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PubMed1998

A suggestion for unification of present limb lead systems into a single "F" lead system.

In this paper it is intended to unify the standard lead and the augmented unipolar limb lead (aV lead) system into a single lead system. Viewing from the angle of lead axes, the standard leads and the aV leads are not only reflecting the frontal plane vector, but are also actually complementary to each other. By now it has become quite obvious that they not only can, but also should be unified into a single system. Viewing these six leads (from standard lead and aV lead systems), starting from aVL, lead I, reversed aVR, lead II, aVF to lead III, an arc including approximately 150 degrees is formed. It is suggested that this unified system may be called "F" system with each of the above leads renamed as F1-F6 leads, respectively, since they are all reflecting the vectors of the frontal plane. In this F-lead system each lead is approximately 30 degrees apart. If such a system would be adopted it is only necessary to time the amplitude of the P, QRS and T of aV lead by 1.15 (a figure calculated by vector analysis). If this suggestion is widely adopted there will be only a F lead system for the frontal vectors and the present V system for the "horizontal" vectors in the electrocardiogram.

Electrocardiography↗
PubMed2004

Association between aminolevulinate dehydrase genotypes and blood lead levels in children from a lead-contaminated area in Antofagasta, Chile.

Childhood environmental lead exposure in the city of Antofagasta, Chile, was generated by the accumulation of recently removed lead stores derived from mining activities for a long period of time. Susceptibility to harmful lead effects may be associated with polymorphisms of delta-aminolevulinic acid dehydratase (ALAD) because of the differential binding of lead to the codified proteins. We assessed the associations and possible interactions among the following variables: blood lead levels, ALAD genotypes, and distance to the source of lead contamination in Chilean children exposed to lead contamination in Antofagasta, Chile. Ninety-three children were recruited from schools located near a lead- contaminated area. Lead blood levels were measured by atomic absorption spectrophotometry. ALAD genotypes were determined by polymerase chain reaction and restriction fragment-length polymorphism analysis. The frequency of the ALAD-2 allele was estimated at 0.054. Children with the ALAD-2 genotype had higher blood lead levels than noncarriers (p = 0.06). As expected, blood lead levels were inversely correlated with the distance from lead stores. Interestingly, ALAD-2 carriers were more frequent within the area defined by a distance of 200 m from lead deposits (27%) than in areas >200 m (5%) away. Children living within a maximum distance of 200 m from the lead stores showed higher blood lead levels in ALAD-2 carriers (geometric mean = 16.4 microg/dl, range 6 to 27) than in noncarriers (geometric mean = 12.1 microg/dl, range 0 to 26) without achieving statistical significance (p = 0.13). A trend for higher blood lead levels in ALAD-2 carriers compared with ALAD-1 homozygous children has been observed. Because ALAD-2 frequency was higher in subjects living within 200 m from the lead deposits, we hypothesized that a long-term selective pressure against the presence of the ALAD-1 allele is the cause of the overrepresentation of the ALAD-2 allele in children living in proximity to the recently removed lead stores.

Child↗
PubMedDate not supplied

Hygiene- and food-related behaviors associated with blood lead levels of young children from lead-contaminated homes.

Exposures associated with blood lead levels greater than 40 micrograms/dL in young children who live in lead-contaminated homes have been well documented. As the action level for lead is reduced, activities that contribute to lower levels of lead exposure must be identified. A child's eating habits and related hygiene behaviors are major hand-to-mouth activities that have been largely overlooked in the study of activities contributing to lead ingestion. To examine this subject, a survey questionnaire for caretakers of young children was developed. The objective of the questionnaire was to characterize food-related activities of young children and to identify behavioral indicators of lead exposure. The association between food- and hygiene-related behaviors and blood lead levels among 60 children between 13 and 36 months old with low-to-moderate blood lead levels was examined in homes that had been identified as containing lead in paint and house dust. The participants were enrolled in the Children's Lead Exposure and Reduction Study in Jersey City, New Jersey. Blood lead levels of children 13-24 months old did not differ significantly from those of children 25-36 months of age (10.1 and 11.3 micrograms/dL, respectively). Differences in eating habits and hygiene behaviors were found for the two age groups. Bivariate analyses found that the primary behavioral indicators of blood lead levels were determined by whether the child prepared his/her own food and whether the child ate food that had been on the floor. This factor was dependent on age. Children 13-24 months old had significantly elevated blood lead levels if these behaviors exhibited. No significant differences were found, however, for children 25-36 months old. Several food-related habits were also associated with blood lead levels. Eating hamburgers, doughnuts, peanut butter and jelly sandwiches, and cold cuts were associated with elevated blood lead levels in 13-24-month-old children, while eating vitamins, raw vegetables, and yogurt were associated with lower blood lead levels in this age group. For children 25-36 months old, eating hamburgers and peanut butter and jelly sandwiches was associated with elevated blood lead levels, while yogurt consumption was associated with lower blood lead levels.

