UKPID MONOGRAPH TELLURIUM WN Harrison PhD CChem MRSC SM Bradberry BSc MB MRCP JA Vale MD FRCP FRCPE FRCPG FFOM National Poisons Information Service (Birmingham Centre), West Midlands Poisons Unit, City Hospital NHS Trust, Dudley Road, Birmingham B18 7QH This monograph has been produced by staff of a National Poisons Information Service Centre in the United Kingdom. The work was commissioned and funded by the UK Departments of Health, and was designed as a source of detailed information for use by poisons information centres. Peer review group: Directors of the UK National Poisons Information Service. TELLURIUM Toxbase summary Type of product Tellurium and its compounds are industrial chemicals used in metal alloys, "daylight lamps" and the electronics industry. Toxicity Acute poisoning is rare. Two men died after 2g sodium tellurite was mistakenly injected during retrograde pyelography (Keall et al, 1946). Exposure may occur occupationally, particularly during the production of metal alloys and electrolytic copper refining. Features Topical - Irritant to skin and eyes. - May cause dermal discolouration. Inhalation - A garlic odour to the breath, sweat and urine is characteristic of tellurium exposure. - A metallic taste, nausea, loss of appetite, tiredness, reduced sweating and unspecified ECG changes have been reported. - May cause respiratory tract irritation, although reports of significant pulmonary toxicity are rare. Ingestion - A garlic odour of the breath, sweat, urine and faeces is characteristic of tellurium exposure. - Initial symptoms of nausea, vomiting and a metallic taste develop within hours. - Fever, hair loss, weight loss and fatigue may occur days to weeks after substantial ingestion. Injection - A garlic odour of the breath and body secretions is characteristic after systemic administration of tellurium. - Loin pain, nausea, vomiting, confusion, dyspnoea and cyanosis occurred in two patients following accidental intraureteric injection of 2g sodium tellurite; both died (Keall et al, 1946). Management Dermal 1. If possible the patient should remove soiled clothing and wash him/herself. 2. Wash contaminated hair and skin with soap and copious amounts of water. 3. Pay special attention to skin folds, fingernails and ears. Ocular 1. Immediately irrigate the affected eye thoroughly with tepid water or 0.9% saline for at least 10-15 minutes. 2. Any particles lodged in the conjunctival recesses should be removed. 3. Continue irrigation with saline infusion using drip tubing. 4. Repeated instillation of local anaesthetic may reduce discomfort and help more thorough decontamination. 5. Corneal damage may be detected by instillation of fluorescein. 6. Patients with corneal damage and those whose symptoms do not resolve rapidly should be referred for ophthalmological assessment. Ingestion Minor ingestions (very mild or no symptoms): 1. Gastrointestinal decontamination is unnecessary. 2. Symptomatic and supportive measures only. Moderate/substantial ingestions: 1. Gastric lavage should be considered only if the patient presents within one hour; its value is unproven. 2. Symptomatic and supportive measures as dictated by the patient's condition. 3. Monitor the ECG, biochemical and haematological profiles. 4. Collect urine and blood for tellurium concentration measurements to confirm diagnosis although these assays are not widely available. Check with NPIS. 5. It has been suggested that ascorbic acid may reduce the garlic odour from tellurium intoxication (De Meio, 1947) but this has not been confirmed. 6. Dimercaprol increases tellurium toxicity and should not be used. Inhalation 1. Remove from exposure 2. Treat symptomatically and supportively. 3. If symptoms occur perform a chest X-ray, ECG, biochemical and haematological profiles. 4. Collect urine and blood for tellurium concentration measurements to confirm diagnosis although these assays are not widely available. Check with NPIS. 5. It has been suggested that ascorbic acid may reduce the garlic odour from tellurium intoxication (De Meio, 1947) but this has not been confirmed. 6. Dimercaprol increases tellurium toxicity and should not be used. Injection 1. Symptomatic and supportive care as dictated by the patients condition. 2. Monitor the ECG, biochemical and haematological profiles. 