Reduced Intellectual Development in Children with Prenatal Lead Exposure

OBJECTIVE: Low-level postnatal lead exposure is associated with poor intellectual development in children, although effects of prenatal exposure are less well studied. We hypothesized that prenatal lead exposure would have a more powerful and lasting impact on child development than postnatal exposure. DESIGN: We used generalized linear mixed models with random intercept and slope to analyze the pattern of lead effect of the cohort from pregnancy through 10 years of age on child IQ from 6 to 10 years. We statistically evaluated dose–response nonlinearity. PARTICIPANTS: A cohort of 175 children, 150 of whom had complete data for all included covariates, attended the National Institute of Perinatology in Mexico City from 1987 through 2002. EVALUATIONS/MEASUREMENTS: We used the Wechsler Intelligence Scale for Children–Revised, Spanish version, to measure IQ. Blood lead (BPb) was measured by a reference laboratory of the Centers for Disease Control and Prevention (CDC) quality assurance program for BPb. RESULTS: Geometric mean BPb during pregnancy was 8.0 μg/dL (range, 1–33 μg/dL), from 1 through 5 years was 9.8 μg/dL (2.8–36.4 μg/dL), and from 6 through 10 years was 6.2 μg/dL (2.2–18.6 μg/dL). IQ at 6–10 years decreased significantly only with increasing natural-log third-trimester BPb (β = −3.90; 95% confidence interval, −6.45 to −1.36), controlling for other BPb and covariates. The dose–response BPb–IQ function was log-linear, not linear–linear. CONCLUSIONS: Lead exposure around 28 weeks gestation is a critical period for later child intellectual development, with lasting and possibly permanent effects. There was no evidence of a threshold; the strongest lead effects on IQ occurred within the first few micrograms of BPb. RELEVANCE TO CLINICAL PRACTICE: Current CDC action limits for children applied to pregnant women permit most lead-associated child IQ decreases measured over the studied BPb range

Blood Lead Secular Trend in a Cohort of Children in Mexico City (1987–2002)

We determined the secular trend in blood lead levels in a cohort of 321 children born in Mexico City between 1987 and 1992. Blood lead level was measured every 6 months during a 10-year period. We modeled the effect of yearly air lead concentration nested within the calendar year in which the child was born, family use of lead-glazed pottery, socioeconomic status, year in which the child was born, age of the child at the time of blood lead measurement, place of residence, and an indicator variable for subjects with complete or incomplete blood lead values. The yearly mean of air lead of the Valley of Mexico decreased from its highest level of 2.80 μg/m(3) in 1987 to 0.07 μg/m(3) in 2002. The contribution of air lead to blood lead according to year of birth was strongest for subjects born in 1987 and fell to nearly zero for children born in 1992. The geometric mean of the entire cohort rose from 8.4 μg/dL in the first year of life to 10.1 μg/dL in the second and decreased thereafter until it reached 6.4 μg/dL at 10 years of age. Children of families who used lead-glazed ceramics had blood lead levels 18.5% higher than did children of nonusing families. Children who belonged to the lowest socioeconomic levels had blood lead levels 32.2% higher than did those of highest socioeconomic levels. Children who lived in the northeast part of the city had blood lead levels 10.9% higher compared with those who lived in the southwest

Niveles de plomo en sangre en niños de 8 a 10 años y su relación con la alteración en el sistema visomotor y del equilibrio Relationship of blood lead levels with visual-motor and equilibrium disturbances in children aged 8 to 10 years

