The ICRP age-specific biokinetic model for lead: validations, empirical comparisons, and explorations.

Pounds, Joel G.; Leggett, R. W.

doi:10.1289/ehp.98106s61505

Cited by 33 publications

(23 citation statements)

References 23 publications

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“…The question of how the bone mineral bioapatite-a calcium phosphate-takes up and releases these elements has launched a lively debate among numerous research groups. Health physicists have long debated in vivo remodeling (biologically controlled resorption and reprecipitation of bioapatite) vs. volume diffusion for explaining the slowest rates of uptake and release (3)(4)(5)(6)(7)(8); such research is commonly termed biokinetics. Geochemists debate in vitro recrystallization and surface adsorption vs. diffusion for explaining trace element profiles in fossils, although diffusive processes are normally assumed (9,10).…”

mentioning

confidence: 99%

Trace element diffusivities in bone rule out simple diffusive uptake during fossilization but explain in vivo uptake and release

Kohn

Moses

2012

Proc. Natl. Acad. Sci. U.S.A.

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Diffusion rates of numerous trace elements in bone at 20°C were determined using laser-ablation inductively coupled plasma mass spectrometry analysis of experimentally induced diffusion profiles. Diffusivities are about 1 order of magnitude slower than current semiquantitative geochemical views and about 1.5 orders of magnitude faster than indirect radiotracer estimates. Intrabone volume diffusion is too slow and too similar among many elements to explain trace element profiles in young fossils and archeological materials. Diffusivity differences among elements do, however, explain disparate biokinetic washout of Sr vs. Ba and of light vs. heavy rare earth elements (REEs). These results improve the understanding of the physical principles underlying biokinetic models and rates and mechanisms of trace element alteration of phosphatic tissues in paleontological, archeological, and crystal-chemical contexts. Recrystallization and transport limitations in soils explain trace element profiles in young fossils better than intrabone volume diffusion alone and imply that diffusion of REE and other trivalent cations is likely controlled by a common charge-compensating species rather than ionic radii or partition coefficients.T race elements can pose major health risks, especially radioactive products of nuclear processes. Many of these elements concentrate in bone (bone-seeking elements), including P, Ca, Zn, Sr, Ba, lanthanides, Pb, and actinides, where they can reside for decades before being gradually eliminated from the body (1). Bone's tenacious affinity for certain trace elements persists postmortem, as evidenced by orders of magnitude higher concentrations of trace elements in archeological bones and fossils compared with modern tissues (2). The question of how the bone mineral bioapatite-a calcium phosphate-takes up and releases these elements has launched a lively debate among numerous research groups. Health physicists have long debated in vivo remodeling (biologically controlled resorption and reprecipitation of bioapatite) vs. volume diffusion for explaining the slowest rates of uptake and release (3-8); such research is commonly termed biokinetics. Geochemists debate in vitro recrystallization and surface adsorption vs. diffusion for explaining trace element profiles in fossils, although diffusive processes are normally assumed (9, 10). Diffusion underpins both types of research because it provides a strict lower limit for rates of trace element uptake and release both in vivo and in vitro. Understanding diffusion rates therefore improves predictions of long-term clearance of trace elements from the body, as well as geological or archeological interpretations of trace elements or their isotopes, such as U-series geochronology, conditions of deposition and fossilization, and forensic discrimination among fossils (2).Surprisingly, virtually no experiments constrain trace element diffusion rates in bone, and we can find no studies that measured diffusion profiles directly. Consequently, we conducted 18-mo exper...

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confidence: 99%

Trace element diffusivities in bone rule out simple diffusive uptake during fossilization but explain in vivo uptake and release

Kohn

Moses

2012

Proc. Natl. Acad. Sci. U.S.A.

