Average Blood Lead Concentration Research Articles

Exposure to environmental lead and visual-motor integration at age 7 years: the Port Pirie Cohort Study.

Early childhood exposure to environmental lead may result in subtle deficits in neuropsychological development. Most studies, however, have reported global measures of development, and the findings have not been consistent. In this report, we examine the association between blood lead concentration and a specific aspect of neuropsychological development, visual-motor integration. Each child in a cohort of 494 children living in and around the lead smelting town of Port Pirie, South Australia, was followed for its first 7 years of life. Serial blood samples were collected at various ages to estimate the lifetime burden of each individual. At the time of each blood sampling, systematic information was obtained on a wide range of other variables relevant to child development. We evaluated visual-motor integration at age 7 with the Beery Developmental Test of Visual-Motor Integration (mean score: 13.4). There was an inverse relation between blood lead concentration and visual-motor performance. After adjustment for potential confounding factors, both prenatal and postnatal blood lead concentrations exhibited a dose-related inverse association with children's visual-motor performance. For an increase in life-time average blood lead concentration from 10 micrograms per dl (0.48 mumol per liter) to 30 micrograms per dl (1.45 mumol per liter), the estimated deficit in children's visual-motor performance was 1.6 points (95% confidence interval = 0.3-2.9). The results indicate that visual-motor integration may be a more sensitive index than global measures of development, such as intelligence quotient, for the assessment of lead effects on child development.

Lead and cadmium concentrations in blood of people living near a copper smelter in Legnica, Poland

Examination of 60 inhabitants (including 28 children) of a village 900 m from a copper smelter with concurrent monitoring of air pollution was performed. Blood levels of lead and cadmium were measured three times in five years. At the same time dust amounts and air-dust concentrations of Cu, Pb, Cd, Mn, Cr, Zn, Ni and As were measured. In the first phase of the investigation, for nearly 60% of days Pb and Cu air concentrations exceeded 2–5 times the norm. In the third stage, after significant reductions of gas-dust emissions (copper from 992 to 47 tons/year, lead from 1720 to 30 tons/year) no excessive metal air concentrations are noted. In the first examination the average blood lead concentration was 0.766 ± 0.14 μg/ml (in the group of children 0.52 ± 0.07 μg/ml). After five years, there was a statistically significant decrease in the blood concentrations of lead, to 0.44 ± 0.14 μg/ml (children 0.31 ± 0.05 μg/ml), and cadmium, to 0.028 ± 0.007 μg/ml (children 0.019 ± 0.004 μg/ml). A big lead and cadmium load in the villagers, despite the substantial reduction of gas and dust emission, points to the contamination of the surroundings of the cooper smelter.

Short term prospective study of cognitive functioning in lead workers.

In a short term prospective study 70 male lead workers performed a series of cognitive tasks on three occasions during an eight month period. Concurrently with the cognitive testing, the concentrations of blood lead, zinc protoporphyrin (ZPP) and urinary aminolaevulinic acid (ALA) were measured. Indicators of lead absorption were stable during the study and each subject was allocated to either a low (below 20 micrograms/dl), medium (21-40 micrograms/dl), or high (41-80 micrograms/dl) group on the basis of their average blood lead concentrations. Performance deficits tended to be restricted to the high lead group and, in general, neither practice nor continued exposure during the study altered the magnitude of these deficits. The main deficit was a slowing of sensory motor reaction time, which was seen most clearly when the cognitive demands of the task were low. In the cognitively simple five choice task, blood lead concentration correlated with impaired decision making, response execution, and "lapses in concentration." In the other cognitive tasks the high blood lead group tended also to be slower by a factor of about 1.08 but the dominance of cognitive over sensory motor demands attenuated the exposure-performance correlations. The high lead group also had difficulty in recalling nouns poorly related to the focus of an earlier semantic classification task. This difficulty increased over time and was one of the few findings that correlated with all measures of lead absorption. It is concluded that the primary psychological profile of lead impairment is one of sensory motor slowing coupled with difficulties in remembering incidental information.