3. Collect urine and blood for tellurium concentration measurements to confirm diagnosis although these assays are not widely available. Check with NPIS. 4. It has been suggested that ascorbic acid may reduce the garlic odour from tellurium intoxication (De Meio, 1947) but this has not been confirmed. 5. Dimercaprol increases tellurium toxicity and should not be used. REFERENCES Blackadder ES, Manderson WG. Occupational absorption of tellurium: a report of two cases. Br J Ind Med 1975; 32: 59-61. De Meio RH. Tellurium. II. Effect of ascorbic acid on the tellurium breath. J Ind Hyg Toxicol 1947; 29: 393-5. Keall JHH, Martin NH, Tunbridge RE. A report of three cases of accidental poisoning by sodium tellurite. Br J Ind Med 1946; 3: 175-6. Kron T, Hansen C, Werner E. Renal excretion of tellurium after peroral administration of tellurium in different forms to healthy human volunteers. J Trace Elem Electrolytes Health Dis 1991; 5: 239-44. Müller R, Zschiesche W, Steffen HM, Schaller KH. Tellurium-intoxication. Klin Wochenschr 1989; 67: 1152-5. Substance name Tellurium Origin of substance Usually found naturally as the telluride of gold (calverite). It is produced as a by-product of the smelting of copper and other metals. (Gerhardsson et al, 1986) Synonyms Aurum paradoxum Metalum problematum (DOSE, 1994) Chemical group A group VIA element Reference numbers CAS 13494-80-9 (DOSE, 1994) RTECS WY 2625000 (RTECS, 1997) UN 3284 (HAZARD TEXT, 1997) HAZCHEM CODE NIF Physicochemical properties Chemical structure Te (DOSE, 1994) Molecular weight 127.60 (DOSE, 1994) Physical state at room temperature Crystalline solid or amorphous powder. (Gerhardsson et al, 1986) Colour Crystals are silvery white, powder is black. (Gerhardsson et al, 1986) Odour Odourless (HSDB, 1997) Viscosity NIF pH NIF Solubility Elemental tellurium is insoluble in water. (Gerhardsson et al, 1986) Autoignition temperature NIF Chemical interactions Tellurium is not attacked by hydrochloric acid. It reacts with nitric acid and with concentrated or fuming sulphuric acid. In the presence of air, it dissolves in potassium hydroxide with formation of a deep-red solution. (HSDB, 1997) Major products of combustion Tellurium dioxide. (HSDB, 1997) Explosive limits NIF Flammability Burns slowly in air. (HSDB, 1997) Boiling point 990°C. (DOSE, 1994) Density 6.2 (Gerhardsson et al, 1986) Vapour pressure 133.3 Pa at 520°C (DOSE, 1994) Relative vapour density NIF Flash point NIF Reactivity A finely divided suspension of elemental tellurium in air can be exploded. The fire hazard of tellurium is moderate in the form of dust when exposed to heat or flame or by chemical reaction with oxidizing agents. Reactions with zinc, chlorine, fluorine, and solid sodium are vigorous and have a potential to cause fires (HSDB, 1997). Uses Additive to metal alloys. Vulcanization of rubber. Semiconductors and electronic devices. Catalyst. Tellurium vapour is used in "daylight lamps". Used in blast caps. Limited use in pottery glazes. (PATTY, 1993) Hazard/Risk Classification NIF INTRODUCTION Tellurium has the appearance and physical properties of a metal yet has the chemical properties of a non-metal. It forms compounds in oxidation states -2, +2, +4 and +6. Of toxicological interest are elemental tellurium, tellurium dioxide, the gases hydrogen telluride and tellurium hexafluoride, and the water soluble salts of tellurous and telluric acid. It also forms a number of organometallic complexes (Gerhardsson et al, 1986). There is no evidence that tellurium is an essential trace element. Tellurium exposure is characterized by a distinctive garlic odour which is due to formation of the hepatic metabolite dimethyl telluride. EPIDEMIOLOGY Tellurium is used as an additive in many metallurgical processes such that it is often involved in multiple metal exposures, notably with lead, zinc, arsenic, selenium, cadmium and thallium. Tellurium exposure also occurs during electrolytic copper refining where tellurium is formed in the anode slime. Tellurium intoxication is rare, though acute (Gerhardsson et al, 1986; Blackadder and Manderson, 1975) and chronic (Keall et al, 1946; Shie and Deeds, 1920) occupational exposure has been reported. An isolated case of poisoning from tellurium-contaminated meat has been reported (Müller et al, 1989). The source