Abstract
ObjectivesIt was considered that lead isotope ratios did not change during physical, chemical, or biological processes. Thus, lead isotope ratios have been used as fingerprints to identify possible lead sources. However, recent evidence has shown that the lead isotope ratios among different biological samples in human are not always identical from its lead origins in vitro. An animal experiment was conducted to explore the biological fractionation of lead isotopes in biological systems.Methods24 male Sprague-Dawley (SD) rats were divided into groups that received acute lead exposure (0, 0.02, 0.2, or 2 mg/kg body weight of lead acetate) via the respiratory route every day for 5 days. Biological samples (i.e., blood, urine, and feces) were collected for comparison with the lead acetate (test substance) and the low-lead animal feed (diet) administered to the rats. The lead isotope ratios were determined by inductively coupled plasma mass spectrometry (ICP-MS).ResultsThere are significant differences (p<0.05) in lead isotope ratios between blood, urine, and feces. Moreover, a nonlinear relationship between the blood lead concentration and the blood lead isotope ratios was observed. There is also a threshold effect to the fractionation function. Only the blood isotope ratio of 204Pb/206Pb matches the test substance well. As for feces, when 204Pb/206Pb ratio is considered, there is no significant difference between feces-test substance pairs in medium and high dose group.ConclusionsThe biological fractionation of lead isotopes in SD rats was observed. Moreover, there might be a threshold for the biological fractionation of lead isotopes which is depending on whole blood lead level. It is considered to be more reliable that we compared the isotope ratios of potential lead hazards with both blood and feces lead fingerprints especially for 204Pb/206Pb ratio under high-dose exposure.
Highlights
Historical long problem of public exposure to lead is still a significant global public health concern due to its cumulative toxicity [1]
The lead isotope ratios were determined by inductively coupled plasma mass spectrometry (ICPMS)
There might be a threshold for the biological fractionation of lead isotopes which is depending on whole blood lead level
Summary
Historical long problem of public exposure to lead is still a significant global public health concern due to its cumulative toxicity [1]. As Cheng and Hu [5] reported that lead undergoes a minimal mass-dependant isotope fractionation in natural physical, chemical, and biological processes due to its large atomic weight. These natural variations in lead isotope ratios can be used to determine the origins of lead. Lead isotope analysis is the most effective method for the provenance study of lead pollutants This technique is commonly used to identify human lead exposure sources in various disciplines, including agriculture, archaeology, and environmental science [6,7,8]
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