Age Factors↗
PubMed1994

Absolute bioavailability of lead acetate and mining waste lead in rats.

The primary purpose of this study was to generate data that could be used to determine the absolute bioavailability of lead using data from a previous study in which soil containing lead from mining waste was mixed with feed. Young male and female Sprague-Dawley rats (7-8 weeks of age, five/sex/group) were given either soluble lead acetate mixed in a purified diet (AIN-76) at three different dose levels (1, 25, and 250 ppm Pb for 30 consecutive days) or intravenously at doses of 0.02, 0.20, and 2.0 mg Pb/kg BW for 29 days. A control group (purified diet only) was also included. The intravenous groups were used to provide maximal absorption (lead presumed to be 100% bioavailable) and accumulation data for lead in blood, bone, and liver. The lead acetate groups were used to evaluate the comparability of the present study with a previous study that compared bioavailable lead from ingested soil and lead acetate. Group mean whole blood, bone and liver lead concentration values increased with increasing dose levels for all treatment groups. A linear relationship was observed between blood lead concentration and dose following intravenous administration of lead and this provided empirical support for using blood lead concentrations at supposed steady state (approximately 30 days) to compute the bioavailability of lead administered by different routes and from different sources. The absolute bioavailability values of mining waste lead in soil were low based on the results for all tissue types. Absolute bioavailability values for lead acetate in dosed feed for blood, bone, and liver were approximately 6-, 19-, and 20-fold greater, respectively, than mining waste lead. Based on the current design and test system used, the absolute bioavailability of mining waste lead in soil administered in feed was approximately 3% based on blood data and less than 1% based on bone and liver data. These data are consistent with the low solubility of the constituent lead mineral phases in Butte soils.

Administration, Oral↗
PubMed2001

Lead contamination of seabirds harvested with lead shot--implications to human diet in Greenland.

Lead contamination of seabirds from the use of lead shot in Greenland was studied in thick-billed murre hunted at Nuuk in November 1998. In each bird shot pellets were located and counted using X-ray. The birds were skinned and viscera, head, wings and legs removed, after which the carcass was cooked. The soup and breast meat were then analyzed for lead after removal of visible shot pellets. In the soup the lead concentration was quite low, mean 6.3 micrograms/l (95% confidence interval between 4.4 and 8.2 micrograms/l), whereas breast meat lead values have a mean of 0.22 microgram/g (wet weight basis; 95% confidence interval between 0.10 and 0.36 microgram/g). This is more than 10 times higher than in birds not killed with lead shot. We found no correlation between lead concentration measured and number of pellets recorded in the whole bird or in the soup or in meat. The study indicates that lead in the meat exists as small lead fragments, left during the passage of pellets through the breast. Because of inhomogeneous lead distribution in samples, the uncertainty of estimated lead concentration in breast meat is high. Based on this study, it is concluded that birds killed with lead shot are a significant source of lead, probably the most important single source, of the diet of many people in Greenland. We estimate an intake of 50 micrograms lead from eating one boiled murre with soup. In addition people will occasionally eat whole lead shot pellets which have documented health effects. An intake of 50 micrograms lead is about twice as much as the daily average lead intake from all dietary sources in Denmark, about 25 times the daily lead intake from other marine food items in Greenland, and about one-fourth of the accepted tolerable daily intake.

Animals↗
PubMed1995

Lead in tissues of deceased lead smelter workers.

