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Tungsten, chemical symbol W (for Wolframite, its mineral form's German name) - atomic number 74 - is a widely used metal that has a very high tensile strength and melting point. It is used in its elemental form in military guns and projectiles, wear-resistant machinery/products, lightbulb filaments and electron and television tubes. Compounds of tungsten are used in fluorescent lighting tubes, in the chemical and tanning industries and, as tungsten disulfide, in industrial lubricants. Although the medical literature on the toxic effects of tungsten is limited, a review of available literature reveals major concerns about the long-term risk to health of tungsten and tungsten compounds.
Acute tungsten poisoning
This is an extremely rare presentation. Much of the information on human toxicity comes from case reports of a purported acute toxic reaction to tungsten dissolved in alcoholic drinks following a tradition of French army artillery recruits drinking wine/beer which had rinsed a recently fired gun barrel. Introduction of tungsten into the alloy of the barrel was thought to be the cause of this novel poisoning event. Toxicological analysis confirmed grossly elevated levels of tungsten in blood, urine, hair and nails. Clinical features of this acute episode included:
- Acute nausea within 15 minutes of ingestion.
- Sudden onset of seizures.
- Rapid onset of clouded consciousness leading to coma with evidence of encephalopathy.
- Initial moderate renal failure progressing to acute tubular necrosis with anuria within 24 hours
- Gradual symptomatic recovery over weeks with complete resolution of biochemical/metabolic abnormalities after 5 months
Elemental tungsten is often produced in a powdered form so there is a theoretical risk of acute toxicity from inhaling the substance in this form or from machine wear/artillery disruption, although there are no reports of this form of acute poisoning.
Chronic tungsten poisoning
- Hard metal workers (involved, for example, in grinding metals) and soldiers with embedded shrapnel may be exposed to the risk of long-term tungsten exposure.
- Tungsten may be implicated in cases of pulmonary fibrosis due to hard metal lung disease. This giant cell interstitial pneumonitis is contracted from inhaling the dust formed from the manufacture, utilisation or maintenance of hard metal, a material composed of tungsten carbide and cobalt. However, it appears that the vast majority of the toxicity is attributable to the effects of cobalt on respiratory tissues in susceptible individuals.
- Similarly, a dermatitis in hard metal workers appears to be due largely to the effects of cobalt. It has, however, been noted that tungsten carbide appears to modify the toxicity of cobalt and that cobalt alone does not have the same potent toxic effects.
- Hard metal workers have also shown evidence of mild-to-moderate neuropsychological impairment, particularly with regard to memory function.
- However, a lack of chronic toxicity of tungsten in isolation would appear to be supported by studies into its effects following ingestion by birds. It is used as an alternative to lead for shotgun pellets, to prevent toxic effects when ingested by wildfowl, and appears to cause them no significant harm in chronic dosing studies. These studies are perhaps misleading as the longer-term carcinogenic potential is not seen in the relatively short life of birds.
- The long-term exposure risk of embedded shrapnel containing tungsten is a cause for concern. There is concern that there may be carcinogenic potential from some animal studies and case-control occupational studies in hard metal workers. The excess mortality from lung cancer in hard metal workers is a major concern.
Medical use of tungsten arterial embolisation coils
It has recently been noted that tungsten coils used in interventional radiology may be subject to degradation. This has implications for their ability to maintain arterial occlusion and any possible toxic effects due to dissemination of the material into patients' bodies. It appears, thus far, that there is very little risk of toxicity based on follow-up studies and in vitro analysis. However, patients have shown elevated blood tungsten levels and the long-term significance or possible effects of this are uncertain. The carcinogenic potential is of particular concern. It is not thought prudent to continue to use tungsten coils for this purpose.
- Suspect if there are symptoms of acute poisoning, as outlined above, in industrial workers or soldiers who may be exposed to tungsten.