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“…However, comparisons made between the ICRP and IEUBK models have shown that the ICRP model tends to predict higher quasi -steady state blood lead concentrations than the IEUBK model for the same rates of lead absorption ( Pounds and Leggett, 1998 ). Thus, predicted blood lead concentrations and corresponding risk estimates (e.g., P 10 ) for long -term exposures that are based on the ICRP model can be expected to be higher than those based on the IEUBK model.…”

Section: Discussionmentioning

confidence: 99%

“…Potential impacts of air lead exposures at the RSR site on blood lead concentrations in young children were assessed using the EPA IEUBK model ( v.99d) and the International Commission of Radiologic Protection ( ICRP ) lead model (Leggett, 1993;Pounds and Leggett, 1998). Although there are many differences between the two models, one difference particularly relevant to this analysis is the exposure time step ( the shortest time interval over which the exposure can be varied in a simulation ).…”

Section: Introductionmentioning

confidence: 99%

Risks to children from exposure to lead in air during remedial or removal activities at Superfund sites: A case study of the RSR lead smelter Superfund site†

Khoury

Diamond

2003

J Expo Sci Environ Epidemiol

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Superfund sites that are contaminated with lead and undergoing remedial action generate lead -enriched dust that can be released into the air. Activities that can emit lead -enriched dust include demolition of lead smelter buildings, stacks, and baghouses; on -site traffic of heavy construction vehicles; and excavation of soil. Typically, air monitoring stations are placed around the perimeter of a site of an ongoing remediation to monitor air lead concentrations that might result from site emissions. The National Ambient Air Quality ( NAAQ ) standard, established in 1978 to be a quarterly average of 1.5 g / m 3 , is often used as a trigger level for corrective action to reduce emissions. This study explored modeling approaches for assessing potential risks to children from air lead emissions from the RSR Superfund site in West Dallas, TX, during demolition and removal of a smelter facility. The EPA Integrated Exposure Uptake Biokinetic ( IEUBK ) model and the International Commission of Radiologic Protection ( ICRP ) lead model were used to simulate blood lead concentrations in children, based on monitored air lead concentrations. Although air lead concentrations at monitoring stations located in the downwind community intermittently exceeded the NAAQ standard, both models indicated that exposures to children in the community areas did not pose a significant long -term or acute risk. Long -term risk was defined as greater than 5% probability of a child having a long -term blood lead concentration that exceeded 10 g / dl, which is the CDC and the EPA blood lead concern level. Short -term or acute risk was defined as greater than 5% probability of a child having a blood lead concentration on any given day that exceeded 20 g / dl, which is the CDC trigger level for medical evaluation ( this is not intended to imply that 20 g / dl is a threshold for health effects in children exposed acutely to airborne lead ). The estimated potential long -term and short -term exposures at the downwind West Dallas community did not result in more than 5% of children exceeding the target blood lead levels. The models were also used to estimate air lead levels for short -term and long -term exposures that would not exceed specified levels of risk ( risk -based concentrations, RBCs ). RBCs were derived for various daily exposure durations ( 3 or 8 h / day ) and frequencies ( 1 -7 days / week ). RBCs based on the ICRP model ranged from 0.3 ( 7 days / week, 8 h / day ) to 4.4 g / m 3 ( 1 day / week, 3 h / day ) for long -term exposures and were lower than those based on the IEUBK model. For short -term exposures, the RBCs ranged from 3.5 to 29.0 g / m 3 . Recontamination of remediated residential yards from deposition of air lead emitted during remedial activities at the RSR Superfund site was also examined. The predicted increase in soil concentration due to lead deposition at the monitoring station, which represented the community at large, was 3.0 mg / kg. This potential increase in soil lead concentration was insignificant, less th...

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“…It was presented and discussed at the workshop at which this paper was also presented (28). The Leggett/ICRP model is an expansion of an ICRP age-specific model of lead metabolism (17,18 [year]-dependent intake rates and applies an age-dependent fractional absorption to them), the forms of the two curves for uptake of lead from food and water cannot be made congruent (Figure 14) Figure 15).…”

Section: Comparison With the Leggett/icrp Modelmentioning

confidence: 99%

A physiologically based kinetic model for lead in children and adults.

O’Flaherty

1998

Environ Health Perspect

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The ICRP age-specific biokinetic model for lead: validations, empirical comparisons, and explorations.

Cited by 33 publications

References 23 publications

Trace element diffusivities in bone rule out simple diffusive uptake during fossilization but explain in vivo uptake and release

Trace element diffusivities in bone rule out simple diffusive uptake during fossilization but explain in vivo uptake and release

Risks to children from exposure to lead in air during remedial or removal activities at Superfund sites: A case study of the RSR lead smelter Superfund site†

A physiologically based kinetic model for lead in children and adults.

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