Herbert L. Needleman

Low-Level Environmental Lead Exposure and Children's Intellectual Function: An International Pooled Analysis

Lead is a confirmed neurotoxin, but questions remain about lead-associated intellectual deficits at blood lead levels < 10 μg/dL and whether lower exposures are, for a given change in exposure, associated with greater deficits. The objective of this study was to examine the association of intelligence test scores and blood lead concentration, especially for children who had maximal measured blood lead levels < 10 μg/dL. We examined data collected from 1,333 children who participated in seven international population-based longitudinal cohort studies, followed from birth or infancy until 5–10 years of age. The full-scale IQ score was the primary outcome measure. The geometric mean blood lead concentration of the children peaked at 17.8 μg/dL and declined to 9.4 μg/dL by 5–7 years of age; 244 (18%) children had a maximal blood lead concentration < 10 μg/dL, and 103 (8%) had a maximal blood lead concentration < 7.5 μg/dL. After adjustment for covariates, we found an inverse relationship between blood lead concentration and IQ score. Using a log-linear model, we found a 6.9 IQ point decrement [95% confidence interval (CI), 4.2–9.4] associated with an increase in concurrent blood lead levels from 2.4 to 30 μg/dL. The estimated IQ point decrements associated with an increase in blood lead from 2.4 to 10 μg/dL, 10 to 20 μg/dL, and 20 to 30 μg/dL were 3.9 (95% CI, 2.4–5.3), 1.9 (95% CI, 1.2–2.6), and 1.1 (95% CI, 0.7–1.5), respectively. For a given increase in blood lead, the lead-associated intellectual decrement for children with a maximal blood lead level < 7.5 μg/dL was significantly greater than that observed for those with a maximal blood lead level ≥7.5 μg/dL (p = 0.015). We conclude that environmental lead exposure in children who have maximal blood lead levels < 7.5 μg/dL is associated with intellectual deficits.

Bone lead levels in adjudicated delinquents: A case control study

BACKGROUND Lead exposure shares many risk factors with delinquent behavior, and bone lead levels are related to self-reports of delinquent acts. No data exist as to whether lead exposure is higher in arrested delinquents. The goal of this study is to evaluate the association between lead exposure, as reflected in bone lead levels, and adjudicated delinquency. METHODS This is a case-control study of 194 youths aged 12-18, arrested and adjudicated as delinquent by the Juvenile Court of Allegheny County, PA and 146 nondelinquent controls from high schools in the city of Pittsburgh. Bone lead was measured by K-line X-ray fluorescence (XRF) spectroscopy of tibia. Logistic regression was used to model the association between delinquent status and bone lead concentration. Covariates entered into the model were race, parent education and occupation, presence of two parental figures in the home, number of children in the home and neighborhood crime rate. Separate regression analyses were also conducted after stratification on race. RESULTS Cases had significantly higher mean concentrations of lead in their bones than controls (11.0+/-32.7 vs. 1.5+/-32.1 ppm). This was true for both Whites and African Americans. The unadjusted odds ratio for a lead level > or =25 vs. <25 ppm was 1.9 (95% CL: 1.1-3.2). After adjustment for covariates and interactions and removal of noninfluential covariates, adjudicated delinquents were four times more likely to have bone lead concentrations >25 ppm than controls (OR=4.0, 95% CL: 1.4-11.1). CONCLUSION Elevated body lead burdens, measured by bone lead concentrations, are associated with elevated risk for adjudicated delinquency.

Attentional Correlates of Dentin and Bone Lead Levels in Adolescents

In an effort to determine whether specific aspects of attention are impaired by lead, the performance of 79 subjects (aged 19 and 20 y) on a neuropsychologically based battery of tests of attention was examined in relation to lead levels in deciduous teeth (dentin), current blood, and tibia and patella bones measured by K-X-ray fluorescence. Dentin lead levels averaged 14 micrograms/g. Most bone lead levels were less than 10 micrograms/g. Dentin lead levels were related inversely to scores on two of four attention factors: focus-execute (ability to select and respond to critical information) and shift (ability to shift focus adaptively). Few significant associations were observed between bone lead levels and performance. Five individuals with the ALA-D 1-2 isozyme phenotype tended to achieve more optimal scores. Executive and self-regulation functions may be among the cognitive skills targeted by lead.

Sex ratio in offspring of patients with non-Hodgkin lymphoma.

To the Editor: In a letter in the November 5 issue, Alperovitch and Feingold reported an increased sex ratio (male:female) among children of women with multiple sclerosis.1 We have observed a remarkably decreased sex ratio in the offspring of young adults with non-Hodgkin lymphoma. We recorded the sex of the children of 197 patients with this disease who were participating in an epidemiologic study and obtained the same information from a control group of 240 patients without any evident malignant disease. Interviewing the control patients established that they had mainly cardiovascular or respiratory disorders. The results of this study are.

