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PubMed1990

Assessing the contribution from lead in mining wastes to blood lead.

Lead has been recognized for years as an environmental pollutant of concern for young children. Nonetheless, many children in the United States still experience high body burdens of lead. Reducing exposure to lead must include an assessment of all potential sources of lead and a definition of routes of exposure. In this paper, the relationships between soil lead and blood lead concentrations in residents in communities with high soil lead concentrations resulting from past mining and ore processing (milling) activities are compared to those derived from studies in urban communities or communities with operating smelters. The impact of mine waste-derived lead in soil (usually in the form of lead sulfide) on blood lead is less than that for lead in soil derived from smelter, vehicle, or paint sources. Possible reasons for a reduced impact of lead sulfide on blood lead in children in mining communities include the following: lead from mining sources contributes less to lead in the immediate environment of children than lead from other sources; mine wastes typically are of larger particle size, which decreases the bioavailability of lead in the gastrointestinal tract; and lead sulfide is absorbed less in the gastrointestinal tract compared to other lead species. A reduced impact of mine waste-derived lead on blood lead may be important from a regulatory point of view. Expensive cleanup actions for lead-contaminated soils in mining communities based on acceptable soil lead concentrations derived from smelter or urban communities may be questionable in terms of reducing blood lead in children.

Humans↗
PubMed1997

[Low-level lead exposure and children's intelligence from recent epidemiological studies in the U.S.A. and other countries to progress in reducing lead exposure and screening in the U.S.A].

From the 1980s many well-designed epidemiological studies have confirmed that low-level, subclinical lead exposure in early life is associated with decrements in children's intelligence. Neurodevelopmental deficits from exposure to a low level of lead have been held to be not only an American problem, but also a worldwide issue in the past decade. Good epidemiological studies were reported from England, Scotland, Germany, Greece, Australia and New Zealand. Well-designed cross-sectional and prospective studies were carried out to quantify the magnitude of the relation between full scale IQ in children aged five years or more and the burden of lead (PbB or PbT) in early life of children. Of five cross-sectional studies of blood lead, two demonstrated a significant inverse association between lead and IQ even after adjustment for confounders. Two other studies, however, showed no firm evidence of inverse association after adjustment for confounders, and the remaining study demonstrated no significant inverse association of five cross-sectional studies of tooth lead, two indicated an inverse association between tooth lead and IQ, two others showed no significant inverse association after adjustment for confounders, and the remaining one manifested no association. Of four prospective studies, two revealed strong evidence of an inverse association between blood lead at the age of around two years and IQ. Another one, however, revealed an inverse association between mean postnatal blood level and IQ, while the remaining one demonstrated no significant inverse association between IQ and postnatal blood lead level after adjustment for confounders. In a comprehensive review of 26 epidemiological studies since 1979, including a meta-analysis, Pococok et al. indicated that doubling of the body lead burden (from 10 to 20 micrograms/dl) blood lead or (from 5 to 10 micrograms/g) tooth lead is typically associated with a mean deficit in full-scale IQ of around 1-2 IQ points. Lead in interior household dust, exterior surface soil, and old residential lead paint, which is deteriorated or removed, constitute the major sources of lead poisoning in children in the United States. Infants and children, who typically engage in hand to mouth activities, frequently come into contact with lead dust in soil and on the floor. Marked declines both in air lead and blood lead concentrations are evident parallel to the phase-down of lead in gasoline and soldered cans by U.S. food processors. The major source of lead in drinking water is from lead pipes used in household plumbing. The CDC revised its guidelines concerning childhood lead poisoning, stating that community prevention activities should be triggered when a large percentage of children in a community have blood lead levels of 10 micrograms/dl, the lowest level at which neurodevelopmental effects were believed to occur. For children with blood lead level concentrations between 10 and 14 micrograms/dl, more frequent rescreening may be needed. For concentrations between 15 and 19 micrograms/dl, in addition to more frequent screening, nutritional and educational advice should be given. In cases where these levels persist, there should be environmental investigation and intervention. All children with blood levels of 20 micrograms/dl or greater should receive environmental evaluation and medical examination. Such children may need pharmacological treatment.

Australia↗
PubMed1998

The influence of bone and blood lead on plasma lead levels in environmentally exposed adults.