of contamination is unknown. The only reported deaths from tellurium intoxication occurred when two men were mistakenly injected with some 2 g sodium tellurite during retrograde pyelography (Keall et al, 1946). MECHANISMS OF TOXICITY There are few data on the mechanism of toxicity of tellurium or its compounds. Animal studies suggest tellurium may affect the conversion of squalene to cholesterol so interfering with neurotransmission via demyelination (Gerhardsson et al, 1986). Impaired secretory nerve neurotransmission is the proposed mechanism of impaired saliva and sweat secretion in humans and of reduced gastric acid secretion in animals poisoned with tellurium (Shie and Deeds, 1920). There is some evidence that the aroma of fresh garlic is caused by a high tellurium content. This may contribute to garlic's cholesterol- lowering properties (Larner, 1995). In vitro studies demonstrate that tellurite (Te4+) ions can penetrate the erythrocyte membrane and, in the presence of reduced glutathione, form telluride (Te2+) which causes irreversible membrane damage and hence haemolysis (De Meio and O'Leary, 1975; Kurantsin- Mills et al, 1988). Tellurate (Te6+) ions do not penetrate the erythrocyte membrane. Haemolysis has been observed in animals poisoned with tellurium (Shie and Deeds, 1920), but not as a feature of tellurium intoxication in man. TOXICOKINETICS Absorption The mean (± SD) gastrointestinal absorption in healthy volunteers ingesting between 15 and 57 µg has been estimated as ten per cent (± 4 per cent) for elemental tellurium, 23 per cent (± 9 per cent) for tellurate and 21.5 per cent (no SD given) for tellurite (Kron et al, 1991). Ingestion of 0.5 µg tellurium oxide produced a garlic breath odour within 75 minutes which lasted for 30 hours (Reisert, 1884). Tellurium dusts and fumes can be absorbed via the lung. Workers exposed to tellurium concentrations up to 0.1 mg/m3 had urine tellurium concentrations of up to 0.06 mg/L (Steinberg et al, 1942). Organometallic complexes of tellurium and soluble tellurium salts can be absorbed through the skin (Blackadder and Manderson, 1975). Distribution Tellurium is distributed widely with high concentrations particularly in kidneys, liver, bone, brain and testes (Meditext, 1997). Excretion Excretion is mainly renal although small amounts of tellurium are exhaled as dimethyl telluride which has a distinctive garlic odour which may persist for many days; Reisert (1884) reported garlic breath odour for 237 days following ingestion of 15 mg tellurium oxide. The susceptibility to this effect varies considerably between individuals and is exacerbated by alcohol consumption (Cerwenka and Cooper, 1961). The whole body retention time of tetravalent tellurium has been estimated as more than two months (Kron et al, 1991). CLINICAL FEATURES: ACUTE EXPOSURE Dermal exposure Although it has been claimed that some tellurium compounds give rise to skin burns or rashes following dermal contact (Gerhardsson et al, 1986), no original case data were cited in support. Blue-black patches in the webs of the fingers and streaks on the neck were observed in two postgraduate chemists who handled volatile tellurium esters. The discolouration was believed to be due to deposition of elemental tellurium in the dermis and subcutaneous tissue (Blackadder and Manderson, 1975). Ocular exposure Some tellurium compounds are irritant although there are no reports of ocular exposure to tellurium or its compounds producing adverse effects. Exposure to either hydrogen telluride or to shampoo containing tellurium oxide has not caused eye problems (Grant and Schuman, 1993). Inhalation Reports from the Russian literature state that tellurium dust or fumes and hydrogen telluride are irritant to the respiratory tract (Gerhardsson et al, 1986). No pulmonary features were reported when two postgraduate chemists were exposed to some 50 g tellurium hexafluoride gas which leaked from a cylinder into a small laboratory. The first individual developed a metallic taste, anorexia and tiredness and, after two days, an erythematous papular vesicular rash on the hands, arms and neck. This was diagnosed as contact dermatitis, possibly from wearing rubber gloves, although the ability of tellurium to inhibit sweating may have contributed. The second person affected