| BackgroundArsenic is a poisonous metal-like element in environmental chemistry. It exists widely in the soil, underground water, sea water and food. Endemic arsenic poisoning induced by high levels arsenic in drinking water is the main endemia in our country. Furthermore, occupational arsenic poisoning is also one of the occupational diseases in our country. Arsenic poisoning can injure many organs in the body, including kidney. Many researchers around the world are exploring the biomarkers of renal injury induced by arsenic exposure. Urinary arsenic is usually thought to be the main biomarker of arsenic exposure. Levels of P2 microglobulin and activities of N-acetyl-β-D-glucosaminidase (NAG) and y-Glutamy-transferase (y-GT) in the urine are commonly used as the biomarkers of renal injury. Benchmark dose (BMD) was defined by Crump in 1984. The BMDS was mainly used for risk assessment of low-level exposure of toxicant. There are similar situation between the BMD and the critical concentration, and both of them are calculated based on a dose-response relationship, therefore it is feasibility to use the BMDS to estimate the PCC of a general population exposure to arsenic. A suitable Benchmark dose limit (BMDL) is often defined as the 95% lower confidence limit estimate of dose corresponding to a 10% level of risk above background. The purpose of this study is to explore the renal dysfunction and the arsenic exposure limit in workers exposed to arsenic occupationally by using the method of BMD.Methods173 workers in the coppery smelting plant were selected as the subjects of exposure group, and 62 workers in the machining plant of the same factory were selected as the subjects of control group. Data of worker's illness, life style and history of harmful material exposure were obtained through questionnaire. Workers with renal disease were excluded in the investigation. All subjects in the study were asked to fast seafood for 3 days before examination. Urinary samples of all subjects were collected in the morning. Levels of arsenic in the urine is determined by using hydride generation-atomic fluorescence spectrometry; levels ofβ2-MG were measured by RIA assay; activities of NAG andγ-GT in the urine were assayed by velocity method using automatic biochemical analyzer.ResultsMean levels of urinary arsenic in the subjects of exposure group were 140.33μg/L, varied among 19.42 to 451.60μg/L, and which in control group is 35.60μg/L, varied among 8.90 to 89.00μg/L. The group difference was significant (P<0.01).Levels ofβ2-MG and activities of NAG andγ-GT in the urine of subjects from exposure group were significantly higher than those in control group (P<0.01).Levels ofβ2-MG and activities of NAG andγ-GT in the urine of subjects from exposure group correlated positively and significantly with levels of urinary arsenic.Dose-response relationship was used to estimate BMD and BMDL of different parameters about renal dysfunction. The estimated BMD and BMDL of arsenic levels in the urine were 132.65μg/L and 107.73μg/L forγ-GT,123.87μg/L and 99.76μg/L forβ2-MG,114.72μg/L and 92.22μg/L for NAG.ConclusionResults of this study suggested that 114.72μg/L arsenic in the urine was the limit of renal dysfunction induced by arsenic exposure, and 92.22μg/L was the limit of arsenic exposure.
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