Sir,
Exposure to thallium (Tl: Atomic weight of 204.38 and atomic number of 81) and lead (Pb: 207.21 and 82) are important global health-ill problem in particular in developing world.[1,2] These elements are derived from two sources anthropogenic or geogenic.[2] To date, the later has been underestimated in health.
It is shown that geogenic thallium and lead are associated with mineralization of hydrothermal and pyrite mineral, and coal deposits.[3] Thallium is generally present in very low concentrations in soils generally range from 0.01 to 3 mg/kg.[4] These concentrations are not properly established; however, most soils contain thallium at concentrations of <1 mg/kg.[3]
Concentration of Lead in natural soil is varied from 2 to 200 mg/kg (average 10) mg/kg.[5] We have previously reported anthropogenic thallium and lead exposure and toxicities from Iran due to occupational environments, food sources and even adulterated opioid abuse.[6,7]
There is geological potential of thallium and lead in Chelpu area. There are many diseases in this area that could be associated with the presence of these two toxic elements. Therefore, we evaluated thallium and lead in soil in Chelpu area that could potentially contribute in toxic exposure. 26 soil samples were collected from Chelpu catchment area, North east Iran. Soil samples were passed through a 120 mesh sieve and crushed. The samples were then analyzed for thallium and lead levels using ICP-ES via Iranian Geological Organization, Tehran.
Mean (SD, min-max) thallium and lead concentrations in soil were 3.64 (0.88, 2.2-5.4) and 12.13 (7.57, 0.6-26.5), respectively, (n = 26). These values are comparable with international reports [Table 1].
Table 1.
Thallium and lead concentrations in soil samples of Chelpu in comparison to baseline values of natural soils
We found that thallium concentration in Chelpu soil samples was higher than natural soils reported from other geographical regions including International, Chinese and Canadian guidelines.[3,8,9] Lead concentration in Chelpu soil samples was also higher than natural soils in world but lower than natural Chinese soils and Canadian guidelines.[3,5,9] There have been some attempts to establish guidance for preventive measures related to lead pollution and toxicity in Iran. Physicians should be aware of potential consequences related to chronic thallium and lead toxicities in some regions. Sporadic refractory lead toxicities could also be associated with geogenic exposure. Further studies are needed to determine the extent of health impact of geogenic thallium and lead exposures in the area.
AUTHOR'S CONTRIBUTIONS
MT contributed in the conception of the work, design of the work, analysis and interpretation of data, revising the draft, approval of the final version of the manuscript, and agreed for all aspects of the work. JM contributed in the conception of the work, design of the work, conducting the study, revising the draft, approval of the final version of the manuscript, and agreed for all aspects of the work. RA contributed in the conception of the work, conducting the study, interpretation of the data, revising the draft, approval of the final version of the manuscript, and agreed for all aspects of the work. MHMG contributed in the conception of the work, analysis and interpretation of data, revising the draft, approval of the final version of the manuscript, and agreed for all aspects of the work.
ACKNOWLEDGMENTS
This study has been supported by a grant from Ferdowsi University of Mashhad for MSc thesis (M.T. first author) in cooperation with Mashhad University of Medical Sciences, Mashhad, Iran.
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