Thallium cement production

It is not possible to make a global risk assessment of the ecotoxicological importance of these emissions, mainly because very few investigations and observations have been carried out. The phytoavailability of thallium from contaminated soils decreased rapidly after application (Martin and Kaplan 1998). More detailed results have been reported on the thallium flow in cement production, whereupon thallium is introduced into the process via the stone (limestone, clay) and ore raw materials. 

Thallium — Metal (atomic weight 204.383 gmol-1) found in nature mostly associated with minerals of copper, zinc, lead, and iron. Industrial production is based on electrolytic reduction from solutions of thallium in sulfuric acid obtained by dissolution of dust and cementation residues generated during lead and zinc production. 

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. 

Thallium is obtained commercially from flue dust residues of zinc and lead smelters, and occasionally as a byproduct in cadmium production. Approximately 12 tons are produced worldwide each year for commercial use [9]. Approximately 1600 tons of thallium is released annually from emission sources such as refineries, coal-burning power plants, metal smelters, and cement plants [3]. Thallium is also released into the environment in runoff from copper and zinc mines. 

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