experienced only a metallic taste and somnolence. Both patients developed a garlic odour to the breath, sweat and urine which persisted for several weeks (Blackadder and Manderson, 1975). Haematological and biochemical profiles and chest X-ray were normal. Three workers exposed to tellurium fumes for ten minutes developed a garlic breath odour and experienced a metallic taste, headache and "epigastric distress" within 24 hours. Twenty-four hour urine tellurium concentrations in collections commenced some 48 hours post exposure varied between 7.7 µg/L and 12.0 µg/L. The full blood count in each case showed a mild lymphocytosis (40-51 per cent of the total white cells). All recovered fully without treatment but were given an eight day course of dimercaprol in an attempt to clear the garlic odour, which disappeared one to four days after cessation of treatment (Amdur, 1947). No tellurium was detectable in the urine 17 days after presentation. Two cases of occupational exposure to tellurium vapour have been reported in the Russian literature (Gerhardsson et al, 1986). Features included a garlic breath odour with general weakness, pallor, cough, shivering, fever, sinus tachycardia, amnesia and black-green discolouration of the mucosa of the tongue and the nasopharynx. Ingestion A 37 year-old woman developed characteristic symptoms of tellurium exposure "only hours" after eating a small piece of meat containing 800-1000 µg/kg tellurium of unknown origin. Initially she experienced nausea, vomiting, a metallic taste and a garlic odour of the breath, sweat, urine and faeces. The next day she developed a fever which resolved over some five days as the gastrointestinal features subsided. The patient noticed hair loss two weeks after intoxication and was referred to hospital after four weeks with weight loss, fatigue and a persistent garlic breath odour. Examination was normal except for the strong garlic odour. Gastroscopy showed petechial bleeding in the gastric fundus. Serum and urine tellurium concentrations were 27.6 µg/L (normal = 1.0 µg/L) and 3.1-3.2 µg/L (normal = 1.0 µg/L) respectively. The patient was given ascorbic acid 200 mg per day and discharged. Hair loss ceased eight weeks after intoxication with a "bright colour" to new grown hair. The garlic odour persisted for some ten months, intensifying after alcohol intake. No persistent health effects were reported. (Müller et al, 1989). Injection Three patients were accidentally poisoned when sodium tellurite was administered instead of sodium iodide during retrograde pyelography (Keall et al, 1946). Two of these patients who each received an estimated 2 g tellurite died. A garlic odour was observed around the first patient, a 40 year old male, some 90 minutes after sodium tellurite was injected into the left ureter. After a further 75 minutes the patient complained of severe discomfort in the left loin and subsequently vomited. Four hours after the procedure he became deeply cyanosed and dyspnoeic and died twenty minutes later (Keall et al, 1946). The second patient, a 31 year old male, developed a garlic odour within an hour of undergoing pyelography. He became confused and progressively cyanosed with only partial relief from oxygen therapy. Spectroscopy of the patient's blood revealed an abnormal pigment which was not methaemoglobin and could not be identified. The patient died six hours after sodium tellurite injection (Keall et al, 1946). At autopsy both patients showed marked cyanosis of the head and neck. An intense yellow colour was observed in body fat and a deep brown colour in muscles. Black deposits were found in the mucosa of the bladder and in the injected ureter. Congestion was noted in the lungs, liver, spleen and kidneys with marked fatty degeneration and oedema in the liver. A garlic odour was emitted from all tissues (Keall et al, 1946). The third patient, a 21 year old male, received a smaller (unknown) dose of sodium tellurite due to a blocked catheter. After four days a garlic odour was noticed and the patient became slightly cyanosed, complained of a "nasty taste" in the mouth and was administered intravenous fluids. He vomited the following day but recovered fully by day seven. The garlic odour disappeared after 12 days (Keall et al, 1946). CLINICAL FEATURES: CHRONIC EXPOSURE