There is concern that previously accumulated bone lead stores may constitute an internal source of exposure, particularly during periods of increased bone mineral loss (e.g., pregnancy, lactation, and menopause). Furthermore, the contribution of lead mobilized from bone to plasma may not be adequately reflected by whole-blood lead levels. This possibility is especially alarming because plasma is the main circulatory compartment of lead that is available to cross cell membranes and deposit in soft tissues. We studied 26 residents of Mexico City who had no history of occupational lead exposure. Two samples of venous blood were collected from each individual. One sample was analyzed by inductively coupled plasma-magnetic sector mass spectrometry for whole-blood lead levels. The other sample was centrifuged to separate plasma, which was then isolated and analyzed for lead content by the same analytical technique. Bone lead levels in the tibia and patella were determined with a spot-source 109Cd K-X-ray fluorescence instrument. Mean lead concentrations were 0.54 microg/l in plasma, 119 microg/l in whole blood, and 23.27 and 11.71 microg/g bone mineral in the patella and tibia, respectively. The plasma-to-whole-blood lead concentration ratios ranged from 0.27% to 0.70%. Whole-blood lead level was highly correlated with plasma lead level and accounted for 95% of the variability of plasma lead concentrations. Patella and tibia lead levels were also highly correlated with plasma lead levels. The bivariate regression coefficients of patella and tibia on plasma lead were 0.034 (p<0. 001) and 0.053 (p<0.001), respectively. In a multivariate regression model of plasma lead levels that included whole-blood lead, patella lead level remained an independent predictor of plasma lead level (ss = 0.007, p<0.001). Our data suggest that although whole-blood lead levels are highly correlated with plasma lead levels, lead levels in bone (particularly trabecular bone) exert an additional independent influence on plasma lead levels. It will be important to determine whether the degree of this influence increases during times of heightened bone turnover (e.g., pregnancy and lactation).

Adult↗
PubMed1997

Contamination of houses by workers occupationally exposed in a lead-zinc-copper mine and impact on blood lead concentrations in the families.

OBJECTIVE: To evaluate the pathway of leaded dust from a lead-zinc-copper mine to houses of employees, and the impact on blood lead concentrations (PbB) of children. METHODS: High precision lead isotope and lead concentration data were obtained on venous blood and environmental samples (vacuum cleaner dust, interior dustfall accumulation, water, paint) for eight children of six employees (and the employees) from a lead-zinc-copper mine. These data were compared with results for 11 children from occupationally unexposed control families living in the same city. RESULTS: The median (range) concentrations of lead in vacuum cleaner dust was 470 (21-1300) ppm. In the houses of the mine employees, vacuum cleaner dust contained varying higher proportions of mine lead than did airborne particulate matter measured as dustfall accumulated over a three month period. The median (range) concentrations of lead in soil were 30 (5-407) ppm and these showed no evidence of any mine lead. Lead in blood of the mine employees varied from 7 to 25 micrograms/dl and was generally dominated by mine lead (> 60%). The mean (SD) PbB in the children of the mine employees was 5.7 (1.7) micrograms/dl compared with 4.1 (1.4) micrograms/dl for the control children (P = 0.02). The PbB of all children was always < 10 micrograms/dl, the Australian National Health and Medical Research Council goal for all Australians. Some of the control children had higher PbB than the children of mine employees, probably from exposure to leaded paint as six of the eight houses of the control children were > 50 years old. In five of the eight children of mine employees > 20% of PbB was from the lead mine. However, in the other three cases of children of mine employees, their PbB was from sources other than mine lead (paint, petrol, background sources). CONCLUSIONS: Houses of employees from a lead mine can be contaminated by mine lead even if they are not situated in the same place as the mine. Delineation of the mine to house pathway indicates that lead is probably transported into the houses on the clothes, shoes, hair, skin, and in some cases, motor vehicles of the workers. In one case, dust shaken from clothes of a mine employee contained 3000 ppm lead which was 100% mine lead. The variable contamination of the houses was not expected given the precautions taken by mine employees to minimise transportation of lead into their houses. Although five out of the eight children of mine employees had > 20% mine lead in their blood, in no case did the PbB of a child exceed the Australian National Health and Medical Research Council goal of 10 micrograms/dl. In fact, some children in the control families had higher PbB than children of mine employees. In two cases, this was attributed to a pica habit for paint. The PbB in the children of mine employees and controls was independent of the source of lead. The low PbB in the children of mine employees may reflect the relatively low solubility (bioavailability) of the mine dust in 0.1 M hydrochloric acid (< 40 %), behaviour--for example, limited mouthing activity--or diet.

