Study on the biological exposure limit of whole blood chromium in occupational hexavalent chromium compounds exposed population
Objective To analyze the exposure-response relationship of peripheral whole blood chromium level and lung function as well as genetic toxicity indicators in workers exposed to hexavalent chromium[Cr(Ⅵ)]compounds,and to propose a biological exposure limit of whole blood chromium for soluble Cr(Ⅵ)compounds-exposed workers.Methods A total of 515 workers from a dynamic occupational Cr(Ⅵ)compounds-exposed cohort in an enterprise from 2010 to 2017 were selected as the research subjects using a retrospective cohort study.A total of 918 followed-up results of research subjects and baseline data of a cohort were analyzed based on bibliometric analysis.The results include lung function tests,whole blood chromium level detected by inductively coupled plasma-mass spectrometry,urinary 8-hydroxy-2'-deoxyguanosine(8-OHdG)detected by high performance liquid chromatography-tandem mass spectrometry,peripheral micronuclei frequency(MNF)detected by cytokinesis-block micronucleus assay,and mitochondrial DNA copy number(mtCN)detected by real-time fluorescence quantitative polymerase chain reaction.Results The results of bibliometric analysis showed that domestic and foreign studies on biological monitoring of Cr(Ⅵ)compounds increased year by year in the past 30 years,and whole blood chromium levels had a good correlation with the occupational Cr(Ⅵ)compounds exposure.The geometric mean of whole blood chromium levels in males and females among the occupational Cr(Ⅵ)compounds exposure cohort was 2.77 and 1.79 μg/L,respectively.A turning point appeared in 6.00 μg/L chromium in whole blood of the exposure-response curve of whole blood chromium levels with lung function indicators and genetic toxicity indicators.For each unit increase in the natural logarithm-transformed whole blood chromium level,the forced expiratory volume in one second(FEV1)decreased by 0.05 L,the FEV1/forced-vital-capacity decreased by 0.67％,the peak expiratory flow decreased by 0.15 Us,the maximal mid-expiratory flow decreased by 0.09 Us,the MNF increased by 0.149‰,the urinary 8-OHdG increased by 0.090 μg/g,and the mtCN increased by 0.013.When the whole blood chromium level was＞6.00 μg/L,there was a significant increase in urinary 8-OHdG,MNF,and mtCN(all P＜0.01).Conclusion The level of whole blood chromium can be used as a biomarker for occupational exposure to soluble Cr(Ⅵ)compounds.The preliminary biological exposure limit is set at 6.00 μg/L for whole blood chromium in workers exposed to soluble Cr(Ⅵ)compounds.
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