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EnvironHealthPerspect113(7):894-899 (2005); https://doi.org/10.1289/ehp.7688 The source of the errors in this article, which were limited to the Boston cohort, was twofold. Specifically, performance IQ data were used instead of full-scale IQ [...]

BACKGROUND; Animal studies suggest that early-life lead exposure influences gene expression and production of proteins associated with Alzheimer's disease (AD). OBJECTIVES: We attempted to assess the relationship between early-life lead [...]

According to the U.S. Public Health Service, lead poisoning remains the most common and societally devastating environmental disease of young children. About 16 percent all American children have blood lead levels in the neurotoxic range. Being poor dramatically increases this risk. The lead industry has long camouflaged lead's toxicity. Department of Housing and Urban Development reforms are ineffectual. (MLH)

Discusses the mounting evidence for the neurological damage of childhood lead poisoning. Argues that ignoring lead poisoning is more expensive than preventing it. Reviews a recent plan to eradicate lead poisoning and the sociological factors that may impede its implementation. (CJS)

Lead exposure may predispose young children to antisocial behavior and delinquency. Researchers asked the parents and teachers of 301 grade-school boys to rate the child's behavior at the age of 7 and 11 using questionnaires that measure antisocial tendencies. The boys were also asked to rate themselves. X-ray fluorescence was used to measure the lead concentration in the boy's bones at the age of 11. Compared to boys with low lead levels, boys with high lead levels were rated by their parents and teachers as more aggressive and as having other problems such as health complaints, attention problems and delinquent behavior. The boys with high lead levels rated themselves as having more behavioral problems. Parents and teachers reported that behavioural problems in boys with high lead levels had gotten worse between the ages of 7 and 11. The association between high lead levels and antisocial behavior remained when the data were adjusted for other social and family factors.

Several studies suggest that prenatal or infantile exposure to lead is associated with slower mental development, and that this occurs at levels that are lower than currently recognized as unsafe or elevated. However, the relationship between such early subclinical exposures and subsequent performance at preschool and school ages has not been established. The effect of lead exposure on cognitive (intellectual) development was evaluated in a group of 170 middle-class and upper-middle class children for approximately five years. Differences in blood lead levels measured at birth, an indicator of prenatal exposure, were not related to subsequent cognitive performance. However, elevated blood lead levels at 24 months significantly correlated with lower cognitive performance at 57 months of age; this was independent of social factors. Analysis showed that children with high levels of prenatal exposure 'recovered' better if postnatal lead exposure was low. Males improved less than females, and social factors such as class and maternal IQ also affected recovery. Deficits were most apparent in measures of visual-spatial and visual-motor integration skills. The results indicate that among socially advantaged children, prenatal exposure to lead or to low lead levels during early infancy may be overcome if lead exposure subsequently decreases. However, this likely represents optimum conditions; children with fewer advantages or those with greater or later lead exposure will probably have more cognitive development problems. (Consumer Summary produced by Reliance Medical Information, Inc.)

Lead in high doses is clearly toxic to the human nervous system. While scientists have suspected that low-level exposure to lead affects the intelligence quotients (IQ) of children, this relationship has been difficult to study for various reasons and has not yet been firmly established. A statistical technique called meta-analysis was used to integrate the results of 12 studies that were conducted independently by different researchers. All 12 studies examined the correlation between lead levels in the blood or teeth and IQ, while attempting to control for factors other than lead that might also influence IQ. The number of children participating in each study ranged from 75 to 724. Results of meta-analysis strongly supported the theory that low-level lead exposure has an adverse effect on IQ in children, since lead level and IQ score were inversely related to a very significant degree. While it cannot be proven that low-level lead exposure causes intellectual deficits, there is much evidence to suggest that the relationship is one of cause and effect. Causation is supported by the following findings. Many studies conducted under different conditions have drawn the same conclusion, and other possible causes of low IQ have been effectively eliminated; in addition, it is logical that lead would depress intelligence, given the physiological effects of this metal on the nervous system. (Consumer Summary produced by Reliance Medical Information, Inc.)

Relatively few studies have been performed on the long-term effects of exposure to low levels of lead in childhood. Exposure to lead, a heavy metal, may result in serious central nervous system damage in infants and children. The toxic effects of lead exposure in childhood had been studied previously in a group of 270 young school children from 1975 to 1978. Although the subjects did not suffer from plumbism (lead poisoning) they did have abnormally high levels of lead that were detected in their teeth (dentin lead). The results of this earlier study revealed that these children had low IQ scores, poor classroom performance, and speech, language and attention problems. A follow-up study was performed with 132 individuals from this original group. These subjects, now young adults, were re-examined in 1988 to evaluate the long-term effects of their earlier lead exposure. In general, the findings from the subjects' earlier tests, which included cognitive impairment and retarded academic progress, persisted into adolescence. Young adults who had higher dentin lead levels as children were seven times more likely to drop out of high school and had lower class standings, weaker reading skills, greater absenteeism, and more impairment of motor skills such as hand-eye coordination. The authors pointed out that there was some level of selection bias in this study; individuals who were retested tended to be those with lower lead levels in childhood. Those with the highest lead concentrations, lowest socioeconomic status, and lowest IQs could not be located for follow-up. Therefore, the estimates made concerning the extent of damage from early lead exposure are conservative and actual effects may have been even more detrimental. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abstract Background Early life lead exposure might be a risk factor for neurocognitive impairment in adulthood. Objectives We 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. Methods We 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. Results Forty-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. Conclusions Our 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.

Opposing views regarding the connection between lead exposure and cognitive impairment are presented. C. B. Ernhart states that no study has yet proved that low-level lead exposure is detrimental to child development, while H. L. Needleman asserts that previous research studies have proven conclusively that such a connection exists. (CB)