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Brenda Eskenazi,¹ Amy R. Marks,¹ Asa Bradman,¹ Kim Harley,¹ Dana B. Barr,² Caroline Johnson,¹ Norma Morga,³ and Nicholas P. Jewell¹

¹Center for Children's Environmental Health Research, School of Public Health, University of California, Berkeley, California, USA; ²National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA; ³Center for the Health Assessment of Mothers and Children of Salinas, Clinica de Salud del Valle de Salinas, Berkeley, California, USA

Abstract
Background: Organophosphate (OP) pesticides are widely used in agriculture and homes. Animal studies suggest that even moderate doses are neurodevelopmental toxicants, but there are few studies in humans.

Objectives: We investigated the relationship of prenatal and child OP urinary metabolite levels with children's neurodevelopment.

Methods: Participating children were from a longitudinal birth cohort of primarily Latino farmworker families in California. We measured six nonspecific dialkylphosphate (DAP) metabolites in maternal and child urine as well as metabolites specific to malathion (MDA) and chlorpyrifos (TCPy) in maternal urine. We examined their association with children's performance at 6 (n = 396) , 12 (n = 395) , and 24 (n = 372) months of age on the Bayley Scales of Infant Development [Mental Development (MDI) and Psychomotor Development (PDI) Indices] and mother's report on the Child Behavior Checklist (CBCL) (n = 356) .

Results: Generally, pregnancy DAP levels were negatively associated with MDI, but child measures were positively associated. At 24 months of age, these associations reached statistical significance [per 10-fold increase in prenatal DAPs: β = –3.5 points ; 95% confidence interval (CI) , –6.6 to –0.5 ; child DAPs: β = 2.4 points ; 95% CI, 0.5 to 4.2]. Neither prenatal nor child DAPs were associated with PDI or CBCL attention problems, but both prenatal and postnatal DAPs were associated with risk of pervasive developmental disorder [per 10-fold increase in prenatal DAPs: odds ratio (OR) = 2.3, p = 0.05 ; child DAPs OR = 1.7, p = 0.04]. MDA and TCPy were not associated with any outcome.

Conclusions: We report adverse associations of prenatal DAPs with mental development and pervasive developmental problems at 24 months of age. Results should be interpreted with caution given the observed positive relationship with postnatal DAPs.

Key words: Bayley Scales of Infant Development, Child Behavior Checklist, DAPs, farmworker, Mexican Americans, neurodevelopment, organophosphates, pervasive developmental disorder, pesticides. Environ Health Perspect 115: 792–798 (2007) . doi:10.1289/ehp.9828 available via http://dx.doi.org/ [Online 4 January 2007]

Address correspondence to B. Eskenazi, Center for Children's Environmental Health Research, School of Public Health, UC Berkeley, 2150 Shattuck Ave., Suite 600, Berkeley, CA 94720-7380 USA. Telephone: (510) 642-3496. Fax: (510) 642-9083 E-mail: eskenazi@berkeley.edu.

We acknowledge the CHAMACOS staff, students, community partners, and participants and families, without whom this study would not be possible. We specifically thank G. Weerasekera, M. Odetokun, M. Gallegos, K. Smith, C. Fernandez, and D. Whitehead for their work on organophosphate pesticide measurements, and N. Holland for her assistance in specimen management.

This publication was made possible by research supported by grant numbers: RD 83171001 from the U.S. Environmental Protection Agency (EPA) , PO1 ES009605 from the National Institute of Environmental Health Sciences (NIEHS) , and RO1 OH007400 from the National Institute for Occupational Safety and Health (NIOSH) . Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIOSH, NIH, or EPA.

The authors declare they have no competing financial interests.

Received 12 October 2006 ; accepted 4 January 2007.