Adult↗
PubMed2004

Transition of cord blood lead level, 1985-2002, in the Taipei area and its determinants after the cease of leaded gasoline use.

Lead has long been of concern for its toxicity, impairment of neurobehavioral and cognitive development, and electrophysiological deficits in children, even at levels less than 10 microg/dL. The present study was conducted to elucidate the extent of cord blood lead level decline in the Taipei area from 1985 to 2002 and to explore the factors affecting the cord blood lead level after the cease of leaded gasoline use. In the current study period of 2001-2002, 184 of 1310 newborns delivered in the Taipei Municipal Women and Children Hospital between September 2001 and August 2002 were eligible and randomly selected to participate in this study. Neither of their parents had an occupational lead exposure history. At each delivery, a sample of 5-10 mL umbilical cord blood was collected for lead determination by graphite furnace atomic absorption spectrometry. The cord blood lead level of the newborns in the current study period averaged 2.35 +/- 1.12 microg/dL. Together with the cord blood lead averages of 7.48 +/- 2.25 and 3.28 +/- 1.52 microg/dL obtained from two previous surveys conducted in 1985-1987 and 1990-1992, respectively, the cord blood lead level was significantly decreased (P < 0.005). It is estimated that such a reduction in cord blood lead from 7.48 to 2.35 microg/dL for each year's cohort of 260,000 newborns in Taiwan might benefit the economics, ranging from US$8.9 billion to US$12.1 billion by improving the worker productivity. For the time period from 1985 to 2002, there were consistent transition patterns among the yearly fluctuations of air lead level, leaded gasoline consumption, lead content in gasoline, estimated lead amount emitted from the consumed leaded gasoline, and average cord blood lead levels of the three respective study periods. Additionally, every 0.1-g/L reduction in lead content in gasoline might lead to a lowering of cord blood lead level by 1.78 microg/dL. Furthermore, at low level of around 2 microg/dL, a multiple regression analysis demonstrated that economic status was the most influential factor for cord blood lead variation (P = 0.0061) while the maternal working month during her pregnancy was retained in the model with borderline effect (P = 0.0625). After accounting for the effect of leaded gasoline on the cord blood lead level, future study to differentiate the primary contributors for the low-level cord blood lead variation around 1-2 microg/dL is warranted.

Adult↗
PubMed2000

Public health implications of new guidelines for lead in drinking water: a case study in an area with historically high water lead levels.

Concern about the neurotoxicity of lead, particularly in infants and young children, has led to a revision of blood lead levels which are considered to involve an acceptable level of human exposure. Drinking water guidelines have also been reviewed in order to reduce this source of population exposure to lead. In the last 20 years, guidelines have been reduced from 100 to 50 to 10 microg/litre. Lead in tap water used to be a major public health problem in Glasgow because of the high prevalence of houses with lead service pipes, the low pH of the public water supply and the resulting high levels of lead in water used for public consumption. Following two separate programmes of water treatment, involving the addition of lime and, a decade later, lime supplemented with orthophosphate, it is considered that maximal measures have been taken to reduce lead exposure by chemical treatment of the water supply. Any residual problem of public exposure would require large scale replacement of lead service pipes. In anticipation of the more stringent limits for lead in drinking water, we set out to measure current lead exposure from tap water in the population of Glasgow served by the Loch Katrine water supply, to compare the current situation with 12 years previously and to assess the public health implications of different limits. The study was based on mothers of young children since maternal blood lead concentrations and the domestic water that mothers use to prepare bottle feeds are the principal sources of foetal and infant lead exposure. An estimated 17% of mothers lived in households with tap water lead concentrations of 10 microg/litre (the [WHO,] guideline) or above in 1993 compared with 49% in 1981. Mean maternal blood lead concentrations fell by 69% in 12 years. For a given water lead concentration, maternal blood lead concentrations were 67% lower. The mean maternal blood lead concentration was 3.7 microg/litre in the population at large, compared with 3.3 microg/litre in households with negligible or absent tap water lead. Nevertheless, between 63% and 76% of cases of mothers with blood lead concentrations of 10 microg/dl or above were attributable to tap water lead. The study found that maternal blood lead concentrations were well within limits currently considered safe for human health. About 15% of infants may be exposed via bottle feeds to tap water lead concentrations that exceed the WHO guideline of 10 microg/litre. In the context of the health and social problems which affect the well-being and development of infants and children in Glasgow, however, current levels of lead exposure are considered to present a relatively minor health problem.

