Low-level lead exposure in childhood influences neuropsychological performance

Cumulative lead exposure in 193 inner-city black children was assessed by measuring lead concentrations in the primary and circumpulpal dentine of their deciduous teeth. Lead concentrations for these children were comparable to the concentrations reported in population studies of low-income children living in inner-city areas. Analysis of the children's neuropsychological test performance showed that elevated lead levels were associated with deficits in visual-motor functioning and perceptual integration, right-left orientation, and verbal abstraction; other verbal abilities and motor functioning were not affected. Possible alternative explanations for these findings were evaluated by examining the relationships between lead and maternal intelligence, family socioeconomic status, and perinatal indicators of neurological impairment. None of these relationships was significant. It was concluded that, even at levels usually regarded as asymptomatic, lead in the environment represents a hazard to inner-city children.     

The relationship between early childhood blood lead levels and performance on end-of-grade tests

BACKGROUND: Childhood lead poisoning remains a critical environmental health concern. Low-level lead exposure has been linked to decreased performance on standardized IQ tests for school-aged children. OBJECTIVE: In this study we sought to determine whether blood lead levels in early childhood are related to educational achievement in early elementary school as measured by performance on end-of-grade (EOG) testing. METHODS: Educational testing data for 4th-grade students from the 2000-2004 North Carolina Education Research Data Center were linked to blood lead surveillance data for seven counties in North Carolina and then analyzed using exploratory and multivariate statistical methods. RESULTS: The discernible impact of blood lead levels on EOG testing is demonstrated for early childhood blood lead levels as low as 2 microg/dL. A blood lead level of 5 microg/dL is associated with a decline in EOG reading (and mathematics) scores that is roughly equal to 15% (14%) of the interquartile range, and this impact is very significant in comparison with the effects of covariates typically considered profoundly influential on educational outcomes. Early childhood lead exposures appear to have more impact on performance on the reading than on the mathematics portions of the tests. CONCLUSIONS: Our emphasis on population-level analyses of children who are roughly the same age linked to previous (rather than contemporaneous) blood lead levels using achievement (rather than aptitude) outcome complements the important work in this area by previous researchers. Our results suggest that the relationship between blood lead levels and cognitive outcomes are robust across outcome measures and at low levels of lead exposure.     

Relation of cumulative exposure to inorganic lead and neuropsychological test performance.

OBJECTIVES--To determine if measures reflecting chronic occupational lead exposure are associated with performance on neuropsychological tests. METHOD--467 Canadian male lead smelter workers (mean (SD) age 43.4 (11.00) years, education 9.8 (3.18) years, years of employment 17.7 (7.43), and current blood lead concentration (B-Pb) 27.5 (8.4) micrograms dl-1) were given a neuropsychological screening battery. Time weighted average (TWA) and time integrated blood levels (IBL) were developed from B-Pb records obtained through regular medical monitoring (mean (range) TWA 40.1 (4.0-66.4) micrograms dl-1, mean IBL 765.2 (0.6-1625.7) micrograms-y dl-1). 14 neuropsychological variables were included in three multivariate analyses of covariance, with each exposure variable as the grouping variable (high, medium, and low) and age, education, score on a measure of depressive symptoms, and self reported alcohol use as the covariates. Groups did not differ in history of neurological conditions. RESULTS--Neither the B-Pb, TWA, nor IBL was significant by multivariate analyses of covariance (MANCOVA). When years of employment, a suppressor variable, was included as a covariate, IBL exposure groups differed significantly on digit symbol, logical memory, Purdue dominant hand, and trails A and B. CONCLUSIONS--A dose-effect relation was found between cumulative exposure (IBL) and neuropsychological performance at a time when current B-Pb concentrations were low and showed no association with performance.     

Impact of lead transport on children's blood and environmental lead levels

Introduction: A lead monitoring project was established in 1996 to monitor the environmental and health effects of lead being transported through a remote town in tarpaulin‐covered trucks. Methods: Dust samples from sites on the transport route were collected at 3–6 monthly intervals between 1996 and 1999. Annual blood lead testing clinics, offering voluntary testing to children, were conducted from 1997 to 1999. Results: Of the 55 dust samples analysed, only nine contained particles of lead concentrate and these were present at very low levels. During the project 167 children were tested. The geometic mean of blood lead levels in 1997, 1998 and 1999 were 4.5 μg/dL, 5.0 μg/dL and 5.1 μg/dL, respectively (all within the normal range). Residence on the transport route was not associated with higher lead levels (P > 0.05). Conclusions: Lead transport was not associated with any detectable environmental contamination or increase in children's blood lead levels.     

