Longitudinal associations between blood lead concentrations lower than 10 microg/dL and neurobehavioral development in environmentally exposed children in Mexico City.
OBJECTIVE
Increasing evidence suggests that 10 microg/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 microg/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 microg/dL than it was among children with levels > 10 microg/dL.


CONCLUSIONS
These analyses indicate that children's neurodevelopment is inversely related to their blood lead levels even in the range of < 10 microg/dL. Our findings were consistent with a supralinear relationship between blood lead levels and neurobehavioral outcomes.
Téllez-Rojo
Martha M
MM
Centro de Investigación en Salud Poblacional, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México. mmtellez@insp.mx
Bellinger
David C
DC
Arroyo-Quiroz
Carmen
C
Lamadrid-Figueroa
Héctor
H
Mercado-García
Adriana
A
Schnaas-Arrieta
Lourdes
L
Wright
Robert O
RO
Hernández-Avila
Mauricio
M
Hu
Howard
H
D002653:Child Behavior Disorders / Q000139:chemically induced* / Q000453:epidemiology; D002675:Child, Preschool; D015986:Confounding Factors, Epidemiologic; D002658:Developmental Disabilities / Q000139:chemically induced* / Q000453:epidemiology; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007854:Lead / Q000009:adverse effects / Q000097:blood*; D020264:Lead Poisoning, Nervous System, Childhood / Q000097:blood* / Q000453:epidemiology; D008297:Male; D008452:Maximum Allowable Concentration; D008800:Mexico / Q000453:epidemiology; D009483:Neuropsychological Tests; D011446:Prospective Studies; D011596:Psychomotor Disorders / Q000139:chemically induced* / Q000453:epidemiology; D011597:Psychomotor Performance; D012959:Socioeconomic Factors; D014505:Urban Population
D007854:Lead