Exposure to tellurium compounds is most likely to occur in the form of dusts and fumes in industry. Only hydrogen telluride, tellurium dioxide and potassium tellurite are of occupational significance (Glover, 1983). No deaths or permanent health effects have been reported following exposure. Inhalation Thirteen individuals working near the blast furnaces in a lead refinery were examined for signs of tellurium exposure (Shie and Deeds, 1920). The workers were believed to have been exposed to hydrogen telluride though no exposure data were given. Seven had a garlic odour to the breath, sweat and urine, and dryness and a metallic taste in the mouth. Five had "considerable inhibition of the sweat function" and three developed dry and itchy skin, anorexia, nausea, vomiting, depression and somnolence. A survey of ninety-eight workers exposed to 0.01-0.1 mg/m3 tellurium for 22 months revealed similar effects. The most common findings were a garlic odour of the breath (84 individuals), dryness of the mouth (32), a metallic taste (27) and garlic odour of the sweat (20). Other symptoms included somnolence (16), loss of appetite (9) and nausea (3). No evidence of sweat suppression was found. Urinalysis revealed increased tellurium concentrations (0.01 to greater than 0.06 mg/L) in the exposed group compared to controls. Symptoms occurred even in those with urine tellurium concentrations less than 0.01 mg/L, though the frequency increased at higher tellurium concentrations with somnolence and a garlic sweat odour occurring only in workers with a urine tellurium concentration greater than 0.01 mg/L (Steinberg et al, 1942). MANAGEMENT Dermal exposure If possible the patient should remove any contaminated clothing him/herself. Affected areas of skin should be washed with copious quantities of water. Pay special attention to skin folds, fingernails and ears. Burns should be treated conventionally as for thermal burns (e.g. silver sulphadiazine dressing). Ocular exposure Irrigate immediately with lukewarm water or preferably saline for at least 10-15 minutes. Specialist ophthalmological advice should be sought if any abnormality is detected or suspected on examination and in those whose symptoms do not resolved rapidly. Inhalation Immediate management involves removal from exposure, establishment of a clear airway and administration of supplemental oxygen if necessary. Mechanical ventilation may be required. Other symptomatic and supportive measures should be dictated by the patients condition. Ingestion Gastric lavage may be considered if presentation is within the first hour, though there are no clinical data regarding its value. It is not known whether activated charcoal will adsorb tellurium. Symptomatic and supportive measures should be employed. An ECG should be performed and biochemical and haematological profiles undertaken. Blood and urine tellurium concentrations are not widely available but may be of interest retrospectively to confirm systemic uptake. Injection The management of a patient following injection of tellurium is symptomatic and supportive as dictated by the patient's condition. Monitoring and investigations are as for tellurium ingestion. Antidotes Animal studies Four guinea pigs were administered 5 mg intramuscular dimercaprol eight hours prior to the intramuscular injection of 75 mg tellurium oxide. A second group of four similarly poisoned guinea pigs received dimercaprol eight hours after tellurium oxide injection. Both groups then received dimercaprol 5 mg tds for 24 hours and 5 mg bd for a further 24 hours. There was 100 per cent mortality in the two dimercaprol administered groups (n=8) within 48 hours (and all animals showed pronounced haematuria) whereas the 48 hour survival rate in control animals (n=4) administered tellurium oxide alone was 75 per cent. A single guinea pig administered only intramuscular dimercaprol 5 mg every eight hours for 24 hours remained healthy. The weights of the animals were not stated (Armdur, 1958). Clinical studies Three men exposed to tellurium fumes developed a strong garlic breath odour and were treated with 2.5 mg/kg dimercaprol intramuscularly every four hours for 24 hours, every six hours for a further 24 hours and then daily for six days. Each patient reported accentuation of the garlic odour