Smelter workers are exposed to a number of metals and other substances in dust, fumes and gases. The concentrations of lead in liver, lung, kidney, brain, hair and nails were determined in 32 deceased, long-term exposed male lead smelter workers, and compared with those of 10 male controls. The lead levels in liver, lung, kidney and brain were analyzed by atomic absorption spectrophotometry. X-ray fluorescence was used for the determinations in hair and nails. Lead in blood had been determined repeatedly in the lead workers since 1950, which made it possible to calculate a time-integrated blood lead index for each worker. The highest lead levels in soft tissues were found in liver, followed in order of concentration by kidney, lung and brain, among both exposed workers and controls. These organ lead concentrations were all significantly higher among the workers as compared with the control group (p < or = 0.02). The largest difference between workers and controls was found in brain tissue (ratio between median values = 5.6). The lead levels in hair and nails were of the same magnitude in the two groups. The workers showed positive correlations between lead concentrations in liver and kidney (Spearman's rho = rs = 0.59; p < 0.001), liver and hair (rs = 0.51; p = 0.003), liver and nails (rs = 0.52; p = 0.002) and hair and nails (rs = 0.52; p = 0.002). Lead concentrations in kidney correlated well with lead levels in hair (rs = 0.57; p = 0.001) and nails (rs = 0.51; p = 0.003), respectively. The positive correlation between the lead concentrations in liver and kidney indicates that these organs belong to the same soft tissue lead pool in the body. In retired lead workers, positive correlations were observed between the lead concentrations in liver and the cumulative blood lead index (CBLI) (rs = 0.50; p = 0.016), as well as between lead levels in kidney and CBLI (rs = 0.51; p = 0.014).

Aged↗
PubMed1994

Comparison of measures of lead exposure, dose, and chelatable lead burden after provocative chelation in organolead workers.

OBJECTIVES: To describe 6 h urinary lead excretion (6 h PbU) after 1 g intravenous ethylene diamine tetraacetic acid (EDTA) in organolead manufacturing workers with mixed exposure to organic and inorganic lead; to determine the predictors of lead excretion (PbU); and to determine the extent to which internal lead stores and ongoing external exposure govern blood concentrations of lead (PbB). METHODS: A case series of 21 active workers were studied. Personal industrial hygiene data, grouped by 29 exposure zones, in combination with personal interviews about work location and times were used to derive several measures of recent and cumulative exposure to organic and inorganic lead. The average exposure intensities assigned to the 29 zones ranged from 4 to 119 micrograms/m3 (0.02-0.57 mumol/m3 as lead) for organic lead and from 1 to 56 micrograms/m3 (0.004-0.27 mumol/m3) for inorganic lead. RESULTS: After controlling for age, 6 h PbU was significantly and positively correlated with summary measures of PbB--for example, lifetime peak PbB, time weighted PbB--and zinc protoporphyrin concentrations--for example, lifetime peak zinc protoporphyrin, time weighted zinc protoporphyrin--but not with measures of estimated external exposure--for example, duration of exposure and cumulative exposure to inorganic or organic lead. Among workers with higher chelatable lead burdens (6 h PbU > or = 212.4 micrograms (1.03 mumol) divided at the median), there was no apparent relation between recent inorganic lead exposure and PbB at the time of chelation. Among workers with lower chelatable lead burdens (6 h PbU < 212.4 micrograms (1.03 mumol) however, there was a significant relation between exposure and effect between recent exposure to inorganic lead and PbBs. CONCLUSION: These findings are consistent with the concept of physiological dampening. The high chelatable lead burden, a source of internal exposure, dampens the effect of external exposure on PbBs. The data suggest that in organolead workers with high chelatable lead burdens, PbBs may be more influenced by internal lead stores than by variations in airborne exposure to organic and inorganic lead.

Adult↗
PubMed1998

Determinants of bone and blood lead levels among teenagers living in urban areas with high lead exposure.

