consequence of an inhibitory influence of molybdenum on estrogen and androgen receptor activity that had been demonstrated in cell culture. The effects of sodium molybdate have been described for estrogen receptors (Joab etal. 

The effects of molybdenum exposure are species-specific. Cattle reacted to molybdenum exposure most sensitively, followed by sheep and other species of wild ruminants. Horses and pigs tolerated molybdenum to a greater level, whilst in experiments conducted in the author s laboratory, goats proved to be particularly molybdenum-toler-... 

High molybdenum content in the feed can lead to bone deformities in cattle, sheep, rabbits, and rats. The reason for this is secondary copper deficiency as it was shown in cattle. Molybdenum exposure also reduces the fertility of heifers and cows [40,41], But this does not seem to be due to an effect of secondary copper deficiency but to a particular effect of molybdenum exposure. In bulls and he-goats molybdenum intake led to the loss of sexual libido and to damage of interstitial cells and germinal epithelium [39]. 

Under unusual circumstances, toxicity may arise from ingestion of excess amounts of minerals. This is uncommon except in the cases of fluorine, molybdenum, selenium, copper, iron, vanadium, and arsenic. Toxicosis may also result from exposure to industrial compounds containing various chemical forms of some of the minerals. Aspects of toxicity of essential elements have been pubhshed (161). 

With the exception of iron(II) and uranium(IV), the reduced solutions are extremely unstable and readily re-oxidise upon exposure to air. They are best stabilised in a five-fold excess of a solution of 150g of ammonium iron(III) sulphate and 150 mL of concentrated sulphuric acid per litre [approximately 0.3M with respect to iron] contained in the filter flask. The iron(II) formed is then titrated with a standard solution of a suitable oxidising agent. Titanium and chromium are completely oxidised and produce an equivalent amount of iron(II) sulphate molybdenum is re-oxidised to the Mo(V) (red) stage, which is fairly stable in air, and complete oxidation is effected by the permanganate, but the net result is the same, viz. Mo(III)- Mo(VI) vanadium is re-oxidised to the V(IV), condition, which is stable in air, and the final oxidation is completed by slow titration with potassium permanganate solution or with cerium(IV) sulphate solution. 

Glocker and Frohnmayer determined the characteristic constant c for nine elements (Reference 2, Table 4) ranging in atomic numbers from 42 (molybdenum) to 90 (thorium). They proved that identical results could be obtained with the sample in the primary (polychromatic) or in the diffracted (monochromatic) beam. The method was applied with good results to the determination of barium in glass of antimony in a silicate of hafnium in the mineral alvite and of molybdenum, antimony, barium, and lanthanum in a solution of their salts—for example, 5.45% barium was found on 90-minute exposure by the x-ray method for a glass that yielded 5.8% on being analyzed chemically. 

It is clear that both the form of molybdenum administered and the route of exposure affect molybdenum metabolism and survival (Table 30.4). By comparison, adverse effects (some deaths) were noted at 250 mg Mo/kg body weight (BW) (in guinea pigs), at 50 mg/kg BW in domestic cats (central nervous system impairment), at 10 mg/L drinking water in mice (survival), at 10 to 15 mg total daily intake in humans (high incidence of gout-like disease), and at to 3 mg/m3 air in humans for 5 years (respiratory difficulties), or 6 to 19 mg/m3 in humans for 4 years (Table 30.4). 

Strontium, barium, manganese, copper, molybdenum, and nickel are elements of strong accumulation in plant species of African Savanna ecosystems, in spite of different content in soils and soil-forming rocks. The Cb values are >1. The other elements, like beryllium, zirconium, titanium and vanadium, are less taken up by plants and their Cb values are less than 0.5. These refer to various exposure pathways to both microbes and plants as links in biogeochemical food webs. 

A 0.4 m thick SPP layer was exposed to X-rays followed by a flood exposure using near UV radiation. The resist was then dip-developed in a 0.8 wt% TMAH solution for 60 s at 25 °C. We used two x-ray exposure systems to evaluate the characteristics of the SPP resist. One is SR-114 which has a source composed of a molybdenum rotating anode with a 0.54 nm Mo-La characteristic line. The exposure was carried out in air. The other has a synchrotron radiation source with a central wavelength of 0.7 nm (KEK Photon Factory Beam Line, BL-1B). The exposure was carried out in vacuum (<10-4 Pa). A positive resist, FBM-G,15) was used as a standard, because its sensitivity only weakly depends on the ambient. 

Type 2. An example of this is molybdenum (22), where interaction is clearly dissociative [0(1 s) value of 530.3 eV] at 295 K. Further exposure to water vapor results in molecular adsorption [0(ls) value 533 eV],... 

Colorimetric field tests for TATP and HMTD were described in Section 5 dealing with peroxide-based explosives. This group contains Keinan s PEX [85] (E. Keinan, Personal Communication, February 2006) and the kit developed by Schulte-Ladbeck et al., which involves also a preliminary stage to avoid falsepositive responses by non-explosive peroxides [86]. The color change of molybdenum hydrogen bronze suspension upon reaction with TATP was recommended also as a field test. Exposure of filter paper strips which were soaked in butanol suspension of the molybdenum compound to TATP or hydrogen peroxide vapors rapidly bleaches the blue color [87, 88]. 

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