Adult↗
PubMed1998

Changes in pacing lead impedance over time predict lead failure.

It has been suggested that a decrease in lead impedance may predict pacing lead failure, but there is limited prospective data about the relation of changes in lead impedance over time to lead performance. We monitored changes in lead impedance through implantable pulse generators with real-time telemetry data capability in 105 patients with Medtronic 4012 leads (n = 38) and Medtronic 4004 leads (n = 67). Pacing lead failure was documented by serial ambulatory electrocardiographic monitoring or intensified pacemaker clinic surveillance. A significant decrease in lead impedance was observed in patients with Medtronic 4012 and Medtronic 4004 leads with documented lead failure, whereas lead impedance remained stable over time in patients without documented lead failure. The sensitivity and specificity of a lead impedance decrease of > or =15% to predict lead failure were 69% and 70%, respectively. The sensitivity and specificity of a lead impedance decrease of > or =30% to predict lead failure were 36% and 90%, respectively. The positive and negative predictive values for a lead impedance decrease of > or =15% were 54% and 81%, respectively, and for a lead impedance decrease of > or = 30% were 65% and 73%, respectively. Thus, small decreases in lead impedance may identify failing leads. Serial measurement of pacing lead impedance over time is a useful tool to monitor pacing lead performance.

Aged↗
PubMed2001

Ancillary tools in pacemaker and defibrillator lead extraction using a novel lead removal system.

A previous report described our preliminary experience with a highly successful pacing lead removal system (VasoExtor). Extending this experience, we found it necessary to use additional tools to enhance the success of percutaneous lead extraction with this system. In the present series, we used the standard locking stylets (S and K), and recently, one newer type of stylet (Magic) over the last 3 years in 34 patients to extract 48 pacemaker leads in 31 patients and 3 defibrillator (ICD) leads in 3 patients. Lead extraction was carried out in 23 men and 11 women (aged 64 +/- 17 years) because of pacemaker infection (n = 21), pacemaker (n = 8) or ICD (n = 3) lead malfunction, or prior to ICD implant (n = 2). Leads were in place for 3.5 +/- 3.7 years. Infections, involving pocket and lead(s), were due to S. epidermidis (n = 13), S. aureus (n = 6), S. aureus plus E. coli (n = 1), for fungi (n = 1). Of the 48 pacing leads, 31 were ventricular, 15 atrial, and 2 were VDD leads. The ICD leads were two double-coil leads (CPI) and one single-coil lead (Telectronics). Using the S (n = 12), K (n = 8), or Magic (n = 3) stylets, all pacing leads in 23 patients and the ICD leads in 2 patients were successfully removed from a subclavian approach using the locking stylets. However, in nine (26.5%) patients ancillary tools were required. In four patients, lead fragments were captured with use of a noose catheter, a pigtail catheter, and a bioptome from a right femoral approach. In two patients, locking could not be effected and a noose catheter from the right femoral vein was used, aided by a pigtail and an Amplatz catheter and a bioptome to remove three leads. In a patient with an ICD lead, a combined subclavian (stylet S) and right femoral approach (noose catheter) was required. In a patient with a dysfunctional ventricular lead 12 years old, a motor drive unit was used to facilitate the exchange of locking stylets, but extraction failed. In another patient, a fragment of a dysfunctional ventricular lead remained intravascularly despite resorting to a femoral approach. Finally, lead removal was completely (32/34, 94%) or partially (1/34, 3%) successful in 33 (97%) of 34 patients for 50 (98%) of 51 leads without complications. In conclusion, to enhance the success of pacing or ICD lead extraction with use of the VascoExtor locking stylets, an array of ancillary tools were required in more than one fourth of patients.

Adult↗
PubMed1976

Lead in tissues of mallard ducks dosed with two types of lead shot.

Mallard ducks (Anas platyrhynchos) were sacrificed one month after ingesting one number 4 all-lead shot or one number 4 lead-iron shot. Livers, kidneys, blood, wingbones, and eggs were analyzed for lead by atomic absorption. Necropsy of sacrificed ducks failed to reveal any of the tissue lesions usually associated with lead poisoning in waterfowl. Lead levels in ducks given all-lead shot averaged about twice those in ducks given lead-iron shot, reflecting the amount of lead in the two types of shot. Lead in the blood of ducks dosed with all-lead shot averaged 0.64 ppm, and 0.28 ppm in ducks given lead-iron shot. Lead residues in livers and kidneys of females given all-lead shot were significantly higher than in males. In both dosed groups, lead levels in wingbones of females were about 10 times those in males, and were significantly correlated with the number of eggs laid after dosage. Lead levels in contents and shells of eggs laid by hens dosed with all-lead shot were about twice those in eggs laid by hens dosed with lead-iron shot. Eggshells were found to best reflect levels of lead in the blood. Our results indicate that mallards maintained on a balanced diet and dosed with one lead shot may not accumulate extremely high lead levels in the liver and kidney. However, extremely high lead deposition may result in the bone of laying hens after ingesting sublethal amounts of lead shot as a result of mobilization of calcium from the bone during eggshell formation.

