Environmental Exposure Of Thallium AndPotential Health Risk In An Area Of HighNatural Concentrations Of Thallium:Southwest Guizhou, China

Abstract

Little is known in literature about thallium (T1) exposure from naturally occurring T1 contamination. This paper draws attention to the potential health risk posed by high concentrations of naturally occurring T1 in the environment. The inhabitants of a rural area of Southwest Guizhou Province, China, reside within a natural T1 accumulated environment resulting from the Tl-rich sulfide mineralization, and they face a severe T1 exposure in their daily lives. High TI concentrations were detected in urines of the local residents. Measured urinary T1 levels are as high as to be 2.51-2,668 Ixg/L, surpassing the accepted world urine T1 level <1 mg/L for non-exposed humans. The urinary T1 levels show significant differences among 3 communities (n=21, p=0.001), but no significant difference in either sex or age groups (n=21, p=0.7806). However, there is a positive relationship between the extent of T1 exposure from T1 in soil and crops in the immediate environment and the levels of T1 detected in urine. This study has been able to identify that the elevated urinary T1 levels are mainly attributable to T1 accumulation in locally grown vegetables acquiring T1 from natural sources in local soils. It has also been possible to identify that the T1 in the urine of the local population represents a steady-state condition with long-term exposure, and the urinary excretion values can be taken as a biomarker of total dose based upon total daily dietary intake. This study indicates clearly high-concentration T1 of natural sources poses a potential health risk to the population, and that monitoring the urinary T1 level is a reliable and accurate way of bio-marking T1 exposure.