following the injection and the odour disappeared one to four days after the cessation of treatment. There was no evidence of enhanced tellurium elimination with therapy (Amdur, 1947). Ascorbic acid Animal studies The reduction in garlic odour from rabbits and guinea pigs intoxicated with tellurium following administration of ascorbic acid (route not described) has been reported. The proposed mechanism is reduction of ionized to elemental tellurium with decreased dimethyl telluride formation (De Meio, 1947). Intramuscular ascorbic acid 25 mg tds for 24 hours then 25 mg bd for a further 24 hours did not increase the one week survival of guinea pigs injected intramuscularly with 75 mg tellurium oxide compared to controls (Amdur, 1958). Clinical studies Workers exposed to tellurium dust were treated with 8-10 mg/kg ascorbic acid (route not stated) one to three times daily. A reduction in the garlic odour of the breath was noted which recurred on cessation of treatment (De Meio, 1947). A 37 year old woman who ingested an unknown amount of tellurium was treated with ascorbic acid 200 mg daily (route not stated). She recovered fully though a garlic odour of the breath persisted from some ten months (Müller et al, 1989). Antidotes: Conclusions and recommendations 1. Animal studies suggest dimercaprol increases tellurium toxicity and, as there is no evidence that it enhances tellurium elimination, it should not be employed. 2. Ascorbic acid may decrease the extent of garlic odour in persons with tellurium intoxication although this has not been confirmed in controlled studies. MEDICAL SURVEILLANCE The most obvious indication of tellurium exposure is a garlic odour to the breath, which occurs in association with urine tellurium concentrations greater than 1 µg/L (Gerhardsson et al, 1986). This clinical indication of tellurium exposure may be masked in those with badly smelling breath (i.e. bronchiectasis, grossly carious teeth, severe gingivitis) (Gerhardsson et al, 1986). Normal concentrations in biological fluids The "upper normal limits" for tellurium in non-occupationally exposed individuals have been reported as 1.0 µg/L in serum and 1.0 µg/L in urine (Müller et al, 1989). OCCUPATIONAL DATA Occupational exposure standard Tellurium and compounds, except hydrogen telluride. Long-term exposure limit 0.1 µg/m3 (as Te) (Health and Safety Executive, 1997). OTHER TOXICOLOGICAL DATA Carcinogenicity There are no reports associating tellurium or its compounds with the development of cancer in humans. Reprotoxicity There are no reports of exposure to tellurium or its compounds causing reproductive effects in humans although pregnant rats fed diets containing 500 to 3500 ppm tellurium gave birth to hydrocephalic (non- obstructive) offspring, the incidence of hydrocephalus being proportional to the tellurium dose (Duckett, 1970). The mechanism of this effect is not known. Genotoxicity An increase in the incidence of chromosome breakage was found when in vitro human leukocytes were treated for 48 hours with 1.2 x 10-8 mol/L sodium tellurite and 2.4 x 10-7 mol/L ammonium tellurite (Paton and Allison, 1972). Fish toxicity NIF EC Directive on Drinking Water Quality 80/778/EEC NIF WHO Guidelines for Drinking Water Quality NIF AUTHORS WN Harrison PhD CChem MRSC SM Bradberry BSc MB MRCP JA Vale MD FRCP FRCPE FRCPG FFOM National Poisons Information Service (Birmingham Centre), West Midlands Poisons Unit, City Hospital NHS Trust, Dudley Road, Birmingham B18 7QH UK This monograph was produced by the staff of the Birmingham Centre of the National Poisons Information Service in the United Kingdom. The work was commissioned and funded by the UK Departments of Health, and was designed as a source of detailed information for use by poisons information centres. Date of last revision 28/1/98 REFERENCES Amdur ML. Tellurium. Accidental exposure and treatment with BAL in oil. Occup Med 1947; 3: 386-91. Amdur ML. Tellurium oxide: an animal study in acute toxicity. Arch Ind Health 1958; 17: 665-7. Blackadder ES, Manderson WG. Occupational absorption of tellurium: a report of two cases. 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Steinberg HH, Massari SC, Miner AC, Rink R. Industrial exposure to tellurium: atmosphere studies and clinical evaluation. J Ind Hyg Toxicol 1942; 24: 183-92.