Application Of Benchmark Dose Method On Dose-responserelationship Between Occupational Exposure To Lead And Biological Effects

[Objective] A retrospective cohort survey was conducted in a lead and zinc smelting company, and the dose-response relationships of the cumulative exposure dose with lead poisoning, and abnormalities of blood lead, urine lead, blood zinc porphyrin and other relevant indicators of lead workers were studied in order to prove reference for the revision of lead exposure standards.[Methods] Workers exposed to lead from January1,1988to December31,2008in the company were selected for the subjects. The Occupational medical data and the monitoring data of air lead in the workshop over the years were collected. The lead content in the samples were determined by graphite furnace atomic absorption spectrometry or dithizone method, blood serum zinc protoporphyrin by the fluorescence method and urinary fecal porphyrin by UV-fluorescence determination. All data were analyzed using SPSS statistical software, and the BMD Version2.2.1software was used to calculate the benchmark dose (BMD) and BMD of the lower95%confidence interval (BMDL), and calculate the benchmark dose of air lead concentrations for controling lead poisoning and the abnormalities blood lead, urine lead and blood zinc porphyrin.[Results] It is indicated in the correlation analysis that there are positive correlation between the cumulative lead exposuredose and blood lead, urine lead or blood zinc porphyrin, followed by its associated blood lead level> urine lead> Blood zinc porphyrin, and positive correlation between urinary lead, blood lead and blood zinc porphyrin, closely followed by blood lead level-blood zinc porphyrin> blood lead-lead in urine> serum zinc porphyrin-lead in urine. The incidence of lead poisoning, abnormal rates of blood lead and urine lead and blood zinc porphyrin increased with an increase of cumulative lead dust (smoke) exposure, there are dose-response relationships and these are significantly (p<0.001) by the trend chi-square test, BMDL values of Lead poisoning, blood zinc porphyrin, blood lead and urine lead in the lead dust exposure group were0.0228mg/m3,0.0434mg/m3,0.0580mg/m3and0.0017mg/m3, the BMDL values of Lead poisoning, blood zinc porphyrin, blood lead in lead smoke exposed group were0.0100mg/m3,0.0174mg/m3and0.0148mg/m3. BMDL of Lead poisoning is0.0228mg/m3(dust),0.0100mg/m3(smoke), are slightly lower compared with current occupational health standards (TWA)) in China.[Conclusion] The results suggest that the cumulative exposure dose is a better indicator for lead exposure, BMDL values controlling lead poisoning are0.0228mg/M3(lead dust) and0.0100mg/M3(lead smoke), suggesting that workers are exposed to. lead under the existing national health standards may still result in lead poisoning. It is appropriate that benchmark dose method is used in the study of dose-response relationship between the accumulative exposure and biological effects of the population to accumulative chemicals, the results can be used as an important basis to develop occupational exposure limits for chemicals.