摘要：Objectives. We sought to identify predictors of lead concentrations in the blood, tibias, and patellae of older adults and to describe differences by gender, race/ethnicity, and other factors that can influence lead toxicokinetics and, thus modify health effects. Methods. Participants aged 50 to 70 years (N=1140) were randomly identified from selected neighborhoods in Baltimore, Maryland. We measured lead concentrations by anodic stripping voltammetry (in blood) and 109Cd-induced K-shell x-ray fluorescence (in bone). We used multiple linear regression to identify predictors of lead concentrations. Results. Mean (SD) lead concentrations in blood, tibias, and patellae were 3.5 (2.4) μg/dL, 18.9 (12.5) μg/g, and 6.8 (18.1) μg/g, respectively. Tibia concentrations were 29% higher in African Americans than in Whites ( P < .01). We observed effect modification by race/ethnicity on the association of gender and physical activity to blood lead concentrations and by gender on the association of age to tibia lead concentrations. Patella lead concentrations differed by gender; apolipoprotein E genotype modified this relation. Conclusions. African Americans evidenced a prominent disparity in lifetime lead dose. Women may be at higher risk of release of lead from bone and consequent health effects because of increased bone demineralization with aging. Lead was widely distributed in the environment from the beginning of the past century until it was removed from most commercial uses in the 1980s. 1 , 2 Because of lead’s widespread use, average blood lead concentrations among persons in the general population were estimated to be higher than 20 μg/dL in the 1960s 3 and 13 to 15 μg/dL in the late 1970s. 2 In blood, lead has a short clearance half-time of approximately 30 days but collects in bone; in the tibia, the clearance half-time is almost 3 decades. 4 Thus, past lead exposure can influence population health in several ways: through its persistence in the environment, persistent or progressive health effects from remote exposures, 5 or accumulation in, and later release from, bone in older adults who were alive during the period of peak population exposure. Currently, most American adults have low blood lead concentrations, 2 which represent integrated internal (release from bone) and external exposures over an average of the prior 120 days. However, older adults can have moderate to high bone lead concentrations. 6 Tibia lead, with its long clearance half-time, is an estimate of cumulative dose from past exposures. 6 The trabecular bone tissue in the patella is more biologically active and, with a clearance half-time of 3 to 5 years, is an estimate of the bioavailable bone lead pool. 7 , 8 Because the metabolism of lead in bone is similar to that of calcium, 9 bone lead can serve as an endogenous source of internal exposure, 10 – 12 particularly associated with accelerated demineralization in osteoporosis or aging, 11 , 13 – 15 resulting in subsequent risk of deposition in critical target organs. 16 To date, studies of bone lead concentrations have focused on populations in Boston, Massachusetts, or Mexico City, Mexico, with no diversity within studies by race/ethnicity, gender, or socioeconomic status (SES). 6 , 17 – 27 Although other studies have documented differences in blood lead concentrations by race/ethnicity and SES, 2 , 28 , 29 these studies did not simultaneously measure bone lead concentrations. No population-based studies have compared the bone lead concentrations of large numbers of African Americans and Whites, and no studies have included participants across the full spectrum of SES. Understanding differences in bone lead concentrations in blood, tibias, and patellae across sociodemographic groups may contribute to an explanation of persistent and widening health disparities. 28 , 30 – 32 This could lead to interventions to prevent or lessen the health risks associated with lead in late life. We examined lead concentrations and from our analysis determined predictors of blood, tibia, and patella lead concentrations in a population-based study of community-dwelling urban residents aged 50 to 70 years with diversity by gender, race/ethnicity, and SES.