Prediction of children's blood lead levels on the basis of household-specific soil lead levels

To help guide policy decisions about removing lead-contaminated soils, the authors estimated a regression model for predicting a child's blood lead level on the basis of his or her household-specific soil lead level. The data analyzed were blood lead levels (1-45 micrograms/dl) and household-specific soil lead levels (53-20,700 ppm) of 596 children aged 1-5 years who lived in the Helena Valley of Montana and the Silver Valley of Idaho during August 1983. A non-threshold, multiple linear regression model indicated that the estimated mean natural log transformed blood lead level increased by 0.231 micrograms/dl for each unit increase in natural log transformed soil lead level (ppm), after adjusting for the average number of daily outdoor play hours and whether someone in the household smoked. The model predicted that, at a soil lead level of 1,000 ppm, a child who does not play outside and who does not live in a household where someone smokes would be at low risk of lead toxicity (blood lead level between 4 and 24 micrograms/dl).     

An investigation of dust lead sampling locations and children's blood lead levels

The objective of this study is to provide guidance on where to collect dust lead wipe samples in homes to best characterize the risk of a resident child having a blood lead level at or above the CDC level of concern (10 microg/dl). In 1998, the Milwaukee Health Department enrolled 72 children living in pre-1950 buildings: 34 had elevated (i.e., > or = 10 microg/dl) blood lead levels (EBL); and 38 had non-elevated blood lead levels (non-EBL). This study explored dust lead sampling locations by examining loading differences between homes where children with EBL and non-EBL lived. Floor, windowsill, and window trough samples were collected in the living room, kitchen, bathroom, and child's bedroom and play area. Floor samples were collected at four locations: room entry; center of the room; under a window; and against the wall opposite the window (perimeter). Geometric mean floor dust lead levels were generally two to three times higher in homes of EBL children than homes of non-EBL children. Sampling the floor at the room entry or center is preferable to sampling under the window or from the perimeter of the room. When the central floor average was used, the room combinations that had the greatest differences between homes of EBL children and non-EBL children all included a sample from the child's bedroom and excluded the bathroom. When the entry floor average was used, the greatest differences also excluded bathrooms, but otherwise included a mix of all of the other rooms. Window samples did not distinguish where children with EBLs versus non-EBLs resided. This paper is based on Milwaukee alone, so generalizing results to other locations should be done with caution.     

Correlation between maternal and cord blood lead levels

Whole blood lead levels were estimated by atomic absorption analysis in 226 blood samples from 113 mothers of 23 different nationalities. Samples were collected before delivery, and from cord blood from their respective neonates. The concentrations of blood lead were within the expected range of occupationally unexposed populations. Mean maternal blood lead levels were 0.72 0.10 mumol/l (14.9 2.14 mug/dl), range 0.32-1.34 mumol/l (6.6-27.8 mug/dl) and mean cord blood levels were 0.64 0.12 mumol/l (range 0.29-1.46 mumol/l). Sixteen percent of the mothers and nearly 10% cord blood samples were found to have blood lead level greater than 0.97 mumol/l (20 mug/dl). Very high levels, in excess of 1.21 mumol/l (25 mug/dl), were detected in 3.5% of mothers as compared to 2.6% of cord blood samples. Out of 113 infants, 65 (58%) were males with a mean cord blood lead level of 0.63 mumol/l and 48 (42%) were females with a mean level of 0.66 muol/l. The lowest maternal blood lead levels 0.68 mumol/l were observed in ages 20 to 25 years old, and lowest cord blood levels 0.58 mumol/l were seen in maternal age of less than 20 years old. On the other hand, the highest maternal and cord blood lead levels (0.82 and 0.75 mumol/l, respectively) were observed in maternal ages of greater than 35 years old. The results show a direct correlation of blood lead level between mothers and umbilical cord as seen in the linear regression distribution curve.     

