Developmental lead exposure and adult criminal behavior: A 30-year prospective birth cohort study.

Using a variety of research designs and measures of lead absorption, numerous studies link childhood lead exposure to a range of cognitive and behavioral deficits, including low IQ, impulsivity, juvenile delinquency, and criminal behavior in adolescence and early adulthood. In this study, we tested the association between multiple measures of blood lead concentration assessed in childhood with criminal behavior in adulthood and across the life-course. Prospective data from the Cincinnati Lead Study (CLS) included blood lead measures quarterly across the first 78 months of life and the number of times a person was arrested across the life-course (from age 18 to 33 years) and in later adulthood (age 27 to 33 years). Childhood blood lead concentration prospectively predicted variation in adult arrests and arrests over the life-course, indicating lead absorption is implicated in the etiology of crime-especially in geographic areas where environmental sources of lead are more prevalent and concentrated. Efforts to decrease lead exposure in both developed and developing countries should be part of a comprehensive strategy to reduce social dislocation and crime.

Lead in a case of encephalopathy.

A 2-year-old boy with a history of pica was admitted with vomiting and treated overnight for viral tonsillitis. A week later, he presented with a prolonged afebrile seizure and required intubation and ventilation. Antibiotics and acyclovir were started. Despite extensive investigations including MRI head, no cause was identified. Four days later, he deteriorated with signs of raised intracranial pressure. On day 5, blood lead concentration in the sample collected at admission was reported as grossly elevated, consistent with a diagnosis of severe lead poisoning from ingesting lead-containing paint at the family home. Chelation therapy was started but, unfortunately, he did not make a neurological recovery, and care was withdrawn. A serious case review identified a lack of awareness of lead poisoning and its relation to pica as a root cause. We report this case to share our experience and the importance of considering lead poisoning in children with pica.

Research Review: Environmental exposures, neurodevelopment, and child mental health - new paradigms for the study of brain and behavioral effects.

BACKGROUND: Environmental exposures play a critical role in the genesis of some child mental health problems. METHODS: We open with a discussion of children's vulnerability to neurotoxic substances, changes in the distribution of toxic exposures, and cooccurrence of social and physical exposures. We address trends in prevalence of mental health disorders, and approaches to the definition of disorders that are sensitive to the subtle effects of toxic exposures. We suggest broadening outcomes to include dimensional measures of autism spectrum disorders, attention-deficit hyperactivity disorder, and child learning capacity, as well as direct assessment of brain function. FINDINGS: We consider the impact of two important exposures on children's mental health: lead and pesticides. We argue that longitudinal research designs may capture the cascading effects of exposures across biological systems and the full-range of neuropsychological endpoints. Neuroimaging is a valuable tool for observing brain maturation under varying environmental conditions. A dimensional approach to measurement may be sensitive to subtle subclinical toxic effects, permitting the development of exposure-related profiles and testing of complex functional relationships between brain and behavior. Questions about the neurotoxic effects of chemicals become more pressing when viewed through the lens of environmental justice. CONCLUSIONS: Reduction in the burden of child mental health disorders will require longitudinal study of neurotoxic exposures, incorporating dimensional approaches to outcome assessment, and measures of brain function. Research that seeks to identify links between toxic exposures and mental health outcomes has enormous public health and societal value.

Avaliação do desempenho escolar de crianças contaminadas por chumbo / Academic performance evaluation of lead-poisoned children / Evaluación del desempeño escolar de niños contaminadas por plomo

A contaminação de crianças por chumbo tem sido objeto de investigação no âmbito da saúde pública. Neste estudo avaliou-se o desempenho acadêmico de 102 crianças do Ensino Fundamental. Os participantes foram divididos em dois grupos: um com 34 crianças não contaminadas ou com nível inferior a 5 μg/dl e o outro, de 68 crianças, estava com nível de contaminação por chumbo no sangue entre 10 and 40 μg/dl. Para avaliação foram utilizados o Teste de Desempenho Escolar (TDE) e anamnese. Os resultados indicaram melhor desempenho acadêmico para o segundo grupo, com diferenças significantes em aritmética, leitura e desempenho geral. A comparação entre os sexos indicou melhor desempenho para meninas, dado coerente com a percepção dos pais na anamnese. Embora outras variáveis estejam presentes, os dados apontam prejuízos acadêmicos maiores para crianças com índices de chumbo mais altos. Esses achados requerem políticas públicas para controle da contaminação e redução dos danos em contaminados.(AU)