Serum Vitamin D Metabolites and Bone Mineralization in Young Children With Chronic Low to Moderate Lead Exposure

One hundred five children (49 male, 99 black) with known lead exposure indices from birth and adequate nutrient intake of calcium, phosphorus, and vitamin D were studied at 1 of 3 ages (21, 27, or 33 months) to determine the effects of chronic low to moderate lead exposure on circulating concentrations of vitamin D metabolites and bone mineral content as determined by photon absorptiometry. Univariate multiple regression analyses showed no direct relationship of blood lead levels to vitamin D metabolites or bone mineral content. Structural equation analyses which took into account potential covariates of age, season, race, and sex showed estimated declines in serum concentrations of total calcium (from 9.72 to 9.61 mg/dL), phosphorus (from 5.4 to 4.67 mg/dL), and 25-hydroxyvitamin D (from 27.24 to 25.8 ng/mL) and estimated increases in concentrations of parathyroid hormones (from 73.03 to 83.14 microL Eq/mL), 1,25-dihydroxyvitamin D (from 62.39 to 62.69 pg/mL), and bone mineral content (from 222.66 to 234.91 mg/cm) over the observed range of average lifetime blood lead concentrations (4.76 to 23.61 micrograms/dL, geometric mean 9.74 micrograms/dL). However, the only statistically significant effect of average lifetime blood lead concentration was that for phosphorus, and the multivariate test of the combined effects of lead on these six outcomes was not statistically significant (P = .2). It is concluded that significant alterations in vitamin D metabolism, calcium and phosphorus homeostasis, and bone mineral content are not present in children whose nutritional status is adequate and who experience low to moderate lead exposure.

Temporal and interindividual variation in erythrocyte zinc-protoporphyrin in lead exposed workers.

Nineteen male workers from a factory making lead batteries participated in monthly blood tests to follow the effects of decreasing exposures to lead. The overall average blood lead (B Pb) concentration was 1.95 mumol/l (40 micrograms/100 ml), but a significant decrease was seen over the one year study period. The relation to erythrocyte zinc-protoporphyrin (ZPP) concentration showed considerable scatter and only marginal improvement of the relation was obtained when each ZPP result was compared with the average B Pb concentration during the previous four months. On an individual basis, five men showed a considerable decline in ZPP following decreases in B Pb concentration. In five other subjects with similar decreases in B Pb, no change in ZPP concentration was seen. These two groups were similar with regard to haemoglobin concentration, initial B Pb concentration, and age, but differed in duration of exposure. A longer exposure time and presumably, therefore, larger body burdens of lead seemed to prevent the expected decrease in erythrocyte ZPP.

Dietary calcium and blood lead levels in women

Nutritional factors are known to influence metabolism and toxicity of several metals in animal experiments, but relevant human data are scarce and inconclusive. In this work, we tested the hypothesis that dietary calcium influences lead metabolism in humans. Blood lead concentrations were used as indicators of lead exposure and metabolism. Two groups of peasant women living in similar conditions in two different regions in Yugoslavia (100 in each) were chosen as subjects for this purpose. In region A, the dietary calcium intake was about 940 mg, and in region B about two times lower, i.e., 450 mg/day. The average blood lead concentration was significantly lower in women from region A (69 micrograms/L) than from region B (83 micrograms/L). Our results support the assumption that adequate calcium intake might be one of the preventive measures for decreasing lead absorption. This new evidence, sought for some time by nutritionists and toxicologists, needs further international confirmation.

Port Pirie Cohort Study: environmental exposure to lead and children's abilities at the age of four years.