Although lead has been extensively studied in children, its sources and effects remain unclear in adolescents. This study examined the relation of blood and tibia bone lead levels to lead determinants. One hundred adolescents living in Mexico City and surrounding suburbs were studied. Blood lead was measured by atomic absorption spectroscopy, and tibia lead was measured by a K X-ray Fluorescence (KXRF) instrument. Blood lead ranged from 1.8 to 29.2 microgram/dl, with a mean of 7.4 microgram/dl. Bone lead ranged from <1 to 44.82 microgram Pb/g bone mineral, with a mean of 4.8 microgram Pb/g. Predictors of bone lead included higher traffic density near the home, mother's smoking history, and time spent outdoors. Predictors of log-transformed blood lead included bone lead levels, male sex, use of lead-glazed ceramics, and living in Mexico City. Bone lead remained a significant predictor of blood lead after adjusting for covariates in a final multivariate regression model. In our final model, a rise in bone lead from the middle of the lowest quintile to the middle of the highest quintile (a difference of 21.6 microgram Pb/g) was associated with an increase in blood lead of 1.2 microgram/dl. Our data suggest that in addition to current sources of environmental lead exposure, bone lead accumulated over time constitutes a moderate source of circulating lead during adolescence and may account for some of the adverse health effects documented in recent studies.

Adolescent↗
PubMed1996

Lead-contaminated house dust and urban children's blood lead levels.

OBJECTIVES: This study assessed the relationship between lead-contaminated house dust and urban children's blood lead levels. METHODS: A random-sample survey was used to identify and enroll 205 children, 12 to 31 months of age, who had resided in the same house since at least 6 months of age. Children's blood and household dust, water, soil, and paint were analyzed for lead, and interviews were conducted to ascertain risk factors for elevated blood lead (> or = 10 micrograms/dL). RESULTS: Children's mean blood lead level was 7.7 micrograms/dL. In addition to dust lead loading (micrograms of lead per square foot), independent predictors of children's blood lead were Black race, soil lead levels, ingestion of soil or dirt, lead content and condition of painted surfaces, and water lead levels. For dust lead standards of 5 micrograms/sq ft, 20 micrograms/sq ft, and 40 micrograms/sq ft on noncarpeted floors, the estimated percentages of children having blood lead levels at or above 10 micrograms/dL were 4%, 15%, and 20%, respectively, after adjusting for other significant covariates. CONCLUSIONS: Lead-contaminated house dust is a significant contributor to lead intake among urban children who have low-level elevations in blood lead. A substantial proportion of children may have blood lead levels of at least 10 micrograms/dL at dust lead levels considerably lower than current standards.

Black or African American↗
PubMed2001

Associations of lead biomarkers and delta-aminolevulinic acid dehydratase and vitamin D receptor genotypes with hematopoietic outcomes in Korean lead workers.

OBJECTIVES: This study compares and contrasts associations of dimercaptosuccinic acid (DMSA)-chelatable lead, tibia lead, and blood lead with five hematopoietic outcomes and evaluates the effect modification of these relations by polymorphisms in the delta-aminolevulinic acid dehydratase (ALAD) and vitamin D receptor (VDR) genes. METHODS: A cross-sectional study of 798 lead workers and 135 unexposed referents was performed. RESULTS: The DMSA-chelatable lead, tibia lead, and blood lead levels ranged in the lead (Pb) workers from 4.8 to 2103 g, -7 to 338 g Pb/g bone mineral, and 4 to 86 g/dl, respectively. The mean of the hemoglobin, hematocrit, zinc protoporphyrin (ZPP), and urinary (ALAU) and plasma (ALAP) delta-aminolevulinic acid levels of the lead workers were 14.2 (SD 1.4) g/dl, 42.4 (SD 4.4)%, 80.2 (SD 63.5) g/dl, 2.1 (SD 3.7) mg/l, and 17.7 (20.6) g/ml, respectively. After adjustment for the covariates, tibia lead was associated with all five hematopoietic outcomes, while blood lead and DMSA-chelatable lead were associated only with ZPP, ALAP, and ALAU. A comparison of the regression coefficients, total model adjusted R2 values, and delta R2 values revealed that blood lead was the best predictor of ZPP, ALAP, and ALAU. Only tibia lead was significantly associated with hemoglobin and hematocrit levels, but the additional variance explained by tibia lead was (<1%). No clear effect modification of the relations between the lead biomarkers and hematopoietic outcomes studied was caused by ALAD or VDR genotype. CONCLUSIONS: Lead must have a chronic, cumulative effect on hemoglobin and hematocrit levels, and any speculated mechanism cannot merely involve short-term plasma or target organ lead levels.

Adolescent↗
PubMed2002

The trends of changes in children's blood lead levels since the introduction of lead free gasoline in Shanghai.