The lead contamination in children has been the subject of research in the field of public health. This study evaluated the academic performance of 102 children from first to fourth grade. The subjects were divided into two groups. The first group was composed of 34 children without lead poisoning or with poison at levels lower than 5 μg/dl. The second group was composed of 68 children with blood lead levels between 10 and 40 μg/dl. The instruments used to evaluate the academic performance were anamnesis and a scholarly performance test called Teste de Desempenho Escolar, TDE. The results indicated better academic performances from the second group with significant differences in arithmetic, reading and general scores. In a comparison between genders, the girls had better performances than the boys. These results were consistent with the parents’ perception in anamnesis. Although other variables were present, the data showed great academic damage for children with higher lead-poison. These outcomes require political policies to control contamination and intervention in this population.(AU)

La contaminación de niños por plomo ha sido objeto de investigación en el ámbito de la salud pública. En este estudio se evaluó el desempeño académico de 102 niños de la Enseñanza Fundamental. Los participantes fueron divididos en dos grupos: uno con 34 niños no contaminados o con nivel inferior a 5 μg/dl y el otro, de 68 niños, estaba con nivel de contaminación por plomo en la sangre entre 10 y 40 μg/dl. Para evaluación fueron utilizados el Test de Desempeño Escolar (TDE) y anamnesis. Los resultados indicaron mejor desempeño académico para el segundo grupo, con diferencias significantes en aritmética, lectura y desempeño general. La comparación entre los sexos indicó mejor desempeño para niñas, dato coherente con la percepción de los padres en la anamnesis. Aunque otras variables estén presentes, los datos apuntan perjuicios académicos mayores para niños con índices de plomo más altos. Esas descubiertas requieren políticas públicas para control de la contaminación y reducción de los daños en contaminados.(AU)

Avaliação do desempenho escolar de crianças contaminadas por chumbo / Academic performance evaluation of lead-poisoned children / Evaluación del desempeño escolar de niños contaminadas por plomo

A contaminação de crianças por chumbo tem sido objeto de investigação no âmbito da saúde pública. Neste estudo avaliou-se o desempenho acadêmico de 102 crianças do Ensino Fundamental. Os participantes foram divididos em dois grupos: um com 34 crianças não contaminadas ou com nível inferior a 5 μg/dl e o outro, de 68 crianças, estava com nível de contaminação por chumbo no sangue entre 10 and 40 μg/dl. Para avaliação foram utilizados o Teste de Desempenho Escolar (TDE) e anamnese. Os resultados indicaram melhor desempenho acadêmico para o segundo grupo, com diferenças significantes em aritmética, leitura e desempenho geral. A comparação entre os sexos indicou melhor desempenho para meninas, dado coerente com a percepção dos pais na anamnese. Embora outras variáveis estejam presentes, os dados apontam prejuízos acadêmicos maiores para crianças com índices de chumbo mais altos. Esses achados requerem políticas públicas para controle da contaminação e redução dos danos em contaminados.

The lead contamination in children has been the subject of research in the field of public health. This study evaluated the academic performance of 102 children from first to fourth grade. The subjects were divided into two groups. The first group was composed of 34 children without lead poisoning or with poison at levels lower than 5 μg/dl. The second group was composed of 68 children with blood lead levels between 10 and 40 μg/dl. The instruments used to evaluate the academic performance were anamnesis and a scholarly performance test called Teste de Desempenho Escolar, TDE. The results indicated better academic performances from the second group with significant differences in arithmetic, reading and general scores. In a comparison between genders, the girls had better performances than the boys. These results were consistent with the parents’ perception in anamnesis. Although other variables were present, the data showed great academic damage for children with higher lead-poison. These outcomes require political policies to control contamination and intervention in this population.

La contaminación de niños por plomo ha sido objeto de investigación en el ámbito de la salud pública. En este estudio se evaluó el desempeño académico de 102 niños de la Enseñanza Fundamental. Los participantes fueron divididos en dos grupos: uno con 34 niños no contaminados o con nivel inferior a 5 μg/dl y el otro, de 68 niños, estaba con nivel de contaminación por plomo en la sangre entre 10 y 40 μg/dl. Para evaluación fueron utilizados el Test de Desempeño Escolar (TDE) y anamnesis. Los resultados indicaron mejor desempeño académico para el segundo grupo, con diferencias significantes en aritmética, lectura y desempeño general. La comparación entre los sexos indicó mejor desempeño para niñas, dato coherente con la percepción de los padres en la anamnesis. Aunque otras variables estén presentes, los datos apuntan perjuicios académicos mayores para niños con índices de plomo más altos. Esas descubiertas requieren políticas públicas para control de la contaminación y reducción de los daños en contaminados.

