Occupational exposure thallium

Hair has been used in the biomonitoring of various elements, for example, arsenic, thallium, and zinc, and has been used in the monitoring of drugs and biological substances. The level of mercury in hair is widely used as a biological indicator for exposure to methyl mercury (MeHg). In addition, hair samples have been utilized to evaluate environmental exposure to pollutants such as lead, and occupational exposures to metals such as nickel and chromium. However, the ATSDR has stated ... 

Besides accidential or suicidal ingestion, there is occupational exposure of some groups of employees in the production and processing of heavy metal ores, manufacturing and use of thallium, its alloys and compounds, and in certain cement factories from roasting pyrites and ingestion of dust from the electric filter (Schaller et al., 1980). Whereas the excretion level in urine from persons without known occupational contact with thallium was found to be lower than 1.1 mg Tl/kg creatinine, it significantly increases upon exposure. No influence of the age of the person examined and the duration of employment, as well as no influence of alcohol and nicotine consumption was noted. 

The thallium content in hair from persons without environmental or occupational exposure is 5-15 ng/g hair [9,14]. The thallium content in tissue from unexposed humans is highest in colon, kidney, and myocardium. The reported values, however, for all tissues are less than 10 ppb and often below 1 ppb [9,10,17,18]. Cellular distribution studies using nontoxic doses of Tl demonstrated high levels of thallium in the nucleus and showed that 10% of total intracellular thallium accumulated in the mitochondria [10,19]. 

Alopecia from thallium is no longer an occupational problem. Cases of accidental discoloration of hair (copper, cobalt, and silver) and nails (mercury, lead, silver and chromium) by occupational exposure are nowadays rarely seen at outpatient clinics. Green hair from copper exposure is mainly non-occupational. 

Dolgner R, Brockhaus A Ewers U, et al Repeated surveillance of exposure to thallium in a population living in the vicinity of a cement plant emitting dust containing thallium. IntArch Occup Environ Health 52 69-94, 1983... 

TABLE 11-1. Occupational settings at risk for thallium exposure... 

The National Institute for Occupational Safety and Health (NIOSH) has recommended that 15 mg/m of thallium be considered immediately dangerous to life and health. This is the exposure level of a chemical that is likely to cause permanent health problems or death. 

Residents near thallium-emitting cement plants had elevated urine thallium concentrations up to 100-fold higher than unexposed persons [57]. Urinary thallium values for nearby residents actually exceeded those found in workers at the plants. The presumed route of exposure was ingestion of home-grown vegetables. Some of the thallium urine concentrations approached values clinically considered to be toxic (>50p.g/liter) [58] but no definite cases of toxicity were documented [11,57]. An increased incidence of headaches and sleeplessness was noted. An occupational study of 128 workers at these cement plants revealed no evidence of clinical toxicity [12]. Another study of workers manufacturing thallium-based alloys also found no clinical effects [59]. Oil refinery workers who had elevated levels of urine thallium (10-23 p.g/day) were noted to have a mild alopecia areata [60]. A report exists of ill-defined functional changes in the nervous systems of workers exposed to thallium carbonate in the USSR [61]. 

In summary, there is no definitive evidence of thallium-induced teratogenic or genotoxic effects in humans with either acute high-dose or chronic low-dose exposure. Transplacental thallium intoxication, however, can occur following acute maternal ingestion of the toxin. Occupational or environmental exposure, with rare exception, does not result in clinical toxicity [22],... 

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