We studied the effect of environmental exposure to lead on children's abilities at the age of four years in a cohort of 537 children born during 1979 to 1982 to women living in a community situated near a lead smelter. Samples for measuring blood lead levels were obtained from the mothers antenatally, at delivery from the mothers and umbilical cords, and at the ages of 6, 15, and 24 months and then annually from the children. Concurrently, the mothers were interviewed about personal, family, medical, and environmental factors. Maternal intelligence, the home environment, and the children's mental development (as evaluated with use of the McCarthy Scales of Children's Abilities) were formally assessed. The mean blood lead concentration varied from 0.44 mumol per liter in midpregnancy to a peak of 1.03 mumol per liter at the age of two years. The blood lead concentration at each age, particularly at two and three years, and the integrated postnatal average concentration were inversely related to development at the age of four. Multivariate analysis incorporating many factors in the children's lives indicated that the subjects with an average postnatal blood lead concentration of 1.50 mumol per liter had a general cognitive score 7.2 points lower (95 percent confidence interval, 0.3 to 13.2; mean score, 107.1) than those with an average concentration of 0.50 mumol per liter. Similar deficits occurred in the perceptual-performance and memory scores. Within the range of exposure studied, no threshold dose for an effect of lead was evident. We conclude that postnatal blood lead concentration is inversely related to cognitive development in children, although one must be circumspect in making causal inferences from studies of this relation, because of the difficulties in defining and controlling confounding effects.

UK Blood Lead Monitoring Programme 1984—1987: Protocol and Results For 1984

The Department of the Environment (DOE) has undertaken an extensive programme to monitor blood lead concentrations annually over the period 1984 to 1987 in the context of the reduction in the maximum permissible lead content of petrol from 0.4 to 0.15 g/l from 1st January 1986. The study includes adults living in heavily trafficked urban areas and in occupational groups particularly exposed to petrol lead; children aged 6-7 years attending schools in heavily trafficked urban areas; and control groups of adults and children in rural areas. The surveys are planned to cover about 1500 adults and 1000 children in total each year. Cohorts of adults are being followed, with replacement where necessary owing to moving, etc. For ethical reasons, no child will be sampled more than once, although the schools concerned will be revisited each year; children's blood is also being examined for antibodies to measles and poliomyelitis. Blood samples are being analysed for lead by atomic absorption spectrophotometry (AAS); considerable efforts are being made to ensure the validity of the analytical results during the period of the study. Results for 1984 indicated that average blood lead concentrations in both adults and children were generally low and were in line with levels expected on the basis of earlier surveys; only a very small proportion of individuals had raised levels. A detailed statistical analysis has confirmed the results of the EEC Blood Lead Surveys (carried out in 1979-1981) that blood lead concentrations were related to a range of personal, social and environmental factors including age, sex and smoking and drinking habits. Comparisons of any trends during the survey period in blood level concentrations in the exposed and control groups, together with results from the monitoring of sources of environmental lead should enable a broad assessment to be made of the effect of the reduction in petrol lead.

Lead exposure during demolition of a steel structure coated with lead-based paints. I. Environmental and biological monitoring.

Demolition of a steel railway bridge was carried out by nine workers using flame-torch cutting. The air in the breathing zone of the workers contained from 2 to 38 mg of lead/m3, which is a very high level in comparison with the Dutch exposure limit of 0.15 mg/m3 (8-h time-weighted average). Without very effective respiratory protection these concentrations may result in acute lead poisoning. Upwind of the flame-torch exposure the level was below the exposure limit, whereas downwind lead concentrations of up to ten times the exposure limit were observed. Although filtering facepieces were used by the workers, average blood lead concentrations of about 4.5 mumol/l were rapidly attained. Possibly under these work conditions this value represents a maximum concentration attainable in blood. After termination of the exposure, there was a fast decrease of lead in the blood. This finding indicates that lead was mainly present in rapidly exchangeable compartments like blood. No stable correlation between the concentration of lead in blood and the concentration of zinc protoporphyrin in blood was found.