Zebrafish as a model for investigating developmental lead (Pb) neurotoxicity as a risk factor in adult neurodegenerative disease: a mini-review.

Lead (Pb) exposure has long been recognized to cause neurological alterations in both adults and children. While most of the studies in adults are related to higher dose exposure, epidemiological studies indicate cognitive decline and neurobehavioral alterations in children associated with lower dose environmental Pb exposure (a blood Pb level of 10µg/dL and below). Recent animal studies also now report that an early-life Pb exposure results in pathological hallmarks of Alzheimer's disease later in life. While previous studies evaluating higher Pb exposures in adult animal models and higher occupational Pb exposures in humans have suggested a link between higher dose Pb exposure during adulthood and neurodegenerative disease, these newer studies now indicate a link between an early-life Pb exposure and adult neurodegenerative disease. These studies are supporting the "fetal/developmental origin of adult disease" hypothesis and present a new challenge in our understanding of Pb neurotoxicity. There is a need to expand research in this area and additional model systems are needed. The zebrafish presents as a complementary vertebrate model system with numerous strengths including high genetic homology. Several zebrafish genes orthologous to human genes associated with neurodegenerative diseases including Alzheimer's and Parkinson's diseases are identified and this model is starting to be applied in neurodegenerative disease research. Moreover, the zebrafish is being used in developmental Pb neurotoxicity studies to define genetic mechanisms of toxicity and associated neurobehavioral alterations. While these studies are in their infancy, the genetic and functional conservation of genes associated with neurodegenerative diseases and application in developmental Pb neurotoxicity studies supports the potential for this in vivo model to further investigate the link between developmental Pb exposure and adult neurodegenerative disease pathogenesis. In this review, the major factors influencing the pathogenesis of neurodegenerative diseases, Pb neurotoxicity, the developmental origin of adult disease paradigm, and the zebrafish as a model system to investigate the developmental origin of low-dose Pb-induced neurodegenerative diseases is discussed.

Niveles de plomo en sangre en niños venezolanos publicaciones en artículos científicos (1993-2006) / Blood lead levels in venezuelan children reported in scientific articles

El objetivo de esta investigación fue realizar una revisión de los níveles de plomo en sangre en niños venezolanos reportados en los artículos científicos publicados entre los años 1993-2996. El estudio fue del tipo documental y las bases de datos consultadas fueron PubMed/MEDLINE, EBDCO, ProQuest, Scielo, REVENCYT, FUNDACID BC UC, utilizando las palabras clave: niños, níveles de plomo en sangre, revisión, Venezuela. En total fueron recopilados 13 artículos, el 85% de estos fueron del tipo descriptivo. La mayor proporción (39%) de estudios revisados fueron clasificados como ambientales. La media de las medias de los níveles de plomo en sangre reportadas en los estudios fue de 12,61 ± 3,95% µg/dL, IC95%[10,23; 14,99 µg/dL]. En el 84,6% de las investigaciones realizadas se observaron medias de plomo en sangre en niños mayores a su límite permisible (10 µg/dL) Esta investigación podría servir de evidencia sobre los niveles de plomo observados en niños venezolanos, contribuyendo con el análisis y discusión de futuras investigaciones.

The objetive of this research was to conduct a review of blood lead levels in venezuelan children reported in the scientific articles published between the years 1993-2006. A documentary study was carried out, databases consulted were PubMed/MEDLINE, EBSCO, ProQuest, Scielo, REVENCYT; FUNDACID BC UC, using key word: children, levels of blood lead, review, Venezuela. Were collected in total 13 articles, 85% of these were descriptive. The largest proportion (39%) of studies reviewed were classified as environmental. The average of the average levels of blood lead reported in the studies was 12.61 ± 3.95 µg/dL, IC95% [10.23; 14.99 µg/dL]. In the 84.6% of investigations carried out in children whit blood lead were it was observed an average of blood lead higher to the allowable limit (10 µg/dL). This research could provide evidence on the blood lead levels observed in venezuelan children, helping with the analysis and discussion of future research.

