OBJECTIVE: To evaluate the possibility of cumulative blood lead and blood ZPP as surrogates of lead body burden and to investigate their association with renal function as an index of lead body burden. METHODS The study subjects comprised 678 lead workers with past blood lead and blood ZPP data from their employment. Cumulative blood and ZPP were calculated by accumulating the every year mean value of both indices from the new employment since 1983. To assess the cumulative data of lead workers who started their lead work before 1983, the years before 1983 were simulated with the first available data from 1983. Study variables for lead body burden were tibia bone lead and DMSA chelatable lead, whereas those for current lead biomarkers were blood lead and blood ZPP. BUN and serum creatinine were selected as clinical renal biomarkers, while NAG (N-acetyl-D-glucosamine) and RBP (Retinol binding protein) were selected as early renal biomarkers. RESULTS The association between cumulative blood lead and blood ZPP with tibia bone lead was statistically significant with determinant coefficients (r(2)) of 0.72 and 0.567, respectively, and their relationships were better explained by the curvilinear regression model. In multiple regression analysis of current lead biomarkers on the renal biomarkers after controlling for possible confounders (age, sex, job duration, smoking and drinking status), blood lead was associated only with log-transformed NAG, whereas blood ZPP was associated with 3 other renal biomarkers. On the other hand, in multiple regression analysis of biomarkers of lead body burden on renal biomarkers after controlling for possible confounders (age, sex, job duration, smoking and drinking status), cumulative blood ZPP and tibia bone lead were associated with all 4 renal function biomarkers, whereas cumulative blood lead and DMSA chelatable lead were associated with 3 renal biomarkers except BUN. CONCLUSION Cumulative blood and ZPP were demonstrated to be good surrogates of lead burden. Furthermore, the cumulative blood ZPP was confirmed to have a better association than the cumulative blood lead.
In order to investigate the level of lead absorption of lead workers and to evaluate the effect of blood lead on blood zinc protoporphyrin (ZPP) and prevalence of lead related symptoms, 1,782 lead workers(male: 1,506, female: 276) from 8 storage battery industries were studied. Selected variables as indices of lead exposure were blood lead, blood ZPP, and hemoglobin (HB). Fifteen questionnaires of lead related symptoms were provided to all lead workers and filled up by themselves and confirmed by medical doctors. Personal variables such as age, work duration, smoking and drinking habits were also collected. The results were follows : 1. While the mean blood lead of lead workers of all lead companies was 31.0+/-3.0 ug/100ml (male: 31.5+/-2.9 ug/100ml, female: 27.9+/-3.3 ug/100m1), the mean blood ZPP of all lead workers was 66.7+/-4.1 ug/100ml (male: 59.6+/-3.3, female: 105.3+/-3.0 ug/100ml). The mean hemoglobin of male lead workers was 15.7+/-.3 gm/100ml and that of female lead workers was 13.0+/-.3 gm/100ml. 2. The percentage of lead workers whose blood lead was over 60.0 ug/100m1 and 40.0-59.9 ug/100ml was 2.81 % and 19.08 %, respectively. On the other hand, the percentage of lead workers whose blood ZPP was over 150 ug/100ml and 100-149 ug/100ml was 5.89 % and 8.31 %, respectively. 3. The slopes of simple linear regression of blood lead (independent variable) and blood ZPP in female lead workers was significantly steeper than that of male lead workers. The slope of storage battery industries with better working condition in terms of low air concentration of lead were less steeper than those with poor working condition with high mean air concentration of lead. 4. Stepwise multiple regression analysis, using overall symptom prevalence as a dependent variables, blood lead, blood ZPP, hemoglobin, age, work duration, drinking and smoking habits as independent variables, indicated that only drinking habit and age were significantly contributed to the dependent variable.
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