Animals↗
PubMed1983

[Biliary excretion of diethyl lead after administration of tetraethyl lead in rabbits].

In order to investigate into whether the large amount of inorganic lead excreted into the feces following intravenous injection of tetraethyl lead to rabbits is derived from the diethyl lead excreted into the bile, we administered 12 mg/kg of tetraethyl lead to rabbits which had been fistulated into the bile duct for taking the bile out of the body. The total lead excreted into the bile during the first 24 hours after the injection of tetraethyl lead amounted to about 8% of the injected amount of lead (with 97% of the excreted lead made up of diethyl lead). The amount of total lead contained in the cecal contents of unfistulated rabbits 24 hours after the injection of tetraethyl lead was equivalent to about 12% of the injected amount of lead (with inorganic lead accounting for about 90% of the excreted lead), but the counterpart of the fistulated rabbits was equivalent only to about 0.6%. The amount of lead excreted into the bile, when measured in terms of the total lead content of the liver, was slightly less in the fistulated rabbits than in the unfistulated ones. These findings indicated that the amount of total lead excreted into the bile of the fistulated rabbits was almost the same as that contained in the cecal contents of unfistulated rabbits, and that the major portion of the lead contained in the cecal contents or feces was composed of inorganic lead. From these results, we came to the conclusion that the large amount of inorganic lead detected in the feces after the injection of tetraethyl lead is derived from the diethyl lead excreted into the bile.

Animals↗
PubMed1993

Lead-contaminated soil abatement and urban children's blood lead levels.

OBJECTIVE: To test the hypothesis that a reduction of 1000 ppm or more of lead in soil accessible to children would result in a decrease of at least 0.14 mumol/L (3 micrograms/dL) in blood lead levels. SETTING: Urban neighborhoods with a high incidence of childhood lead poisoning and high soil lead levels. DESIGN: Randomized controlled trial of the effects of lead-contaminated soil abatement on blood lead levels of children followed up for approximately 1 year after the intervention. PATIENTS: A total of 152 children less than 4 years of age with venous blood lead levels of 0.34 to 1.16 mumol/L (7 to 24 micrograms/dL). Children were largely poor and had a mean age at baseline of 32 months, a mean blood lead level of 0.60 mumol/L (12.5 micrograms/dL), and a median surface soil lead level of 2075 ppm. INTERVENTIONS: Children were randomized to one of three groups: the study group, whose homes received soil and interior dust abatement and loose paint removal; comparison group A, whose homes received interior dust abatement and loose paint removal; and comparison group B, whose homes received only interior loose paint removal. MAIN OUTCOME MEASURES: Change in children's blood lead levels from preabatement levels to levels approximately 6 and 11 months after abatement. RESULTS: The mean decline in blood lead level between preabatement and 11 months after abatement was 0.12 mumol/L (2.44 micrograms/dL) in the study group (P = .001), 0.04 mumol/L (0.91 microgram/dL) in group A (P = .04), and 0.02 mumol/L (0.52 microgram/mL) in group B (P = .31). The mean blood lead level of the study group declined 0.07 mumol/L (1.53 micrograms/dL) more than that of group A (95% confidence interval [CI], -0.14 to -0.01 mumol/L [-2.87 to -0.19 micrograms/dL]) and 0.09 mumol/L (1.92 micrograms/dL) more than group B (95% CI, -0.16 to -0.03 mumol/L [-3.28 to -0.56 micrograms/dL]). When adjusted for preabatement lead level, the 11-month mean blood lead level was 0.06 mumol/L (1.28 micrograms/dL) lower in the study group as compared with group A (P = .02) and 0.07 mumol/L (1.49 micrograms/dL) lower than in group B (P = .01). The magnitude of the decline independently associated with soil abatement ranged from 0.04 to 0.08 mumol/L (0.8 to 1.6 micrograms/dL) when the impact of potential confounders, such as water, dust, and paint lead levels, children's mouthing behaviors, and other characteristics, was controlled for. CONCLUSIONS: These results demonstrate that lead-contaminated soil contributes to the lead burden of urban children and that abatement of lead-contaminated soil around homes results in a modest decline in blood lead levels. The magnitude of reduction in blood lead level observed, however, suggests that lead-contaminated soil abatement is not likely to be a useful clinical intervention for the majority of urban children in the United States with low-level lead exposure.