High prenatal and postnatal lead exposure associated lead encephalopathy in an infant.

An 11-month-old child presented with persistent seizures requiring ventilator support. The child had global developmental delay, was staying in the premises of battery manufacturing unit, had microcytic and hypochromic anemia with basophilic stripling on peripheral smear, lead line on radiograph of the long bones and BLL of 244 µg/dl. The CT scan of the brain revealed cerebral atrophy. The mother also had high BLL and lead line in the radiograph of the long bones. The child was managed with chelation therapy. Given the continuing lead exposure among occupational and general populations in India, this case study highlights the need for prompt environmental preventive actions as well as nutritional and preventive counseling for occupational populations.

Practical guidelines for evaluating lead exposure in children with mental health conditions: molecular effects and clinical implications.

Children in the United States are exhibiting extremely high levels of attentional and learning disabilities. Although lead has been eliminated from many industrial products, children continue to come into contact with it, such as in toys and cosmetics. Lead exposure occurs most commonly in poor, urban populations, and can exacerbate psychiatric disorders associated with stress. We present 1) an overview of lead exposure; 2) a detailed summary of current research on the molecular synergy of toxicity caused by lead and stress; 3) a review of human studies that appear to correlate with these molecular findings, including understanding nutrition, environmental enrichment, and caregiving as risk modifiers; and 4) a systematic approach for mental health practitioners in managing children presenting with multiple symptoms and risk factors for mental health conditions. In this article, we review some of the clinical and scientific challenges that relate to the assessment and treatment of children presenting for mental health care who may have potential lead exposure.

Encephalopathy from lead poisoning masquerading as a flu-like syndrome in an autistic child.

Acute encephalopathy from childhood lead poisoning is fortunately rare. However, in pediatric patients with developmental disabilities and pica, there is a risk of lead exposure at a dose commensurate with encephalopathy, coupled with a risk of delayed diagnosis because of difficulty in distinguishing between baseline and altered behavior. We report here a 4-year old autistic boy who presented to the pediatrician's office with gastrointestinal symptoms and behavioral changes and was at first thought to have a viral syndrome. He returned 2 days later with a worsening illness; increasing pallor, vomiting, abdominal colic, and changes in consciousness were recognized in the emergency department as lead-induced anemia and encephalopathy, associated with a positive abdominal film for paint chips and a blood lead level equal to 216 microg/dL (10.43 micromol/L) (reference, <10 microg/dL or 0.483 micromol/L). As this case illustrates, prompt recognition is dependent on the skills and suspicions of an astute clinician, especially in the busy emergency department.

Lead and conduct problems: a meta-analysis.

This meta-analysis examined the association between conduct problems and lead exposure. Nineteen studies on 8,561 children and adolescents were included. The average r across all 19 studies was .19 (p < .001), which is considered a medium effect size. Studies that assessed lead exposure using hair element analysis yielded considerably larger effect sizes than those that assessed lead exposure using blood, tooth, or bone lead levels. Excluding the 3 hair analysis studies, the average r was .15 (p < .001). The age of the participants did not significantly moderate the relation between lead exposure and conduct problems. Overall, the relation between lead exposure and conduct problems was strikingly similar in magnitude to the relation between lead exposure and decreased IQ.

Brachial plexopathy and nonaccidental injury: role of the neurologist.

Child neurologists must remain vigilant to the possibility of nonaccidental injury. Just as clinicians have become accustomed to considering potential abuse or neglect in children presenting with a head injury or skeletal trauma, physical abuse must also be considered when children present with lesions at other sites of the neuraxis, as illustrated by this child's brachial plexopathy. Key elements from the history can assist clinicians in differentiating accidental events from nonaccidental injuries secondary to abuse or neglect. We report a toddler who presented with a recurrent brachial plexopathy due to nonaccidental injury. Her parents initially denied the occurrence of any significant trauma. Furthermore, her diagnosis was complicated by the identification of concomitant, but unrelated lead toxicity. In this case, the vague and inconsistent parental history, plexopathy recurrence, and identification of a fracture all heightened suspicion of child abuse.

Does background postnatal methyl mercury exposure in toddlers affect cognition and behavior?

