Effects of occupational lead exposure on bone mineral density and bone metabolism in workers

Objective To investigate the effects of occupational lead exposure on the bone mineral density and the bone metabohsm in exposed workers.Methods Two hundred and ninety-eight lead-exposed workers in a storage battery plant in Shanghai were selected as the exposed subjects while eighty-one healthy officers in the plant who were not occupationally exposed to lead were treated as the control.The blood lead (BPb) and the urinary lead(UPb)were used as the exposure biomarkers while the Z score,the urinary hydrox- yproline(HYP),the serum alkaline phosphatase(ALP),the serum alkaline phosphatase(bone isoenzyme) (BALP) and the serum osteocalcin(BGP) were used as the effect biomarkers for the bone effect caused by the lead.Bone mineral density(BMD)was measured by the monophoton absorptiometry(SPA-4).Results The BPb,UPb,HYP,ALP,BALP in the occupational lead exposure group were higher than those in the control group with significantly statistical difference in male(P0.01).The levels of BGP in the exposure group was higher than that in the control group without significantly statistical difference (P0.05).The BMD in the expo- sure group was lower than that in the control group without significantly statistical difference(P0.05). The BMD was significantly decreased in the groups of the UPb 10～μg/g Cr level compared with the 0～μg/g Cr group with the significant difference(P0.01).In males,the BMD was significantly decreased in the group of the BPb 300-μg/L level compared with the 0～μg/L group with the significant difference (P0.01).The levels of HYP,ALP,BALP,BGP in the UPb 20～μg/g Cr group were significantly higher than those in the UPb 0～μg/g Cr group (P0.05).The levels of HYP,ALP,BALP,BGP in the BPb 300～μg/L group were significantly higher than those in the BPb 0～μg/L group (P0.05).The prevalence of both osteoporosis and the abnormal bone metabolisms indexes would increase significantly with the increase of the lead exposure(P0.01)with the linear correlation (P0.01).But the prevalence of higher BGP had no significant correlation with UPb (P0.05). BMDs were calculated using BMDS Version 1.3.2 software and BMDLs were also determined.The BMDLs of BPb and UPb for lead-induced osteoporosis were higher than those representing the change of bone metabolism induced by lead.Conclusions The occupational exposure to lead could cause the decrease of the bone miner- al density,lead to the osteoporosis,and may affect the bone metabolism.