OBJETIVO: Identificar si existe una asociación negativa entre los niveles de plomo en sangre y la coordinación visomotora y el equilibrio de escolares. MATERIAL Y MÉTODOS: Se realizó un estudio transversal en 255 niños de 8 a 10 años de edad, que asistían a escuelas del Sector 1 del Instituto de Educación Pública del Estado de Oaxaca, durante noviembre y diciembre de 1998. Se les aplicaron las pruebas de evaluación de la percepción visual de Frostig y la subescala de equilibrio Frostig Movement Skills Test Battery y se les tomó una muestra de sangre para la determinación de plomo por medio de espectrometría de absorción atómica. Asimismo, se aplicó un cuestionario sociodemográfico y se evaluó la historia de salud del niño. Se relacionó el nivel de plomo sanguíneo con los resultados de las pruebas de percepción visual y del equilibrio mediante modelos de regresión múltiple. Se usó la técnica de simulaciones de Montecarlo para probar el efecto del plomo dentro del modelo. RESULTADOS: La media geométrica de las concentraciones de plomo en sangre fue de 11.5 µg/dl (DE geométrica= +6.3, -5.2). El nivel de plomo se relacionó significativamente con el cociente de integración visomotora (p>0.042). Este disminuye 1.78 (IC 95% -3.51, -0.06) puntos por cada incremento de 10 µg/dl en los niveles de plomo en sangre del niño. De las pruebas que constituyeron este cociente, sólo se relacionó significativamente el plomo con la de coordinación ojo-mano (p=0.045) y de relaciones espaciales (p=0.039). El ingreso familiar también se relacionó significativamente con el cociente de integración visomotora, a mayor ingreso los resultados en las pruebas del niño fueron más altos. Sólo 3.1% de los niños obtuvieron puntuaciones consideradas clínicamente anormales. No se encontró una relación significativa entre el plomo y el cociente de la respuesta motriz reducida, el cociente de percepción visual general y las pruebas de equilibrio. CONCLUSIONES: La relación negativa entre el plomo y la habilidad visomotora concuerda con los resultados encontrados en niños en otros países. Al parecer las concentraciones de plomo en sangre, que son comunes en los niños de Oaxaca, son suficientes para ocasionar una limitación visomotora de naturaleza sutil. Los resultados de este estudio señalan la necesidad de reforzar la iniciativa de reducir la exposición de los niños a las fuentes de exposición conocidas, en especial barro vidriado y, por lo tanto, reducir los niveles poblacionales de plomo en sangre.OBJECTIVE: To assess the association betwen blood lead concentrations and visual-motor coordination and equilibrium in school age children. MATERIAL AND METHODS: In November-December 1998, a cross-sectional study was conducted among 255 children aged 8-10, who attended public schools in Sector 1 of the Oaxaca State Public Education Institute. Data were collected using the Frostig Evaluation of Visual Perception test and the equilibrium subscale of the Frostig Movement Skills Test Battery. A blood sample was taken to measure lead levels by atomic absorption spectrometry. Socioeconomic data and health histories were collected for use as control variables. Statistical analysis consisted of multiple regression models to test the relationship between blood lead level and the visual-motor and equilibrium tests. We assessed the efect of lead within the model using 1 000 Montecarlo simulations. RESULTS: The geometric mean of blood lead concentrations was 11.5 µg/dl (geometric standard deviation +6.3, -5.2). After adjusting for control variables, the visual-motor integration subscale was significantly related to blood lead concentration (p> 0.042). The visual-motor integration value decreased 1.78 (95% CI -3.51, -0.06) points for each 10 µg/dl increase in blood lead concentration. Among the four sub-tests comprising the visual-motor integration subscale, only eye-hand coordination (p=0.045) and spatial relations (p=0.039) were significantly related to blood lead. The visual-motor integration subscale was also significantly related to family income; greater income was related to greater testing scores. Only 3.1% of the children had clinically abnormal testing scores. No statistically significant association was found between blood lead levels and the Frostig subscale Index of Reduced Motor Response, the General Visual Perception Index, or any other equilibrium tests. CONCLUSIONS: The inverse relationship between blood lead concentration and visual-motor skill is consistent with results from studies in other countries. Blood lead levels common among children of Oaxaca are sufficient to produce subtle visual-motor impairments. These findings point out the need to strengthen the initiative to reduce child exposure to known lead sources, particularly lead-glazed ceramics, and thus lower the blood lead levels of the population