OBJECTIVE: To describe trends of changes in blood lead levels in children aged 1 - 6 years during the time period before and after introducing lead free gasoline in Shanghai 1997 and 1999. METHODS: Blood lead levels of 1 969 children aged 1 - 6 years were determined by a sampling survey in five districts of Shanghai in August and September, 1997. Blood lead levels of the same population were re-determined by the same method from April to June in 1998 and from August to September in 1999. Filter paper blood lead test was carried out monthly using the filter paper blood lead proficiency testing program of Centers for Disease Control in the United States. The results from blood lead samples were under acceptable ranges during the study. RESULTS: The geometric means of blood lead levels were 83 microgram/L in 1997, 80 microgram/L in 1998 and 76 microgram/L in 1999, respectively. The prevalence rates of childhood lead poisoning (blood lead level was equal or more than 100 microgram/L) were 37.8% in 1997, 25.7% in 1998 and 24.8% in 1999. The amounts of decrease on average blood lead levels in the five districts between 1997 and 1999 were 10 microgram/L, 11 microgram/L, 6 microgram/L, 4 microgram/L and 2 microgram/L, respectively. CONCLUSION: Lead poisoning is a preventable disease. The average levels of lead in young children in Shanghai decreased significantly after the introduction of lead free gasoline to Shanghai. Lead emissions from vehicles running on leaded gasoline was one of the important contributors to increase the children's blood lead levels in Shanghai. Lead poisoning is not evenly distributed among children in Shanghai, resulting in the different levels of decline.

Child, Preschool↗
PubMedDate not supplied

An analysis of blood lead data in clinical records by external data on lead pipes and age of household.

This study examined the possibility that lead pipes in the drinking water distribution system were elevating the blood lead levels of children in London, Ontario, Canada. Based on their postal codes, 164 children admitted between 1984 and 1989 to an institution for the behaviorally disordered or developmentally challenged were categorized according to whether they lived in the area of the city known by the local Public Utilities Commission to be serviced by lead pipes. Analysis of covariance was used to obtain confounder-adjusted geometric means in each area. After adjusting for gender, year of lead test (a surrogate for gasoline source), and census tract prevalence of low family income, children in the lead service area (LSA) were found not to have higher blood lead levels (geometric means: LSA = 4.7 micrograms/dl, Non-LSA = 4.8 micrograms/dL; p = 0.839). The average blood lead level declined 60.9% between 1984 and 1989. Using municipal tax assessment data on the age of each child's home, those children living in homes built during or before 1945 (when interior paints were as much as 50% lead by dry weight) had an average blood lead level that was 62.3% higher (p = 0.011) than that of those in homes built since 1975 (when interior paints were limited to no higher than 0.5% lead by dry weight). A clear gradient was observed. This association with age of home remained significant after adjusting for gender, diagnosis, and year of lead test. Variables indicating the amount of industry near the child's residence and the presence of lead service pipes did not enter the model after house-age. In conclusion, no evidence indicated that the lead service pipes were elevating blood lead levels in these London children. The data suggest that with the removal of lead from gasoline, lead-based paint is a significant remaining source of lead exposure. Little data are available on childhood lead exposure from paint in Canada. The present descriptive data suggest that more research into this potential problem in Canada is warranted.

Adolescent↗
PubMed1975

Tetramethyl lead absorption: a report of human exposure to a high level of tetramethyl lead.

Accidental human exposure to a high level of tetramethyl lead is described. Tetramethyl lead is blended with petrol as an antiknock agent, and it has similar physical properties to tetraethyl lead. The patient had high levels of lead in urine, averaging 4-75 mumol (983 mug) daily for the first four days after exposure and he continued to have raised levels of urinary lead for six months. He had no symptoms or physical signs of lead poisoning and comparisons are made between this case and previously reported cases of poisoning by tetraethyl lead. In the cases of tetraethyl lead poisoning all the patients had symptoms, some severe, yet in no instance did the urinary lead levels approach those described in this patient. The effects of chelation therapy with calcium disodium versenate are discussed and the results are similar to those found in tetraethyl lead poisoning. Blood lead levels of up to 3-91 mumol/l (81 mug/100 g) occurred but these levels were not raised commensurate with the urinary lead output. The levels of deltaaminolaevulinic acid (ALA) in the urine were not significantly raised and this report shows that the urinary lead levels give a better guide to the degree of absorption of tetramethyl lead compared with the blood lead or urinary ALA levels. The report illustrates that tetramethyl lead is less toxic to man than tetraethyl lead.

