Published online August 1, 2006
PEDIATRICS Vol. 118 No. 2 August 2006, pp. e323-e330 (doi:10.1542/peds.2005-3123)

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ARTICLE

Longitudinal Associations Between Blood Lead Concentrations Lower Than 10 µg/dL and Neurobehavioral Development in Environmentally Exposed Children in Mexico City

Martha M. Téllez-Rojo, ScD^a, David C. Bellinger, PhD^b,c, Carmen Arroyo-Quiroz, BSc^a, Héctor Lamadrid-Figueroa, MD^a, Adriana Mercado-García, MD, MPH^a, Lourdes Schnaas-Arrieta, MSc^d, Robert O. Wright, MD, MPH^e, Mauricio Hernández-Avila, MD, ScD^a and Howard Hu, MD, MPH, ScD^c,e

^a Centro de Investigación en Salud Poblacional, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México
^b Department of Neurology, Children's Hospital
^e Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
^c Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts
^d Departamento de Neurobiología del Desarrollo, Instituto Nacional de Perinatologia, Mexico City, Mexico

OBJECTIVE. Increasing evidence suggests that 10 µg/dL, the current Centers for Disease Control and Prevention screening guideline for children's blood lead level, should not be interpreted as a level at which adverse effects do not occur. Using data from a prospective study conducted in Mexico City, Mexico, we evaluated the dose-effect relationship between blood lead levels and neurodevelopment at 12 and 24 months of age.

METHODS. The study population consisted of 294 children whose blood lead levels at both 12 and 24 months of age were <10 µg/dL; blood lead levels were measured by graphite furnace atomic absorption spectroscopy; Bayley Scales of Infant Development II were administered at these ages. The outcomes of interest were the Mental Development Index and the Psychomotor Development Index.

RESULTS. Adjusting for covariates, children's blood lead levels at 24 months were significantly associated, in an inverse direction, with both Mental Development Index and Psychomotor Development Index scores at 24 months. Blood lead level at 12 months of age was not associated with concurrent Mental Development Index or Psychomotor Development Index scores or with Mental Development Index at 24 months of age but was significantly associated with Psychomotor Development Index score at 24 months. The relationships were not altered by adjustment for cord blood lead level or, in the analyses of 24-month Mental Development Index and Psychomotor Development Index scores, for the 12-month Mental Development Index and Psychomotor Development Index scores. For both Mental Development Index and Psychomotor Development Index at 24 months of age, the coefficients that were associated with concurrent blood lead level were significantly larger among children with blood lead levels <10 µg/dL than it was among children with levels >10 µg/dL.

CONCLUSIONS. These analyses indicate that children's neurodevelopment is inversely related to their blood lead levels even in the range of <10 µg/dL. Our findings were consistent with a supralinear relationship between blood lead levels and neurobehavioral outcomes.

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Key Words: lead • children • neurobehavioral

Abbreviations: BSID II—Bayley Scales of Infant Development II • MDI—Mental Development Index • PDI—Psychomotor Development Index

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Accepted Feb 21, 2006.

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eLetters:

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Apparent contradiction to the authors' study published in 2002

joseph scheller

Pediatrics Online, 9 Aug 2006 [Full text]

Response: Apparent contradiction to the authors' study published in 2002

Martha M Téllez-Rojo, et al.

Pediatrics Online, 18 Sep 2006 [Full text]