Baseline Level of Blood Lead Concentration Among Japanese Farmers

Lead concentrations were determined for more than 2500 blood samples (more than 2000 winter samples and approximately 500 summer samples) collected from farmers in various parts of Japan to establish reliable baselines for blood lead levels; the analysis was conducted in a single laboratory to avoid any inter-laboratory errors. Blood lead levels distributed log-normally with a geometric mean (i.e., a geometric standard deviation) of 48.6 micrograms/L (1.51) for males and 32.1 micrograms/L (1.50) for females. The levels observed were among the lowest in the industrialized countries of the world. The sex difference was significant (P less than .01) while the difference in Pb-B between winter and summer was essentially insignificant. Both drinking and smoking habits were associated with a dose-dependent increase in blood lead levels, especially in males; the increment was additive when the examinee was a drinker-smoker. The geographical difference in blood lead levels remained inconclusive.