Accidents, Occupational↗
PubMed1992

Nine-lead Holter monitoring using a lead-switching technique for the detection of ischemic ST changes.

We devised a technique to record a greater number of leads (a 9-lead monitor) by connecting a lead-switching adaptor to a commercially available 3-channel Holter recorder (9-lead DCG). Anodes were attached from positions V1 to V6 (CM1 to CM6), and to high lateral (HL), low lateral (LL) and low back (LB). A cathode was attached to the manubrium of the sternum. The CM5 lead was continuously recorded on channel 1. The device is able to switch continuously every 20 sec among leads CM6, LB, HL and LL on channel 2, and among leads CM1, CM4, CM2, and CM3 on channel 3. Electrocardiograms were simultaneously recorded with both the 9-lead DCG and the conventional 12-lead ECG systems during treadmill testing in 67 patients with coronary artery disease. In addition, 6 patients with acute myocardial infarction were studied with the 9-DCG to test ST elevation. The sensitivity and specificity of leads CM2 to CM6, HL, LL, and LB in detecting ST depressions that occurred in each corresponding lead of the 12-lead ECG lead were very high (p < 0.0001). The LB lead in particular was noteworthy for its markedly high specificity (94%) and sensitivity (83%) in detecting ST depressions occurring in leads II and aVF. Our lead-switching technique is useful when an increase in the number of leads is required in the DCG method. The LB lead, an anode on the low back, may be specific to detect inferior myocardial ischemia.

Adult↗
PubMed1999

Prevalence of elevated blood leads and exposure to lead in construction trades in Iowa and Illinois.

BACKGROUND: Despite lowering of the permissible exposure level for lead in construction from 200 to 50 microg/m3 in 1993, excessive lead exposure continues to be a problem. Relatively little data are available from the Midwestern U.S. on the environmental lead concentrations generated during various construction activities and the potential for worker exposure. This study characterized the prevalence of blood lead concentrations in high-risk construction trades in Iowa/Illinois, and identified risk factors for occupational exposure to lead in these construction workers. METHODS: A sample of 459 workers was selected from the total population of all union members from trade groups of painters, plumbers/pipefitters, ironworkers, laborers, and electricians. Participants completed an interviewer-administered questionnaire obtaining information on demographics, symptoms, occupational history, work practices, personal protective equipment, and training. Venous blood samples were collected from each participant and analyzed for blood lead (using atomic absorption spectroscopy) and free erythrocyte protoporphyrin levels. RESULTS: Blood lead levels (BLLs) of construction workers ranged from 0.1 to 50 microg/dL. Geometric mean blood lead concentrations by trade group were: laborers (7.6 microg/dL, n = 80); painters (5.9 microg/dL, n = 83); ironworkers (5.2 microg/dL, n = 87); plumbers (4.4 microg/dL, n = 82); electricians (2.4 microg/dL, n = 91). Blood lead levels for painters and laborers were significantly higher than other trade groups, and levels for electricians were significantly lower (p < 0. 01). Participants reported working primarily on commercial and industrial projects including new construction, renovation, and demolition. There were significant differences between the types of projects performed by different trade groups with laborers performing more highway/bridge renovation (p < 0.01), and plumbers reporting more residential remodeling (p = 0.05), repair of water lines containing lead (p = 0.04), or work on lead joints (p < 0.01). In addition to trade, elevated blood lead levels were associated with the type of construction project (especially bridge renovation and residential remodeling) and activities that include welding, cutting, rivet busting. The age of the home in which the worker lived, and hobbies such as casting/smelting lead for bullets or sinkers, were also important risk factors. Compliance with OSHA's Construction Lead Standard, and implementation of good occupational health and safety practices in general, was poor. CONCLUSIONS: Blood lead levels of 459 construction workers differed by the type of trade, type of project and specific job activity owing to differences in the inherent exposure potential of each task. Although the numbers of workers performing lead abatement projects were small, the trend for lower BLL in this group provides evidence that training, implementation of engineering controls, and proper use of personal protective equipment such as respirators is effective in controlling lead poisoning.

