The debate on tungsten (W) is fostered by its continuous usage in military munitions. Reports demonstrate W solubilizes in soil and can migrate into drinking water supplies and, therefore, is a potential health risk to humans. This study evaluated the reproductive, systemic and neurobehavioral effects of sodium tungstate (NaW) in rats following 70 days of daily pre-and postnatal exposure via oral gavage to 5, 62.5 and 125 mg/kg/day of NaW through mating, gestation and weaning (PND 0-20). Daily administration of NaW produced no overt evidence of toxicity and had no apparent effect on mating success or offspring physical development. Distress vocalizations were elevated in F(1) offspring from the high dose group, whereas righting reflex showed unexpected sex differences where males demonstrated faster righting than females; however, the effects were not dose-dependent. Locomotor activity was affected in both low and high-dose groups of F(1) females. Low-dose group showed increased distance traveled, more time in ambulatory movements and less time in stereotypic behavior than controls or high dose animals. The high-dose group had more time in stereotypical movements than controls, and less time resting than controls and the lowest exposure group. Maternal retrieval was not affected by NaW exposure. Tungsten analysis showed a systemic distribution of NaW in both parents and offspring, with preferential uptake within the immune organs, including the femur, spleen and thymus. Histopathological evidence suggested no severe chronic injury or loss of function in these organs. However, the heart showed histological lesions, histiocytic inflammation from minimal to mild with cardiomyocyte degeneration and necrosis in several P(0) animals of 125 mg NaW dose group. The result of this study suggests that pre and postnatal exposure to NaW may produce subtle neurobehavioral effects in offspring related to motor activity and emotionality.

 

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The use of tungsten as a replacement for lead and depleted uranium in munitions began in the mid 1990's. Recent reports demonstrate tungsten solubilizes in soil and can migrate into drinking water supplies and therefore is a potential health risk to humans. This study evaluated the reproductive and neurobehavioral effects of sodium tungstate in Sprague-Dawley rats following 70 days of daily pre- and postnatal exposure. Adult male and female rats were orally dosed with diH(2)O vehicle, 5 or 125 mg/kg/day of sodium tungstate through mating, gestation, and weaning (PND 0-20). Daily administration of sodium tungstate produced no overt evidence of toxicity and had no apparent effect on mating success or offspring physical development. Distress vocalizations were elevated in the highest dose group. There was no treatment related effect on righting reflex latencies, however, the males had significantly shorter latencies than the females. Locomotor activity was affected in both the low and high dose groups of F0 females. Those in the low dose group showed increased distance traveled, more time in ambulatory movements, and less time in stereotypic behavior than controls or high dose animals. The high dose group had more time in stereotypical movements than controls, and less time resting than controls and the lowest exposure group. Maternal retrieval was not affected by sodium tungstate exposure and there were no apparent effects of treatment on F1 acoustic startle response or water maze navigation. Overall, the results of this study suggest pre- and postnatal oral exposure to sodium tungstate may produce subtle neurobehavioral effects in offspring related to motor activity and emotionality. These findings warrant further investigation to characterize the neurotoxicity of sodium tungstate on dams and their developing pups.

 

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The potential for adverse health effects of using tungsten and its alloys in military munitions are an important concern to both civilians and the US military. The toxicological implications of exposure totungsten, its alloys, and the soluble tungstate (Na(2)WO(4)) are currently under investigation. To examine tungstate toxicity, a series of experiments to determine its in vitro effects on cells of the immune system were performed. We identified alterations in isolated human peripheral blood lymphocytes (PBL) treated in vitro with sodium tungstate (0.01, 0.1, 1.0, and 10 mM). Analyses of apoptosis with annexin V and propidium iodide revealed a dose- and time-dependent increase in the quantity of cells in early apoptosis after tungstate exposure. Reductions in the number of cells entering into the cell cycle were also noted. Exposure of PBL to tungstate (1 mM) and Concanavalin A (ConA) for 72 h reduced the number of cells in S and G(2)/M phases of the cell cycle. There were alterations in the numbers of cells in G(0)/G(1), S, and G(2)/M phases of the cell cycle in long-term THP-1 (acute leukemic monocytes) cultures treated with tungstate (0.01, 0.1, 1.0, and 10 mM). Gel electrophoresis,silver staining, and LC-MS/MS showed the cytoplasmic presence of histone H1b and H1d after 72 h oftungstate exposure. The addition of tungstate to cultures resulted in significant reductions in the quantity of interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha), and IL-6 produced by stimulated [CD3/CD28, ConA, or lipopolysaccharide (LPS)] and tungstate-treated lymphocytes. Taken together, these data indicate that tungstate increases apoptosis of PBL, alters cell cycle progression, reduces cytokine production, and therefore warrants further investigation.

Decomposition of ammonium paratungstate under non-oxidizing atmosphere:

The first stage： 90~180℃，lose crystal water：
5(NH4)2O·12WO3·5H2O=5(NH4)2O·12WO3·H2O+4H2O↑

The second stage: 180 ~ 260 ℃, ammonia loss:
5(NH4)2O·12WO3·H2O=3(NH4)2O·12WO3·3H2O+4NH3↑
Ammonium metatungstate（AMT）

The third stage, 260 ~ 350 ℃, further of lose water and ammonia, ammonium tungsten bronze occurred (ATB):
3(NH4)2O·12WO3·3H2O＝(NH4)2O·12WO3+4NH3↑+5H2O↑

Fourth stage: 350 ~ 450 ℃, ammonia begins to decompose to generate hydrogen and nitrogen:
2NH3 =N2 ↑ + 3H2 ↑
This phase chemical reactions may be
(NH4)2O·12WO3 + H2＝12(NH4)xWO3+H2O+(2-x)NH3↑
(NH4)xWO2.8~3.0

Fifth stage: 450 ~ 550 ℃, ATB decomposition output WO3 and WO2.9

Sixth stage: 550 ~ 650 ℃, decomposition products in addition to small amounts of ATB, there are WO3, WO2.9 and tungsten oxide WO2.72 etc., even WO2.