Child, Preschool↗
PubMed2005

Blood lead levels in lactating cows reared around polluted localities; transfer of lead into milk.

Lead is pervasive environmental pollutant with potential public health hazard as a contaminant of food from animal origin. The present study examines the blood and milk lead level in animals reared in areas around different industrial activities and to find out correlation between blood and milk lead levels in lactating cows. Blood and milk samples (n = 149) were collected from animals reared around steel processing unit (n = 22), lead-zinc smelter (n = 21), aluminum processing plant (n = 25), rock phosphate mining area cum phosphate fertilizer plant (n = 21), coal mining areas (n = 46) and closed lead but functional zinc smelter (n = 14). Samples were also collected from randomly chosen 52 lactating cows reared in non-polluted areas to serve as controls. Significantly (P < 0.05) higher blood lead level was recorded in animals reared around lead-zinc smelting factories followed by closed lead but functional zinc smelter, aluminum processing unit and steel manufacturing plant, as compared to values recorded for control animals. The highest milk lead level (0.84 +/- 0.11 microg/ ml) was detected in animals reared in the vicinity of lead-zinc smelting unit followed by aluminum processing plant and steel processing unit. Analysis of correlation between blood lead levels and lead excretion in milk through sorting the blood lead values into 9 different ranges irrespective of site of collection of samples (n = 201) revealed significant correlation (r = 0.469 at P < 0.01) between blood and milk lead concentrations. The lactating cows with blood lead levels above 0.20 microg/ml (groups 5-9) had significantly (P < 0.05) higher milk lead excretion than those with blood lead levels from non detectable to 0.20 microg/ml (groups 1-4). Pearson correlation analysis between blood and milk lead concentrations in 122 animals with blood lead <0.20 microg/ml showed non-significant correlation (r = 0.030 at P < 0.05) but a significant correlation was observed between these two parameters with blood lead level above >0.02 microg/ml indicating that the excretion of lead through milk increases with the increased in blood lead level above 0.20 microg/ml.

Animal Feed↗
PubMed1999

Predictors of dimercaptosuccinic acid chelatable lead and tibial lead in former organolead manufacturing workers.

OBJECTIVES: To identify predictors of tibial and dimercaptosuccinic acid (DMSA) chelatable lead in 543 organolead manufacturing workers with past exposure to organic and inorganic lead. METHODS: In this cross sectional study, tibial lead (by 109Cd K-shell x ray fluorescence), DMSA chelatable lead (4 hour urinary lead excretion after oral administration of 10 mg/kg), and several exposure measures were obtained on study participants, mean (SD) age 57.6 (7.6) years. RESULTS: Tibial lead concentrations ranged from -1.6 to 52.0 micrograms lead/g bone mineral, with a mean (SD) of 14.4 (9.3) micrograms/g. DMSA chelatable lead ranged from 1.2 to 136 micrograms, with a mean (SD) of 19.3 (17.2) micrograms. In a multiple linear regression model of tibial lead, age (p < 0.01), duration of exposure (p < 0.01), current (p < 0.01) and past (p = 0.05) cigarette smoking, and diabetes (p = 0.01) were all independent positive predictors, whereas height (p = 0.03), and exercise inducing sweating (p = 0.04) were both negative predictors. The final regression model accounted for 31% of the variance in tibial lead concentrations; 27% was explained by age and duration of exposure alone. DMSA chelatable lead was directly associated with tibial lead (p = 0.01), cumulative exposure to inorganic lead (y.microgram/m3, p = 0.01), current smoking (p < 0.01), and weight (p < 0.01), and negatively associated with diabetes (p = 0.02). The final model accounted for 11% of the variance in chelatable lead. When blood lead was added to this model of DMSA chelatable lead, tibial lead, cumulative exposure to inorganic lead, and diabetes were no longer significant; blood lead accounted for the largest proportion of variance (p < 0.001); and the total model r2 increased to 19%. CONCLUSIONS: The low proportions of variance explained in models of both tibial and chelatable lead suggest that other factors are involved in the deposition of lead in bone and soft tissue. In epidemiological studies of the health effects of lead, evaluation of associations with both these measures may allow inferences to be made about whether health effects are likely to be recent, and thus potentially reversible, or chronic, and thus possibly irreversible. The data also provide direct evidence that in men the total amount of lead in the body that is bioavailable declines with age.

