studies, one with male smelter workers (n = 57) in whom finger bone (mixed trabecular and cortical tissue) lead levels were measured (Osterberg et al. 1997). The second article describes the study of a sample of 54 storage battery workers in whom tibia and calcaneus lead levels were measured (Hanninen et al. 1998). This is the only study published to date to report an association between IBL and cognitive outcomes in which there was a lack of an association with bone lead levels. Both these studies used early XRF techniques (e.g., KXRF with cobalt-57) with higher limits of detection that have not been commonly used since, and this use makes the findings more difﬁcult to interpret. Bleecker et al. (1997), in Table 2. Continued. Author Stewart et al. 1999 Lucchini et al. 2000 Schwartz et al. 2000 Sample size (no.) 543 66 (E) 86 (NE) 535 (E) F/U = 99.8% with 1 + visit 118 (NE) F/U = 91.6% with 1 + visit Schwartz et al. 2001 803 (E) 135 (NE) Barth et al. 47 (E) 2002 53 (NE) XS XS L XS XS Percent male [mean age in Design years (SD)] 100 38% were ≥ 60 years of age (range, 40–70) Race/ ethnicity (%) White 92.8 100 (E) 40.1 (8.7) (NE) 42.6 (8.8) NR 100 55.6 (7.4) at ﬁrst visit (E) 58.6 (7.0) (NE) White 93.1 (E) 79.6 40.4 (10.1) (NE) 91.9 34.5 (9.1) Asian 100 100 39.5 (9.7) (E) 39.3 (8.4) (NE) NR Environmental Health Perspectives • VOLUME 115 | NUMBER 3 | March 2007 Blood lead, bone lead, and adult cognitive function a study similar to the one by Schwartz et al. (2001), reported stronger and more consis- tent associations of blood lead measures and neurobehavioral test performance compared to tibia lead levels. In the South Korean lead workers with current occupational exposure, a longitudinal analysis was performed to separate recent lead dose (measured as blood lead levels) from cumulative lead dose (measured as tibia lead levels), and acute effects from chronic effects in 575 subjects with complete data across the three study visits (Schwartz et al. 2005). The authors reported significant cross-sectional associations of blood lead levels with lower executive ability and manual dexterity test scores, with some evidence also for a longitu- dinal association of changes in blood lead lev- els with neurobehavioral decline. Tibia lead levels were more consistently associated with longitudinal declines in manual dexterity, executive abilities, neuropsychiatric symp- toms, and peripheral sensory functioning than change in blood lead levels. The authors con- cluded that lead was associated with worse cognitive function in two ways: an acute effect of recent dose and a chronic effect of cumulative dose. The authors also discussed that contrasting associations with blood and tibia lead levels could be due to the following: a) tibia and blood lead levels are biologically related and blood lead is in equilibrium with Source of Pb exposure Eastern U.S. tetraethyl and tetramethyl lead manu- facturing facility (U.S. Organolead Study) Primarily current/ past exposure Past Mean of 17.8 years since last exposure at time tibia lead obtained Lead accumulators Current and bullet 1–33 years manufacturers of exposure and 2 lead smelters in Northern Italy (E) Hospital (NE) Lead dose measure [mean (SD)] Tibia: 14.4 (9.3) Peak tibia: 23.7 (17.4) Blood: 27.5 (11.0) (E) 8.1 (4.5) (NE) IBLa: 409.8 (360.8) (E) TWAb: 31.7 (14.1) (E) Eastern U.S. Past Blood: 4.26 (2.6) (E) tetraethyl Mean of 16 Tibia: 14.4 (9.3) (E) and tetramethyl years since Peak tibia: 22.6 lead manu- exposure at (16.5) (E) facturing last baseline facility (E) Community-based random sampling from residential areas of former lead workers (NE) (U.S. Organolead Study) Battery, lead oxide Current Blood: 32 (15) (E) or car radiator (8 retired) 5.3 (1.8) (NE) manufacturing Tibia: 37.1 (40.3) (E) and secondary 5.8 (7.0) (NE) lead smelters (E) Air conditioner manufacturing or university (NE) (Korea Lead Study) Storage-battery Current Blood lead: plant (E) 0.1–36.1 30.8 (11.2) (E) Steel production years of 4.32 (2.0) NE) plant (NE) exposure (E) IBLh: 4,613.5 (Austria Lead (4,187.6) (E) Study) Covariates adjusted for outcome measures Summary of ﬁndings Age, race, education, Peak tibia lead strongest and most testing, lead measures, consistent predictor of test scores: years since last manual dexterity, executive ability, verbal exposure, depressive intelligence and memory score, tobacco, Current tibia lead also associated with alcohol consumption, same domains except verbal memory visit number On average, an increase in 22 µg/g peak Battery of tests— tibia lead was equivalent to an increase 8 domains in 5 years of age Age, education, alcohol, Neurologic symptoms smoking, coffee intake (neuropsychologic, sensory motor) more Neurological symptoms frequent, and decreased sensitivity to and a battery of 4 visual contrast sensitivity test in exposed neurobehavioral tests workers. These associations are with current blood lead and not cumulative lead measures (on a E vs. NE comparison, but not individual level) No differences between groups on neurobehavioral tests Signiﬁcant differences between low and high IBL groups on neuropsychologic scores Frequency matched on Exposed workers showed greater annual age, education and race declines than controls in verbal memory, Battery of tests— visuoconstruction domains 8 domains Peak tibia lead, but not blood lead, consistently predicted declines in test scores: symbol digit, verbal and visual memory, motor speed, and executive ability On average, an increase of 15.7 µg/g peak tibia lead was equivalent to annual test decline to ≥ 5 years of age at baseline Age, sex, education, each lead measure, height, BMI Battery of tests— 9 domains Blood lead was a better predictor of tests of executive abilities, manual dexterity, and peripheral motor strength than tibia or DMSA-chelatable lead On average, an increase of 5 µg/dL blood lead was equivalent to an increase of 1.05 years in age Age, years of education, Current blood lead levels, but not verbal intelligence, cumulative blood lead levels, were number of alcoholic correlated with executive functions and drinks per week/grams visuospatial abilities of alcohol per week Executive functioning and visuospatial Battery of tests— abilities differed signiﬁcantly between 5 domains exposed and control groups Continued, next page 487