- Inductively-coupled plasma-mass spectrometry (ICP-MS) may be used to detect and determine the concentration of tungsten in body fluids/tissues. The following is a guide:
- In cases of acute poisoning initial blood levels of 8 mg/L have been detected. In patients with degraded embolisation coils in situ, blood levels of 0.47-1.51 mg/L have been detected.
- Average blood levels in controls (those who had undergone aortic aneurysm grafting without coil embolisation) were 0.044 mg/L.
- The probable minimum lethal exposure range is 0.5-5 g/kg though there are few human data available.
- Get expert toxicological and ITU advice if tungsten poisoning is suspected.
- Treatment is mainly supportive.
- Charcoal may be given if it is not contra-indicated.
- In addition, oxygen should be given for respiratory symptoms.
- Benzodiazepines may be given for seizures.
- Haemodialysis has been used for renal failure and its sequelae, but with limited effect on tungsten clearance.
From the limited information available it appears that patients that survive an acute tungsten poisoning episode have a good chance of short- and long-term recovery if they receive appropriate supportive therapy and haemodialysis.
Further reading & references
- van der Voet GB, Todorov TI, Centeno JA, et al; Metals and health: a clinical toxicological perspective on tungsten and review of the literature. Mil Med. 2007 Sep;172(9):1002-5.
- Marquet P, Francois B, Vignon P, et al; A soldier who had seizures after drinking quarter of a litre of wine. Lancet. 1996 Oct 19;348(9034):1070.
- Marquet P, Francois B, Lotfi H, et al; Tungsten determination in biological fluids, hair and nails by plasma emission spectrometry in a case of severe acute intoxication in man. J Forensic Sci. 1997 May;42(3):527-30.
- Kraus T, Schramel P, Schaller KH, et al; Exposure assessment in the hard metal manufacturing industry with special regard to tungsten and its compounds. Occup Environ Med. 2001 Oct;58(10):631-4.
- Nemery B, Verbeken EK, Demedts M; Giant cell interstitial pneumonia (hard metal lung disease, cobalt lung). Semin Respir Crit Care Med. 2001 Aug;22(4):435-48.
- Barceloux DG; Cobalt. J Toxicol Clin Toxicol. 1999;37(2):201-6.
- Jordan CM, Whitman RD, Harbut M, et al; Neuropsychological sequelae of hard metal disease. Arch Clin Neuropsychol. 1993 Jul;8(4):309-26.
- Mitchell RR, Fitzgerald SD, Aulerich RJ, et al; Health effects following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards. J Wildl Dis. 2001 Jul;37(3):451-8.
- Kalinich JF, Emond CA, Dalton TK, et al; Embedded weapons-grade tungsten alloy shrapnel rapidly induces metastatic high-grade rhabdomyosarcomas in F344 rats. Environ Health Perspect. 2005 Jun;113(6):729-34.
- Moulin JJ, Wild P, Romazini S, et al; Lung cancer risk in hard-metal workers. Am J Epidemiol. 1998 Aug 1;148(3):241-8.
- Wild P, Perdrix A, Romazini S, et al; Lung cancer mortality in a site producing hard metals. Occup Environ Med. 2000 Aug;57(8):568-73.
- Peuster M, Fink C, von Schnakenburg C; Biocompatibility of corroding tungsten coils: in vitro assessment of degradation kinetics and cytotoxicity on human cells. Biomaterials. 2003 Oct;24(22):4057-61.
- Bachthaler M, Lenhart M, Paetzel C, et al; Corrosion of tungsten coils after peripheral vascular embolization therapy: influence on outcome and tungsten load. Catheter Cardiovasc Interv. 2004 Jul;62(3):380-4.
- Butler TJ, Jackson RW, Robson JY, et al; In vivo degradation of tungsten embolisation coils. Br J Radiol. 2000 Jun;73(870):601-3.
- Wester PO; Trace elements in serum and urine from hypertensive patients before and during treatment with chlorthalidone. Acta Med Scand. 1973 Dec;194(6):505-12.
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Dr Richard Draper
Dr Richard Draper