Adult↗
PubMed1999

Influence of bone-lead stores on the observed effectiveness of lead hazard intervention.

Lead hazard interventions have reduced children's blood-lead concentrations, but do not eliminate lead altogether from the bloodstream. Several studies suggest that blood-lead concentrations, measured 6 to 12 months after such interventions, decline by approximately 25%. The Environmental Protection Agency is preparing to promulgate a rule prescribing residential lead levels in paint, dust, and soil that constitute a lead-based paint hazard. Such a rule will prompt interventions of primary prevention character (i.e., precluding exposure before it occurs) rather than the secondary prevention character interventions (i.e., alleviating exposure after it has adversely affected the resident child) documented in the literature. It is important to attempt to estimate the efficacy achieved from the primary prevention interventions prompted by the rule's promulgation. As bone-lead stores represent the principal confounding factor to relating secondary prevention results to primary prevention, this paper addresses the impact of lead stored in bone, which may later be released to the blood and other parts of the child's body. A simple, but thoroughly documented, modeling exercise is presented to estimate the maximum length of time for which bone-lead stores alone could account for continuing elevated blood-lead levels observed in children following an intervention. The approach is based on a two-compartment model for the transfer of lead between blood and bone tissues within the body and the elimination of lead from the body. Modeling results suggest that bone-lead mobilization can impact blood-lead levels of young children for considerably long periods following an intervention. These results may explain the seemingly contradictory fact that low declines in blood-lead concentrations are observed despite the significant reduction in residential dust-, paint-, and soil-lead levels observed following lead hazard interventions. An intervention which reduces a 5-year-old child's total lead exposure by 50% might, due to mobilized bone-lead stores, produce only a 25% decline in the child's blood-lead concentrations measured 12 months following the intervention. The results also suggest, however, that those intervention strategies for which less than 25% declines were observed 12 months following the intervention likely eliminated less than 50% of the children's total lead exposure.

Bone and Bones↗
PubMed2002

Influence of nutrient intake on blood lead levels of young children at risk for lead poisoning.

Although removal of lead paint hazards from at-risk houses remains the primary means of preventing elevated blood lead among young children, reduction of risk through nutritional factors has also been of interest. In this study we evaluated the effect of nutrient intake on blood lead levels by analyzing whether the intakes of certain dietary components a) were associated with blood lead levels independent of lead exposure or b) modified the effect of lead exposure on blood lead. Subjects were 205 children from low-income families who were approximately 1 year of age and living in old, urban houses. The data collected for each child included blood lead level, nutritional status, and amount of lead exposure, which was assessed from samples of household dust. Multiple linear regression analyses showed a statistically significant positive association between lead exposure and blood lead. Statistically significant positive associations were found between blood lead and total fat as well as blood lead and saturated fat, independent of lead exposure and age of the child. Regression modeling and stratified analysis showed that mean blood lead increased with increasing lead exposure as well as with increasing caloric intake, suggesting that caloric intake modifies the association between lead exposure and blood lead. The findings from this study, if replicated in other studies, support a dietary intervention to reduce the amount of total calories, total fat, and saturated fat among children 1 year of age at risk for lead exposure, while maintaining adequate intake of these dietary components. Our results also reinforce recommendations that removal of lead paint hazards from at-risk houses should be the primary means of preventing lead exposure.

Adolescent↗
PubMed2005

Blood lead levels in lactating cows reared around polluted localities; transfer of lead into milk.

