基准剂量在苯致血液毒性职业接触限值的应用

目的探讨苯职业累积接触造成的血液毒性效应,建立苯接触的损伤效应的剂量-反应关系,并估算苯致血液毒性的基准剂量值。方法选择安徽某汽车制造厂涂装车间苯作业工人为苯接触组936人,对照组216人,在职业体检时检测外周血象、血压,并询问自觉症状;利用Proast 38.9软件计算基准剂量(BMD),推算基准剂量的95%低限水平(BMDL)。结果对照组白细胞数值为(5.73±1.08)×10^9/L,接触组数值为(5.33±1.33)×10^9/L,差异有统计学意义(P<0.01);苯累积接触量与白细胞计数之间存在剂量-反应关系,得到BMD的值为18.76 mg/m^3/年,基准剂量下限值是10.70 mg/m^3/年。将工作年限按40年计,苯的时间加权平均阈限值应为0.268 mg/m^3。结论苯作为确定的致癌物质,苯累积接触量与作业工人白细胞之间存在相互关联,职业接触限值的研究有助于推动以保护职业有害物质接触人群为目标的职业安全制度的修订。

Application of Benchmark Dose(BMD)in occupational exposure limit of benzene-induced hematotoxicity

Objective To investigate the dose-effect relationship between cumulative exposure dose(CED)of benzene and hematotoxicity,thereby to estimate its benchmark dose(BMD).Methods Hemogram assay was used in 936 benzene-exposed workers and 216 controls for the detection of hematotoxicity in peripheral blood.The cumulative exposure dose(CED)of benzene was calculated based on the job type and duration of each worker and benzene concentration in workplaces.Dose-response relationship between CED of benzene and white blood cell was evaluated for the calculation of BMD.Results The results showed that the white blood cell count in exposure group was(5.33±1.33)×10^9/L,significantly lower than that of control group(5.73±1.08)×10^9/L(P<0.01),the 95%lower confidence bound of BMD of CED was 10.70 mg/m^3 per year for both genders;if assume the work life was 40 years,the estimated exposure limit should be 0.286 mg/m^3 per year.Conclusions Benzene exposure may induce hematotoxicity even at the occupational exposure levels below the occupational health standard of China.Therefore,better dose-response assessment and BMD estimation are demanded in order to improve the quantification of occupational exposure limits of benzene and to protect against cancer risk.