Because the toxicological effects of mercury (Hg) are more serious in the developing central nervous system of children than adults, there are growing concerns about prenatal and early childhood Hg exposure. This study examined postnatal methylmercury (MeHg) exposure and cognition and behavior in 780 children enrolled in the Treatment of Lead (Pb)-exposed Children clinical trial (TLC) with 396 children allocated to the succimer and 384 to the placebo groups. Mercury exposure was determined from analyses of blood drawn 1 week before randomization and 1 week after treatment began when succimer had its maximal effect on blood Pb (PbB). The baseline MeHg concentrations were 0.54 microg/L and 0.52 microg/L and post-treatment concentrations were 0.51 microg/L and 0.48 microg/L for placebo and succimer groups, respectively. Because the baseline characteristics in the two groups were balanced and because succimer had little effect on MeHg concentration and no effect on the cognitive or behavioral test scores, the groups were combined in the analysis of MeHg and neurodevelopment. The children's IQ and neurobehavioral performance were tested at age 2, 5 and 7 years. We saw weak, non-significant but consistently positive associations between blood MeHg and IQ test scores in stratified, spline regression and generalized linear model data analyses. The behavioral problem scores were constant or decreased slightly with increasing MeHg concentration. Additional adjustment for PbB levels in multivariable models did not alter the conclusion for MeHg and IQ scores, but did confirm that concurrent PbB was strongly associated with IQ and behavior in TLC children. The effects of MeHg on neurodevelopmental indices did not substantially differ by PbB strata. We conclude that at the present background postnatal MeHg exposure levels of US children, adverse effects on children's IQ and behavior are not detectable.

[Long term consequences among children exposed to lead poisoning]. / Efectos clínicos a largo plazo en niños intoxicados con plomo en una región del sur de Chile.

BACKGROUND: In 1996 there was a massive lead poisoning in a southern rural community in Chile. The contamination source was a mill whose grinding stone was repaired with lead and contaminated the flour. AIM: To assess the presence of sequelae ten years later, among subjects that were exposed to lead on that occasion. MATERIAL AND METHODS: Cross sectional study of 77 individuals (47 males), aged 10 to 25 years, that were exposed to lead in 1996 and were treated with EDTA. RESULTS: Twenty one percent of subjects had a subnormal intelligence quotient (IQ). The risk of having a low IQ was significantly higher among those exposed before the age of six years. IQ was significantly lower among subjects that, immediately after the exposure, had a lead level over 48 microg/dl, compared with those that had a lead level below 43 microg/dl (86.7+/-7.3 and 93+/-11.6 respectively). No subjects with high blood pressure or evidences of nephrotoxicity were detected. CONCLUSIONS: Subjects aged less than six years at the moment of lead exposure had a lower IQ when assessed ten years later.

Efectos clínicos a largo plazo en niños intoxicados con plomo en una región del sur de Chile / Long term consequences among children exposed to lead poisoning

Background: In 1996 there was a massive lead poisoning in a southern rural community in Chile. The contamination source was a mill whose grinding stone was repaired with lead and contaminated the flour. Aim: To assess the presence of sequelae ten years later, among subjects that were exposed to lead on that occasion. Material and methods: Cross sectional study of 77 individuals (47 males), aged 10 to 25 years, that were exposed to lead in 1996 and were treated with EDTA. Results: Twenty one percent of subjects had a subnormal intellingence quotient (IQ). The risk of having a low IQ was significantly higher among those exposed before the age of six years. IQ was significantly lower among subjects that, immediately after the exposure, had a lead level over 48 fig/dl, compared with those that had a lead level below 43 fig/dl (86.7±7.3 and 93±11.6 respectively). No subjects with high blood pressure or evidences of nephrotoxicity were detected. Conclusions: Subjects aged ¡ess than six years at the moment of lead exposure had a lower IQ when assessed ten years later.

Plumbemia en niños de la ciudad de La Plata, Argentina y su relación con la deficiencia de hierro y los factores de exposición al plomo / Blood lead levels in children from the city of La Plata, Argentina. Relationship with iron deficiency and lead esposure risk factors