Lead is pervasive environmental pollutant with potential public health hazard as a contaminant of food from animal origin. The present study examines the blood and milk lead level in animals reared in areas around different industrial activities and to find out correlation between blood and milk lead levels in lactating cows. Blood and milk samples (n=149) were collected from animals reared around steel processing unit (n=22), lead-zinc smelter (n=21), aluminum processing plant (n=25), rock phosphate mining area cum phosphate fertilizer plant (n=21), coal mining areas (n=46) and closed lead but functional zinc smelter (n=14). Samples were also collected from randomly chosen 52 lactating cows reared in non-polluted areas to serve as controls. Significantly (P<0.05) higher blood lead level was recorded in animals reared around lead-zinc smelting factories followed by closed lead but functional zinc smelter, aluminum processing unit and steel manufacturing plant, as compared to values recorded for control animals. The highest milk lead level (0.84+/-0.11 microg/ml) was detected in animals reared in the vicinity of lead-zinc smelting unit followed by aluminum processing plant and steel processing unit. Analysis of correlation between blood lead levels and lead excretion in milk through sorting the blood lead values into nine different ranges irrespective of site of collection of samples (n=201) revealed significant correlation (r=0.469 at P<0.01) between blood and milk lead concentrations. The lactating cows with blood lead levels above 0.20 microg/ml (Groups 5 to 9) had significantly (P<0.05) higher milk lead excretion than those with blood lead levels from non-detectable to 0.20 microg/ml (Groups 1 to 4). Pearson correlation analysis between blood and milk lead concentrations in 122 animals with blood lead 0.20 microg/ml indicating that the excretion of lead through milk increases with the increase in blood lead level above 0.20 microg/ml.

Animal Feed↗
PubMed2000

Predictors of lead absorption in children of lead workers.

OBJECTIVES: This study was conducted to determine whether children of lead workers are at a higher risk of lead absorption and if so, to identify risk factors for absorption, including lifestyle, household, environmental and parental work practices with lead. METHODS: This cross-sectional study recruited 17 'lead worker' and 13 comparison 'non-lead worker' households. Companies and eligible employees were contacted using mail-out packs. Children were aged between 12 and 72 months. Data collection involved administration of a questionnaire and collection of dust, soil, water, paint-scraping samples, and blood from the children for the determination of lead and ferritin levels. Statistical analysis was performed using SPSS. RESULTS: Participants included seven of 29 eligible employees from 14 'scheduled' lead workplaces and 12 of 19 eligible employees from 19 'leadlighter' workplaces identified. The average lead level for workers was 13.9 micrograms/dl, children of lead workers 6.93 micrograms/dl (n = 22) and comparison group 3.93 micrograms/dl (n = 16). Water lead levels were all < 2.5 ppm. The lead content of three soil samples and nine dust samples was above suggested guideline levels. Lead levels were significantly higher in children of lead workers but all were within recommended levels. Inadequate practice of lead work hygiene measures, such as inadequate use of protective equipment and taking work clothes home, was a common factor in lead worker households that were found to have elevated soil and dust lead levels. The differences in lead levels between groups did not change significantly when adjustment was made for the clustering effect of more than one child per household. CONCLUSIONS: Children of lead workers are at higher risk of lead absorption. Poor work hygiene practices of lead workers suggest an association with elevated lead levels in their children. A number of other predictors were suggested by this study but the small numbers of participants made it difficult to detect statistically significant differences between subgroups.

Adult↗
PubMed1997

Effects of low level exposure to lead on neurophysiological functions among lead battery workers.

OBJECTIVES: Assessment of neurophysiological functions in workers with low level exposure to lead and evaluation of the efficacy of bone lead measurements in the prediction of effects of lead. METHODS: Exposure to lead of 60 workers from a lead battery battery factory was estimated from historical blood lead measurements and analysis of lead in the tibial and calcaneal bones with x ray fluorescence. Peripheral and central nervous system functions were assessed by measuring conduction velocities, sensory distal latencies, sensory amplitudes, and vibration thresholds as well as by quantitative measurement of the absolute and relative powers and mean frequencies of different electroencephalograph (EEG) channels. RESULTS: Sensory amplitudes, and to a smaller degree sensory or motor conduction velocities, showed a negative correlation with long term exposure to lead, most clearly with integrated blood lead concentration and exposure time. Vibration thresholds measured in the arm were related to recent exposure to lead, those measured in the leg to long term exposure. The alpha and beta activities of the EEG were more abundant in subjects with higher long term exposure to lead. Calcaneal lead content reflected short term exposure, tibial lead content reflected long term exposure. Blood lead history showed a closer relation with effects of lead than the tibial or calcaneal lead concentrations. CONCLUSIONS: Vibratory thresholds, quantitative EEG, and to a smaller extent the sensory amplitude, provide sensitive measures of effects of lead in occupationally exposed adults. Most accurate estimates of health risks induced by lead can be obtained from a good history of blood lead measurements. If such a history of blood lead concentrations is not available, analysis of bone lead may be used for the assessment of health risks.

Adult↗