产妇及新生儿血铅水平调查

目的:了解佛山市产妇、新生儿血铅水平及其影响因素。方法:采用电感耦合高频等离子体发射光谱法,于2003年6月～2004年2月,取本院产科产妇静脉血及其新生儿脐血588例,进行血铅、钙、锌、铁、铜和锰水平测定,按妇幼保健管理卡内容,进行相关记录。结果:产妇血铅水平0.424±0.170μmol/L,Bpb≥0.483μmol/L者占19.05％,新生儿脐血铅水平0.417±0.164μmol/L,铅中毒率为18.71％;母子血铅值显著正相关(r=0.861,P<0.01),产妇血铅值与其血钙、铁值显著负相关(r=-0.267、-0.298,P<0.05);城郊产妇及新生儿血铅水平显著高于城区。结论:城郊产妇、新生儿血铅较高,血钙、锌、铁含量影响血铅水平。     

Recent trends in childhood blood lead levels

Blood lead levels in children in the United States have declined through 1994, the date of the most recent National Health and Nutrition Examination Survey. In this investigation, the authors analyzed whether blood lead levels have changed since 1994 and quantified the magnitude of any change. The authors evaluated blood lead levels from 12 longitudinal data sets from 11 states and 1 city. Geometric mean blood lead levels declined between 4%/year and 14%/year in 8 of the data sets. No differences in decline rates were observed between data sets from states that had universal screening as a goal or that included repeat measures for an individual child and those data sets that did not. The authors' best estimate for these populations was a decline rate of 4-7%/year, which was comparable to the decline rate prior to 1994.     

Home refinishing, lead paint, and infant blood lead levels.

We measured the blood lead levels of 249 infants semi-annually from birth to two years of age; we sampled the home paint and recorded any recent home refinishing activity. Mean blood lead from birth to age 2 years did not vary systematically with age but did correlate significantly with the amount of lead in the indoor paint (p less than .01). Refinishing activity in homes with high lead paint was associated with elevations of blood lead averaging 69 per cent.     

Relationship between blood lead levels and renal function in lead battery workers

OBJECTIVES: The aim of this study was to investigate the correlation between blood lead (PbB) levels and renal function indices of blood-urea nitrogen (BUN), serum creatinine (SC) and uric acid (UA) among lead battery workers with exposure to lead. METHODS: A total of 229 workers of both genders from two lead battery factories were recruited in this cross-sectional study. The personal airborne and blood samples were collected on the same day. The airborne lead (PbA) and PbB levels, and individual renal function parameters were measured and statistically analyzed. RESULTS: A positive correlation between PbB levels and individual renal function index of BUN, SC, and UA was found ( P<0.01). The PbB levels and renal function indices showed significant difference between male and female workers. Based on a multiple regression model, an increment of 10 micro g/dl PbB produced an increase of 0.62 mg/dl BUN, after being adjusted for work duration and age, and an increase of 0.085 mg/dl UA, after being adjusted for gender and body weight. Workers with PbB 60 microg/dl showed a positive dose-effect relationship with significant difference in BUN ( P<0.001) and UA ( P<0.05), and the percentage of workers with BUN and UA over the reference value also showed an increasing trend. CONCLUSION: Blood-urea nitrogen and uric acid could be considered as suitable prognostic indicators of renal dysfunction in lead-exposed workers. Our results showed that PbB levels higher than 60 micro g/dl had increasing chances of inducing adverse renal effects.     

产妇及新生儿血铅水平调查

目的了解佛山市产妇、新生儿血铅水平及其影响因素.方法采用电感耦合高频等离子体发射光谱法,于2003年6月～2004年2月,取本院产科产妇静脉血及其新生儿脐血588例,进行血铅、钙、锌、铁、铜和锰水平测定,按妇幼保健管理卡内容,进行相关记录.结果产妇血铅水平0.424±0.170 μmol/L,Bpb≥0.483 μmol/L者占19.05%,新生儿脐血铅水平0.41 7±0.164μmol/L,铅中毒率为18.71%;母子血铅值显著正相关(r=0.861,P＜0.01),产妇血铅值与其血钙、铁值显著负相关(r=-0.267、-0.298,P＜0.05);城郊产妇及新生儿血铅水平显著高于城区.结论城郊产妇、新生儿血铅较高,血钙、锌、铁含量影响血铅水平.     

Correlates of bone and blood lead levels in carpenters

In the course of a health screening for construction carpenters, 127 subjects underwent blood lead testing, administration of detailed questionnaires, and in vivo measurement of bone lead levels with a ¹⁰⁹Cd K-X-ray fluorescence (K-XRF) instrument. The mean age of subjects was 48.5 (SD = 9.8) years. Blood lead levels were low, with a mean of 8.2 (SD = 4.0) μg/dl. Bone lead levels had means of 9.8 (SD = 9.3) μg/g bone mineral for the tibia and 14.0 (SD = 13.8) μg/g bone mineral for the patella (which consist primarily of cortical bone and trabecular bone, respectively). In multivariate regression models, age was the dominant predictor of both tibia and patella bone lead, with years since last worked and welding/brazing contributing an additional small amount of influence over tibia bone lead, and carpet laying, paint stripping, and regular exercise contributing an additional small amount of influence over patella bone lead. Demolition, carpet laying, and alcohol ingestion were significant predictors of blood lead. We conclude that age is the most important predictor of bone lead levels among workers with intermittent exposures to lead; in addition, K-XRF is useful in generating hypotheses on additional factors that may influence lead burden.     

