Uptake of inhaled lead from motor exhaust

Chamberlain, A. C.; Clough, W.S.; Heard, M.J.; Newton, D.; Stott, A. N. B.; Wells, A. C.

doi:10.1136/pgmj.51.601.790

Cited by 23 publications

(10 citation statements)

References 10 publications

(13 reference statements)

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“…Another important factor affecting gastrointestinal absorption is the relative condition of the gut, that is, whether in a fasted or non-fasted state. Radioactive and stable isotope tracer studies have shown that the absence of Ca and other minerals in the gastrointestinal tract at the time of Pb ingestion is a major reason for increased Pb absorption in fasting subjects compared with nonfasting subjects ( Blake and Mann 1983 ; Chamberlain et al 1978 ; Heard and Chamberlain 1982 ; Rabinowitz et al 1976 , 1980 ). When Ca and other minerals are present, however, differences between fasting and nonfasting subjects are not significant ( Heard and Chamberlain 1982 ; Krebs et al 1997 ; Rabinowitz et al 1980 ).…”

Section: Discussionmentioning

confidence: 99%

Low Blood Lead Levels Do Not Appear to Be Further Reduced by Dietary Supplements

Gulson

Mizon

Korsch

et al. 2006

Environ Health Perspect

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ObjectiveOur objective was to evaluate the association of dietary intakes of selected micronutrients and blood lead (PbB) concentrations in female adults and in children.DesignWith longitudinal monitoring, we measured daily intakes of the micronutrients calcium, magnesium, sodium, potassium, barium, strontium, phosphorus, zinc, iron (limited data), and copper from 6-day duplicate diets (2–13 collections per individual) and PbB concentrations. Participants were three groups of females of child-bearing age (one cohort consisting of 21 pregnant subjects and 15 nonpregnant controls, a second cohort of nine pregnant migrants), and one group of 10 children 6–11 years of age.ResultsMean PbB concentrations were < 5 μg/dL. A mixed linear model that included only group and time accounted for 5.9% of the variance of the PbB measurements; neither the effect of time nor the effect of group was significant. The model containing all of the micronutrients (except iron, for which there was a great deal of missing data), along with time and group, accounted for approximately 9.2% of the variance of PbB; this increase was not statistically significant. There was, however, a significant association of PbB with phosphorus, magnesium, and copper when all micronutrients were included in the statistical analysis, perhaps reflecting a synergistic effect.ConclusionsIn contrast to most previous studies, we found no statistically significant relationships between the PbB concentrations and micronutrient intake. In adults and older children with low PbB concentrations and minimal exposure to Pb, micronutrient supplementation is probably unnecessary.

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Section: Discussionmentioning

confidence: 99%

Low Blood Lead Levels Do Not Appear to Be Further Reduced by Dietary Supplements

Gulson

Mizon

Korsch

et al. 2006

Environ Health Perspect

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“…Animals were exposed to Pb acetate or test material for 15 days, with the dose for each day being administered in two equal portions given at 0900 hr and 1500 hr (2 hr before feeding). We selected these exposure times so that Pb ingestion would occur at a time when the stomach was largely or entirely empty of food, because the presence of food in the stomach is known to reduce Pb absorption (e.g., Blake et al 1983 ; Chamberlain et al 1978 ; Heard and Chamberlain 1982 ; James et al 1985 ; Rabinowitz et al 1980 ).…”

Section: Methodsmentioning

confidence: 99%

Estimation of Relative Bioavailability of Lead in Soil and Soil-Like MaterialsUsing Young Swine

Casteel

Weis

Henningsen³

et al. 2006

Environ Health Perspect

170

157

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In this article we summarize the results of a series of studies that measured the relative bioavailability (RBA) of lead in a variety of soil and soil-like test materials. Reference material (Pb acetate) or Pb-contaminated soils were administered orally to juvenile swine twice a day for 15 days. Blood samples were collected from each animal at multiple times during the course of the study, and samples of liver, kidney, and bone were collected at sacrifice. All samples were analyzed for Pb. We estimated the RBA of a test material by fitting mathematical models to the dose–response curves for each measurement end point and finding the ratio of doses that gave equal responses. The final RBA for a test material is the simple average of the four end point–specific RBA values. Results from 19 different test materials reveal a wide range of RBA values across different exposure materials, ranging from 6 to 105%. This variability in RBA between different samples highlights the importance of reliable RBA data to help improve risk assessments for Pb in soil. Although the RBA value for a sample depends on the relative amounts of the different chemical and physical forms of Pb present, data are not yet adequate to allow reliable quantitative predictions of RBA from chemical speciation data alone.

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“…In these studies, exposures were to particles having mass median aerodynamic diameters below 1 m and, therefore, deposition of the inhaled lead particles can be assumed to have been primarily in the bronchiolar and alveolar regions of the respiratory tract (James et al, 1994 ) where transport of deposited lead to the gastrointestinal tract is likely to have been only a minor component of particle clearance ( Hursh et al, 1969 ). The ICRP lead model includes four deposition compartments from which a total of 95% of deposited lead is absorbed with half -times ranging from 1 h to 2 days, and 5% is transferred to the stomach (Chamberlain et al, 1978 ). The slowest respiratory tract compartment would be expected to have the largest impact on blood lead concentrations resulting from acute inhalation exposures.…”

Section: Discussionmentioning

confidence: 99%

“…Since lead absorbed into the systemic circulation would be expected to have similar biokinetics, regardless of the route of absorption, the concern resides in how well the model simulates deposition and absorption of lead in the respiratory tract. The respiratory tract portion of the ICRP model is empirically based on experimental observations from inhalation studies conducted in adults, which revealed multicompartmental absorption kinetics for deposited lead (Hursh and Mercer, 1970;Hursh et al, 1969;Wells et al, 1975;Chamberlain et al, 1978;Morrow et al, 1980 ). In these studies, exposures were to particles having mass median aerodynamic diameters below 1 m and, therefore, deposition of the inhaled lead particles can be assumed to have been primarily in the bronchiolar and alveolar regions of the respiratory tract (James et al, 1994 ) where transport of deposited lead to the gastrointestinal tract is likely to have been only a minor component of particle clearance ( Hursh et al, 1969 ).…”

Section: Discussionmentioning

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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Uptake of inhaled lead from motor exhaust

Cited by 23 publications

References 10 publications

Low Blood Lead Levels Do Not Appear to Be Further Reduced by Dietary Supplements

Low Blood Lead Levels Do Not Appear to Be Further Reduced by Dietary Supplements

Estimation of Relative Bioavailability of Lead in Soil and Soil-Like MaterialsUsing Young Swine

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†

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