A Noninvasive Isotopic Approach to Estimate the Bone Lead Contribution to Blood in Children: Implications for Assessing the Efficacy of Lead Abatement

Abstract

Lead hazard control measures to reduce children’s exposure to household lead sources often result in only limited reductions in blood lead levels. This may be due to incomplete remediation of lead sources and/or to the remobilization of lead stores from bone, which may act as an endogenous lead source that buffers reductions in blood lead levels. Here we present a noninvasive isotopic approach to estimate the magnitude of the bone lead contribution to blood in children following household lead remediation. In this approach, lead isotopic ratios of a child’s blood and 5-day fecal samples are determined before and after a household intervention aimed at reducing the child’s lead intake. The bone lead contribution to blood is estimated from a system of mass balance equations of lead concentrations and isotopic compositions in blood at the different times of sample collection. The utility of this method is illustrated with three cases of children with blood lead levels in the range of 18–29 μg/dL. In all three cases, the release of lead from bone supported a substantial fraction of the measured blood lead level postintervention, up to 96% in one case. In general, the lead isotopic compositions of feces matched or were within the range of the lead isotopic compositions of the household dusts with lead loadings exceeding U.S. Environmental Protection Agency action levels. This isotopic agreement underscores the utility of lead isotopic measurements of feces to identify household sources of lead exposure. Results from this limited number of cases support the hypothesis that the release of bone lead into blood may substantially buffer the decrease in blood lead levels expected from the reduction in lead intake.

Blood lead levels and cumulative blood lead index (CBLI) as predictors of late neurodevelopment in lead poisoned children

“…Therefore, lead in bone can elevate blood lead levels even when external lead exposure ceases. This endogenous exposure (Brito et al , 2002; Gwiazda et al , 2005; Fleming et al , 1997) would be expected to have the same health effects as external lead exposure. There have been technological limitations to bone lead measurements which limited the ability to measure lead in the less dense bones of children.…”

Lead poisoning and the deceptive recovery of the critically endangered California condor

“…Sample Processing and Analysis. To determine lead concentrations and isotopic compositions, whole-blood, feather, ammunition/fragment, and paint samples were processed and analyzed using established trace metal clean techniques (22,31,44,45). ALAD activity in condor whole-blood samples was measured using a colorimetric assay based on previously described methods (46,47) (SI Materials and Methods).…”

Medical Toxicology Case Presentations: to Chelate or Not to Chelate, Is that the Question?

“…Some have argued that similar treatment strategies should be applied to adults as are currently recommended for children [6]. In particular, one of the symposium presenters, Dr. Donald Smith, noted that much of the recrudescent blood lead (even in children) comes from bone mobilization [7]. This makes the decision to chelate a given BLL even more problematic in view of redistributing lead from bone versus reducing brain exposure to lead [4,5].…”