Umbilical cord blood lead levels in California

During the fall of 1984, we conducted a survey of umbilical cord blood lead levels of 723 live births that occurred at 5 hospitals located in 5 cities in California. Historical ambient air lead levels were used as a qualitative surrogate of air and dust exposure. The area-specific cord blood means (all means approximately 5 micrograms/dl), medians, deciles, and distributions did not vary among locations. The California distributions included means that were lower than the 6.6 micrograms/dl reported in Needleman et al.'s Boston study in 1979. Indeed, the entire California distribution was shifted to the left of the Boston study distribution, even though 3% of the California cord lead levels exceeded 10 micrograms/dl--the level above which Needleman et al. have documented psychoneurological effects in children during the first few years of life. Fourteen percent of premature babies had cord blood lead levels above 10 micrograms/dl. The association between prematurity (i.e., less than 260 d gestation) and elevated (greater than 5 micrograms/dl) cord blood lead was observed in all hospitals and yielded a relative risk of 2.9 (95% CI: .9, 9.2) and a population attributable risk of 47%. Further research is needed to confirm this association and to explore the roles of endogenous and exogenous sources of lead exposure to the mothers who give birth to premature infants.     

High blood lead levels in recreational indoor-shooters

Introduction  Recreational shooting in indoor firing ranges is very popular in Germany. Lead-containing ammunition is still in use. Therefore we checked the blood lead levels (BLL) from 129 subjects doing several types of shooting disciplines. Methods  In total, BLLs of 129 shooters (nine female) from 11 different shooting ranges with a mean age of 49 years were measured. The blood samples were taken after the volunteers had given written informed consent. Determination of lead was carried out by graphite furnace atomic absorption (GF-AAS) under strict internal and external quality control schemes. Results  While individuals shooting only with airguns (n = 20) showed a median BLL of 33 μg/l (range 18–127 μg/l), those who were also users of .22 lr weapons (n = 15) turned out to have a median of 87 μg/l (range 14–172 μg/l). Shooters of .22 lr and large calibre handguns (9 mm or larger) (n = 51) had median 107 μg/l (range 27–375 μg/l) and those only using large calibre handguns (n = 32) had median 100 μg/l (range 28–326 μg/l). The IPSC-group (n = 11) had the highest median with 192 μg/l (range 32–521 μg/l). Conclusion  Our results show clearly that many shooters have high blood levels; some of them are still exceeding threshold limit values (TLVs) for lead exposed workers. Especially for younger women there is a high potential risk if they become pregnant. So there is a clear need for improving the situation whether by use of lead-free ammunition or by better ventilation systems.     

Declining blood lead levels in Victorian children

Abstract: To investigate the distribution of blood lead levels in a sample of Victorian children, and to compare current levels with those from a similar survey in 1979, blood was tested for lead in 252 children (123 under five years) attending Royal Children's Hospital as outpatients and having venepuncture blood samples for medical reasons. Blood lead levels were determined by graphite furnace atomic absorption spectrophotometer. The mean blood lead level was 0.26 μmol/L (5.4 μg/dL). In the under-five age group, the mean was 0.28 μmol/L (5.7 μg/dL). Only 1.6 per cent of this group exceeded the National Health and Medical Research Council action level of 0.72 μmol/L (15 μg/dL). Levels in this age group have declined significantly since 1979, when the mean was 0.54 μmol/L (11.1 μg/dL) and 12.9 per cent exceeded 0.72 μmol/L (15 μg/dL). Average blood lead levels have halved since 1979, with likely contributing factors being reduced exposure from lead in diet, reduced access to lead in paint and reduced lead in ambient air. Children with elevated levels had identifiable risk factors such as pica or exposure to lead-based paint, suggesting the need for ongoing public health action to prevent exposure in these groups.     

Prenatal lead blood levels in a city heavily exposed to lead

The blood lead concentrations were measured in 38 pregnant women and their newborn babies in a high exposure area. The lead content of human milk was also determined on the 5th day after delivery. The blood lead concentrations were higher than 12 micrograms/100 ml in more than 80 per cent of the samples. The lead content of breast milk was also greater than those of published recently. We found a strong correlation between the blood lead levels of the mothers and the newborns. There was a moderate correlation between the lead concentrations in the blood and the breast milk.