Decreasing lead exposure in Swedish children, 1978–1984

Blood-lead levels were determined, each summer during the period 1978–1984, in children from Scania in Southern Sweden. A total of 1395 determinations were made. The average blood-lead concentration was 55 (range 14–250) μg l −1. There was a statistically significant decrease over time, both in rural and urban areas, averaging about 4 μg l −1 per year. Lead exposure has thus decreased remarkably. One possible explanation is the contemporary, considerable reduction of the alkyl lead content of petrol.

Decreased blood lead levels in residents of Stockholm for the period 1980-1984.

A number of measures have been taken to decrease the spread of lead to ambient air and food. In a study of the effect of these and other preventive measures, blood samples from approximately 100 persons living in the inner city area of Stockholm were collected and analyzed for lead content on three different occasions, in 1980, 1983, and 1984. The same subjects were examined on at least two occasions and the analytical method, atomic absorption spectrophotometry, was carefully controlled by means of reference samples on each occasion. The blood lead levels decreased during the observation period. The average blood lead concentrations for all the examined persons were 0.37, 0.26, and 0.25 mumol/l for 1980, 1983, and 1984, respectively. The mean of the differences in individual blood lead levels for 1980 and 1984 was 0.12 mumol/l. This figure corresponds to an average decrease in blood lead of 34% for all the subjects examined in 1980. The decrease occurred mainly during the period 1980-1983 (mean 0.11 mumol/l) and, thereafter, was only slight for the period 1983-1984 (mean 0.01 mumol/l). Factors such as age, sex, and change of residence during the observation period did not influence the final results.

Neuropsychological test results and symptoms among workers with well-defined long-term exposure to lead.

Lead intoxication is a classical environmental hazard that can cause encephalopathy. During recent years several studies have suggested poor performances in psychological tests and increased numbers of subjective symptoms among workers with comparatively low blood lead concentrations. Forty-nine long-term lead-exposed male workers with time-weighted average blood lead concentrations between 1.3 and 3.3 mumol/l calculated from at least seven years' results have been compared with a referent group of 27 male industrial workers with normal blood lead concentrations and comparable intellectual backgrounds. Several indices of exposure were used. Both groups were examined with neuropsychological tests and a questionnaire covering neuropsychiatric symptoms. The exposed group performed less well in 11 of 14 non-verbal tests, and there were significant differences in tests of memory and reaction time. A non-linear dose-effect trend was indicated. The results are in accordance with those found in similar studies, and it is concluded that the blood lead concentration should be below 2.5 mumol/l to avoid the effects shown in this study.

Effect of chemical composition and methods of preparation of complex oxide catalysts upon their physico-chemical and catalytic properties: Silica-zirconia catalysts

The average blood lead concentration has significantly decreased over the last two decades among the general population. However, in Belgium, there are still high-risk populations such as groups of pregnant women who have shown elevated lead levels. The objective of this study was to evaluate the current situation of lead cord blood levels and identify sources of lead exposure by a questionnaire survey. The study was conducted in 5 maternity units in Belgium; for each, umbilical cord blood samples were collected from 50 consecutive births. At the same time a questionnaire on possible sources of lead exposure was administered to the mother. The dependant variable was a dichotomous lead level variable (<20 μg/L vs. ≥20 μg/L). The factors associated with elevated lead levels (≥20 μg/L) were mother's country of origin from south Mediterranean and from Sub-Saharan Africa, mother's educational level, using ‘tagine’ plates for cooking and using khol for make-up, but, after adjusting for potential confounding factors, only the mother's country origin from south Mediterranean (adjusted odds ratio, 5.51; 95% confidence interval [CI], 1.68–18.08; p = 0.005) and from Sub-Saharan Africa (adjusted odds ratio, 8.14; 95% CI, 2.26–29.40; p = 0.001) were significantly associated with elevated cord blood lead concentrations (≥20 μg/L). The results of this study are similar to those found by a previous study in Belgium in 2004. Sources of exposure are difficult to distinguish with this questionnaire, which might be due to other important sources of exposure that were not included in the questionnaire. Confirmation of these risk factors in future studies could lead to new prevention strategies for populations who are at risk for subsequent lead exposure.