Adult↗
PubMed1998

The contribution of lead-contaminated house dust and residential soil to children's blood lead levels. A pooled analysis of 12 epidemiologic studies.

In 1992, the U.S. Congress passed the Residential Lead-Based Paint Hazard Reduction Act, which requires the promulgation of health-based dust lead and soil lead standards for residential dwellings to prevent undue lead exposure in children. Unfortunately, the levels of lead in house dust and soil that are associated with elevated blood lead levels among U.S. children remain poorly defined. This pooled analysis was done to estimate the contributions of lead-contaminated house dust and soil to children's blood lead levels. The results of this pooled analysis, the most comprehensive existing epidemiologic analysis of childhood lead exposure, confirm that lead-contaminated house dust is the major source of lead exposure for children. These analyses further demonstrate that a strong relationship between interior dust lead loading and children's blood lead levels persists at dust lead levels considerably below the U.S. Department of Housing and Urban Development's current postabatement standards and the Environmental Protection Agency's guidance levels. Finally, these analyses demonstrate that a child's age, race, mouthing behaviors, and study-site specific factors influence the predicted blood lead level at a given level of exposure. These data can be used to estimate the potential health impact of alternative health-based lead standards for residential sources of lead exposure.

Child, Preschool↗
PubMed2006

Lead isotopes and lead shot ingestion in the globally threatened marbled teal (Marmaronetta angustirostris) and white-headed duck (Oxyura leucocephala).

Lead isotope ratios ((206)Pb/(207)Pb and (208)Pb/(207)Pb) and concentrations in the livers and bones of marbled teal and white-headed duck found dead or moribund were determined in order to establish the main lead source in these waterfowl species. Lead concentrations in bone (dry weight) and liver (wet weight) were found to be very high in many of the white-headed ducks (bone: geometric mean=88.9 ppm, maximum=419 ppm; liver: geometric mean=16.8 ppm, maximum=57.0 ppm). Some of the marbled teal had high lead levels in the bones but liver lead levels were all low (bone: geometric mean=6.13 ppm, maximum=112 ppm; liver: geometric mean=0.581 ppm, maximum=4.77 ppm). Ingested lead shot were found in 71% of the white-headed duck and 20% of the marbled teal. The (206)Pb/(207)Pb ratio in livers and bones of white-headed ducks and marbled teals showed no significant differences compared to the ratios obtained from lead shot. The (206)Pb/(207)Pb ratio in bones of marbled teal ducklings with the highest lead concentrations tended to resemble the ratios of lead shot, which supports our hypothesis that the lead was derived from the hens. We also found that the lead ratios of lead shot and lead ratios described for soils in the area overlapped, but also that the isotopic ratio (206)Pb/(207)Pb in lead shot used in Spain has a narrow range compared with those used in North America. The principal source of lead in many of these birds was, however, most likely lead shot, as supported by the similar isotopic ratios, high lead concentrations in tissues and evidence of ingested shot.

Animals↗
PubMedDate not supplied

Low-level lead exposure and blood lead levels in children: a cross-sectional survey.

The authors studied 53 girls (44.5%) and 66 (55.5%) boys in Karachi, Pakistan, to determine their blood lead levels. The association between blood lead levels/water lead levels and the possible risk factors and symptoms associated with lead toxicity was explored. The mean lead level for the entire group was 7.9 microg/dl (standard deviation = 4.5 microg/dl). Thirty (25.2%) of the children had lead levels that exceeded 10 microg/dl; 12 (10.0%) of these had lead levels that exceeded 15 microg/dl. Thirteen (20.9%) of the children under the age of 6 yr (n = 62) had lead levels greater than 10 microg/dl, and 6 (9.6%) had levels in excess of 15 microg/dl. The authors found no association (p > .05) between high lead levels in water and blood lead levels in children. Mean blood lead levels were highest in the group of children exposed to various risk factors for lead absorption (e.g., exposure to paint, remodeling, and renovation; use of lead utensils; pica). There was a significant association between a history of exposure to paint/renovation activities and a history of pica. High blood lead levels in the children in Karachi stress the urgency for actions that control lead pollution. Screening programs should be instituted by the state. Individuals must become aware of lead's toxicity, and they must avoid substances that contain lead.

Age Factors↗