La exposición ambiental al plomoconstituye un problema de salud pública en todo el mundo y los niños son más vulnerables a sus efectos tóxicos. Numerosas publicaciones demuestran que la deficiencia de hierro y la intoxicación por plomo pueden asociarse, pero en la Argentina los estudios publicados sobre poblaciónpediátrica son escasos. Nuestro objetivofue establecer la plumbemia en niños y determinar su relación con la deficiencia de hierro y con factores de exposición.Población, material y métodos. Se realizó un estudio transversal en 93 niños (6 meses-5 años) que concurrieron al Hospital de Niños de La Plata para controles de salud. Se aplicó una encuesta socioambientaly se determinaron las concentracionesde plomo, hemoglobina y ferritina en sangre.Resultados. La media geométrica de plomo en sangre fue 4,26 μg/dl (IC 95 por ciento: 3,60-5,03), conuna prevalencia de plumbemias ≥ 10 μg/dl de 10,8 por ciento. Se encontraron concentraciones de plomomás elevadas en los niños en cuyos hogares se desarrollaban actividades contaminantes (6,74 contra 3,78 μg/dl; p= 0,005) y en quienes habitabanen viviendas precarias (5,68 contra 3,71μg/dl; p= 0,020). Las plumbemias ≥ 10 μg/dl se asociaron significativamente con la deficiencia de hierro (OR: 5,7; IC 95 por ciento: 1,34-23,41) y conla actividad domiciliaria contaminante (OR: 4,8 IC 95 por ciento: 1,12-20,16).Conclusión. La prevalencia de plumbemias ≥ 10 μg/dl es preocupante en la población estudiada.Los factores de riesgo asociados a dichas concentraciones fueron la deficiencia de hierro y el desarrollo en el hogar de actividades relacionadascon la manipulación de plomo (AU)

Plumbemia en niños de la ciudad de La Plata, Argentina y su relación con la deficiencia de hierro y los factores de exposición al plomo / Blood lead levels in children from the city of La Plata, Argentina. Relationship with iron deficiency and lead esposure risk factors

La exposición ambiental al plomoconstituye un problema de salud pública en todo el mundo y los niños son más vulnerables a sus efectos tóxicos. Numerosas publicaciones demuestran que la deficiencia de hierro y la intoxicación por plomo pueden asociarse, pero en la Argentina los estudios publicados sobre poblaciónpediátrica son escasos. Nuestro objetivofue establecer la plumbemia en niños y determinar su relación con la deficiencia de hierro y con factores de exposición.Población, material y métodos. Se realizó un estudio transversal en 93 niños (6 meses-5 años) que concurrieron al Hospital de Niños de La Plata para controles de salud. Se aplicó una encuesta socioambientaly se determinaron las concentracionesde plomo, hemoglobina y ferritina en sangre.Resultados. La media geométrica de plomo en sangre fue 4,26 μg/dl (IC 95 por ciento: 3,60-5,03), conuna prevalencia de plumbemias ≥ 10 μg/dl de 10,8 por ciento. Se encontraron concentraciones de plomomás elevadas en los niños en cuyos hogares se desarrollaban actividades contaminantes (6,74 contra 3,78 μg/dl; p= 0,005) y en quienes habitabanen viviendas precarias (5,68 contra 3,71μg/dl; p= 0,020). Las plumbemias ≥ 10 μg/dl se asociaron significativamente con la deficiencia de hierro (OR: 5,7; IC 95 por ciento: 1,34-23,41) y conla actividad domiciliaria contaminante (OR: 4,8 IC 95 por ciento: 1,12-20,16).Conclusión. La prevalencia de plumbemias ≥ 10 μg/dl es preocupante en la población estudiada.Los factores de riesgo asociados a dichas concentraciones fueron la deficiencia de hierro y el desarrollo en el hogar de actividades relacionadascon la manipulación de plomo

Cognitive development and low-level lead exposure in poly-drug exposed children.

The impact of early postnatal lead exposure measured at age 4 on children's IQ and academic achievement at and 11 years of age was examined. The sample consisted of 278 inner-city, primarily African American children who were polydrug exposed prenatally. Regression analyses indicated a linear effect of lead exposure on outcomes and no moderating effects of polydrug exposure. An IQ loss of about 4.1-5.4 Full Scale IQ points was estimated for each 10 microg/dL increase in blood lead level at ages 4, 9, and 11 years as a function of blood lead level at age 4. Decrements in scores on tests of non-verbal reasoning were consistently associated with higher lead levels at age 4, while verbal decrements became apparent only at age 11. Lower reading summary scores at 9 and 11 years were consistently associated with higher lead exposure, while decrements in mathematics were not apparent until 11 years. Subgroup analyses on children with blood lead levels <10 microg/dL showed detrimental lead effects even at the 5 microg/dL level, providing additional evidence of adverse effects occurring at blood lead levels below the current 10 microg/dL public health blood lead action level.