Low-level environmental lead exposure in childhood and adult intellectual function: a follow-up study

BackgroundEarly life lead exposure might be a risk factor for neurocognitive impairment in adulthood.ObjectivesWe sought to assess the relationship between early life environmental lead exposure and intellectual function in adulthood. We also attempted to identify which time period blood-lead concentrations are most predictive of adult outcome.MethodsWe recruited adults in the Boston area who had participated as newborns and young children in a prospective cohort study that examined the relationship between lead exposure and childhood intellectual function. IQ was measured using the Wechsler Abbreviated Scale of Intelligence (WASI). The association between lead concentrations and IQ scores was examined using linear regression.ResultsForty-three adults participated in neuropsychological testing. Childhood blood-lead concentration (mean of the blood-lead concentrations at ages 4 and 10 years) had the strongest relationship with Full-Scale IQ (β = -1.89 ± 0.70, p = 0.01). Full-scale IQ was also significantly related to blood-lead concentration at age 6 months (β = -1.66 ± 0.75, p = 0.03), 4 years (β = -0.90 ± 0.41, p = 0.03) and 10 years (β = -1.95 ± 0.80, p = 0.02). Adjusting for maternal IQ altered the significance of the regression coefficient.ConclusionsOur study suggests that lead exposure in childhood predicts intellectual functioning in young adulthood. Our results also suggest that school-age lead exposure may represent a period of increased susceptibility. Given the small sample size, however, the potentially confounding effects of maternal IQ cannot be excluded and should be evaluated in a larger study.

Subclinical lead exposure in philadelphia schoolchildren. Identification by dentine lead analysis.

Abstract Dentine lead levels were measured from shed deciduous teeth of 761 Philadelphia schoolchildren with no prior history of lead poisoning and residing in two school districts, one considered high risk for lead exposure, and one considered low risk. Black children in public schools from areas of deteriorated housing had marked elevations of dentine lead (mean of 198 μg per gram, in 174 children), with 20 per cent of the children having levels in the range associated with toxicity. White children from newer housing had the lowest levels (mean of 41.7μg per gram, 304 children), but a group of white children from intact housing living near and attending school adjacent to a major lead processor also had elevations of dentine lead (mean of 136 μg per gram, 71 determinations). Lead exposure as defined by dentine lead levels is more serious and widespread than previously acknowledged, and extends to groups other than those traditionally accepted as at risk. (N Engl J Med 290:245–248, 1974).

Environmental correlates of infant blood lead levels in Boston.

From a blood lead survey of 11,837 births, 249 newborns were enrolled in a 2-year, longitudinal study. Their blood leads (PbB) were measured semiannually, and their homes were visited for repeated collections of dust, soil, indoor air, tap water, and paint. Recent refinishing activity and the sizes of nearby streets were recorded. Overall mean PbB was 7.2 micrograms/dl (SD = 5.3) at birth. PbB did not vary systematically with age. Each subjects average postnatal PbB correlated highly with the amount of lead in dust (r = 0.4, P less than 0.0001) and soil (r = 0.3, P less than 0.001), and with the lead in paint (r = 0.2, P less than 0.01). Dust, soil and air lead levels correlated with one another. Refinishing activity in the presence of lead paint was associated with elevations of PbB. Water lead, proximate traffic, weight of recovered dust, race, maternal age and education, and sex were not predictive of PbB. Multivariate models of PbB were constructed that become increasingly predictive with age (r2 = 20 to 37%). Indoor dust lead, lead in soil, refinishing activity, and season were the independent variables.

Weight gain and maturity in fetuses exposed to low levels of lead

The relationship between prenatal low-level lead exposure and fetal growth was evaluated in a sample of 4354 pregnancies in which the mean umbilical cord blood lead level was 7.0 micrograms/dl (SD = 3.3; 10th percentile, 3.4 micrograms/dl, 90th percentile, 10.9 micrograms/dl). Higher cord blood lead levels were significantly associated with gestations of slightly longer duration. Comparing infants with cord blood lead levels greater than or equal to 15 micrograms/dl to those with levels less than 5 micrograms/dl, adjusted risk ratios of 1.5 to 2.5 were observed for low birth weight (less than 2500 g) and for fetal growth indices that express birth weight as a function of length of gestation (e.g., small-for-gestational age, intrauterine growth retardation). The 95% confidence intervals of these risk ratios included 1, however, precluding rejection of the null hypothesis of no association. We conclude that the risk of adverse fetal growth is not increased at cord blood lead levels less than 15 micrograms/dl but that modest increases in risk may be associated with levels greater than or equal to 15 micrograms/dl.

Low level lead exposure: history and discovery.

The history of lead toxicity spans 2 millennnia. With increasingly sensitive methods, deficits due to lead exposure have been demonstrated at lower and lower doses. Persuasive evidence suggests that no threshold for lead toxicity exists.

The lead content of human deciduous and permanent teeth.

Abstract The distribution of lead in human permanent and primary teeth was determined. Comparable levels of lead were found in coronal dentine, root dentine, and enamel. However, in secondary dentine the lead level was elevated. By reaming, this elevation was shown to be greatest in the most superficial layers of this zone. Secondary dentine is in intimate contact with blood and its elevated lead content probably reflects its actual exposure to lead throughout the life of the tooth. It is suggested that this tissue could be of value in the diagnosis of plumbism.