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Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O. Its shape is like sheet or needle.  It is insoluble in water and alcohol. Ammonium metatungstate is very versatile and can be used as catalysts, capacitors, nuclear shielding, flame retardants, corrosion inhibitors raw materials, but also excellent raw materials in the preparation of ultra fine tungsten powder, tungsten heavy alloy powder, phosphotungstic acid, arsenic acid, silicon tungstate.

Ammonium paratungstate content is listed as below:

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Ammonium paratungstate hydrogen reduction preparing tungsten powder combines the calcination of raw material powder and hydrogen reduction of tungsten oxide. It reduces the intermediate process and improves producing efficiency.

During the process of preparing tungsten powder by ammonium paratungstate hydrogen reduction, reduction temperature and time affects the producing or tungsten powder. Raising reduction temperature and extending reduction time will make the size of tungsten powder bigger and the completion of tungsten powder crystal. Extend the reduction time will make the gaseous phase transport more active. The fine tungsten oxide particles will deposit on the large tungsten powder particles. Thus enlarge the size of grain size.

Compared to the traditional preparing method, tungsten powder prepared by ammonium paratungstate hydrogen reduction has higher property and green strength. 



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Compared to the traditional preparing method, tungsten powder prepared by ammonium paratungstate hydrogen reduction has higher property and green strength. Tungsten powder prepared by this method has uneven particle size and incompletion of crystal. Because of these characters, tungsten powder has greater shaping property and green strength.

Traditional tungsten powder is formed without binder which has low formability. When the pressing pressure is low, the binding strength of powder is insufficient and it is very fragile. It will crack if the pressure rises and cause hierarchy. However tungsten powder prepared by hydrogen reduction under 300MPa, there is no hierarchy and green strength reaches above 2MPa.

Tungsten powder prepared by ammonium paratungstate hydrogen reduction is of irregular shape, during the pressing process, the corner of powder contacts with corner unlike traditional surface contact with surface. The formability thus increases.



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Changing dynamics of four endogenous hormones in normal and aborted ovules of hazelnut（Corylus heterophylla Fisch）was analyzed during fruit development stage，and following ABA and its synthesis inhibitor sodium tungstate solution spraying treatments were carried out to study the effects of ABA on ovules filling process. The results showed that：（1）Content changing curves of IAA，GA₃ and ZR in normal filled ovules were approximately single peak shaped，and their peak value appeared on 80th，90th and 100th day after blooming，respectively. Compared during the same developing period，content of IAA and GA₃ in aborted ovules were lower than that in filled ovules in most cases，while higher ZR content was found to exist in aborted ovules. Eighty to 110 days after blooming was a key period for rapid growth of hazelnut ovule. During the stage，ABA content in developing ovules was significantly higher than that in abortive one.（2）20.0 and 50.0 mg · L^-1 ABA treatments promoted fresh weight of kernel，shell and nut to different degrees，while sodium tungstate had an opposite effects on the above indexes compared with ABA treatments. The results above indicated that ABA was involved in the regulation process of ovule filling in hazelnut.

Tungsten hexafluoride encountered moist air or hydrolyzed, it will emit toxic and corrosive hydrogen fluoride fumes. This smoke will cause very serious injury of people and polluted the environment. Because it has a severe irritant so when during the work the workers should to do all aspects of protection, such as wearing gas masks, protective glasses, wearing protective clothing, in the end of works the workers should to take a shower. The workers who have long been working in such environment should be regular to attend medical examinations.
If accidentally the tungsten hexafluoride leak, all the stuff should be rapid withdrawal from leaking area to a safe area, not to prohibit access to the contaminated area, emergency personnel wearing self-contained breathing apparatus and chemical protective clothing (to ensure complete segregation). In ensuring the safety of plugging, then slowed tungsten hexafluoride volatile by spraying water, but not to directly spray to leak point. Do not allow water to enter the packaging container, drainage (indoor), or powerful ventilation (outdoor). Leaking containers cannot use, and to remove any residual gas through the technical processing.

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Heavy tungsten oxide has several trade names: methenamine, tungsten powder, tungsten oxide and heavy network potassium. Heavy tungsten chemical oxide formula is (CH2) 6N4, industry hexamethylene tetramine of scientific name. It is a white crystalline powder, has a stimulating effect on the skin, the proportion of 1.27 (25 ℃) was dissolved in water, ethanol and chloroform, insoluble in ether, easily agglomerate with moisture, and it can burning a lot of heat when it burn with fire, the combustion flame is colorless.
Heavy tungsten oxide is mainly used in produce phenolic curing agent, aminoplast catalyst, rubber vulcanization accelerator, anti-shrinking agents in the textile industry, the pharmaceutical industry diuretic, urinary antiseptic, military and the RDX explosives and raw material of agricultural pesticides. Heavy tungsten oxide mixed with caustic soda and phenol can be used as masks for phosgene absorber.

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