lead ( pb ) poisoning has numerous effects on the erythropoietic system , but the precise mechanism whereby high dose exposure causes anemia is not entirely clear . 
 we previously reported that pb exposure is associated with depressed serum erythropoietin ( epo ) in pregnant women residing in a pb mining town and in a nonexposed town in kosovo , yugoslavia . in a prospective study , 
 we tested the hypothesis that blood pb concentration ( bpb ) may be associated with depressed epo in children . 
 bpb , hemoglobin ( hgb ) , and serum epo were measured at ages 4.5 , 6.5 , and 9.5 years in 211 , 178 , and 234 children , respectively . at 4.5 years of age 
 , mean bpbs were 38.9 and 9.0 microg / dl in the exposed and nonexposed towns , respectively ; bpbs gradually declined to 28.2 and 6.5 microg / dl , respectively , by age 9.5 years . 
 no differences were found in hgb at any age . at age 4 . 
 5 years , a positive association between bpb and epo ( beta = 0.21 ; p = 0.0001 ) , controlled for hgb , was found . 
 the magnitude of this association declined to 0.11 at age 6.5 years ( p = 0.0103 ) and 0.03 at age 9.5 years ( p = 0.39 ) . 
 these results were confirmed using repeated measures analyses . 
 we concluded that in pb - exposed children , the maintenance of normal hgb requires hyperproduction of epo . with advancing age ( and continuing exposure ) 
 , this compensatory mechanism appears to be failing , suggesting a gradual loss of renal endocrine function due to pb exposure.imagesfigure 1figure 2