Marks et al. specifically, were associated with having ADHD signs using the composite indicator (total DAPs OR = 3.5; 95% CI, 1.1–10.7), which is based on the three assessment methods (i.e., ADHD signs based on least two of the three following measures: maternal report on the CBCL; child performance on the K-CPT; and psychometri- cian ratings on the Hillside scale) and is thus not independent of the individual components. Using creatinine-adjusted DAP levels led to conclusions similar to those presented above [Supplemental Material, Tables 2 and 3 (doi:10.1289/ehp.1002056)]. Some rela- tionships were stronger, whereas others were attenuated. In addition, birth weight, gesta- tional age, breast-feeding, and lead did not confound associations between DAPs and attention or ADHD, because these factors did not change the main effect estimates by > 10% when added to or removed from models. We also tested whether the associations of prenatal DAP concentrations and measures of attention were different for boys and girls, as shown in Table 5 (categorical outcomes) and Table 6 (continuous outcomes). We found evidence for effect modification by sex on the association of prenatal DAP metabolite concen- trations and maternal report of attention prob- lems and ADHD symptoms on the CBCL; at 3.5 years and 5 years, no associations were seen for girls, but among boys, DAP concentrations were significantly associated with poorer atten- tion and ADHD scores (Table 6). We also observed stronger associations among boys than among girls for several categorical outcomes, including CBCL outcomes in the borderline clinical range, high K-CPT Confidence Index scores, scoring ≥ 7 on the Hillside ADHD scale, and the composite measure, but only the interaction terms for the Hillside ADHD scale and composite ADHD indicator models were statistically significant (p < 0.15) (Table 5). R e l a t i o n b e t w e e n c h i l d D A P s a n d attention. We did not observe statistically Table 5. Adjusteda logistic models for attention-related outcomes at 3.5 and 5 years of age per 10-fold increase in prenatal urinary DAP concentrations, stratified by sex. Boys Girls noutcome/n OR (95% CI) noutcome/n OR (95% CI) p-Value for interaction Model 3.5 Years CBCL ADHD 5 Years CBCL ADHD K-CPT Attention problems Attention problems Markedly atypical Percent omissions Percent commissions Hit reaction time ADHD Confidence Index > 70th percentile Hillside Behavioral Rating Scale Attention ≥ 7 of 12 Composite ADHD indicator ADHD indicator Model 3.5 Years CBCL ADHD NEPSY 5 Years CBCL ADHD K-CPT Attention problems Visual attention Attention problems ADHD Confidence Index 1772 significant associations between children’s concurrent total DAP concentrations and any of the measures of attention, whether we adjusted for creatinine or not (Tables 7 and 8) and with or without (not shown) mater- nal DAPs in the models. However, we did observe that for every 10-fold increase in child urinary DE concentration at 5 years, there was a doubling in the odds in the ADHD composite indicator variable (OR = 2.0; 95% CI, 1.1–3.6). We observed no statistically significant increase in adverse outcomes with child DM concentrations. Discussion We found that higher concentrations of OP metabolites in the urine of pregnant women were associated with increased odds of atten- tion problems and poorer attention scores in their young children. This finding was rela- tively consistent using different approaches to assess attentional difficulties, for example, by maternal report, psychometrician observation, or neuropsychological testing. These associa- tions appeared to be somewhat stronger at 5 years than at 3.5 years and were generally stronger in boys than in girls. Children’s con- current total DAP and DM metabolite levels at 3.5 years and 5 years were unrelated to attention outcomes, but we observed some evidence that child DE concentrations at 5 years were adversely related to our compos- ite measure of attention. Although OP pesticides are designed to tar- get the nervous systems of pests, few studies have investigated a possible role for exposure to these chemicals on children’s neurobehavior. Our findings suggest that exposure to OP pesti- cides may affect the attention of young children. Although we did not observe similar associa- tions in this cohort between prenatal DAP con- centrations and attention on the CBCL among 2-year-olds (Eskenazi et al. 2007), such behav- iors may not yet have been evident or consid- ered atypical at this younger age. Our current findings are consistent with those from a cohort study of African- American and Dominican-American children in New York City, which found prenatal blood concentrations of chlorpyrifos to be associated with maternal report of ADHD/ attention problems at 3 years of age (Rauh et al. 2006) using the CBCL, the same instru- ment we used at 2, 3.5, and 5 years of age. Our study is also consistent with a study of a nationally representative sample that reported associations between child DAP concentra- tions (primarily DMs) and ADHD assessed via a parental interview (Bouchard et al. 2010). Children in that study were consider- ably older (8–15 years of age) than our popu- lation. Another study of Hispanic children (mean age = 7 years) living in an agricultural community reported adverse associations of ovlume 118 | number 12 | December 2010 • Environmental Health Perspectives 12/151 12/151 10/154 14/154 21/148 24/148 7/147 14/140 14/153 19/150 4.1 (0.8–22.2) 6.4 (1.1–39.0)** 1.0 (0.2–6.0) 4.9 (0.7–33.0) 1.7 (0.4–6.4) 0.9 (0.2–3.2) 1.2 (0.1–11.5) 10.1 (1.6– 65.3)** 7.9 (1.4–46.0)** 11.1 (1.8– 66.5)# 5/179 6/176 3/168 9/168 38/164 30/164 13/164 11/157 9/169 8/169 n 151 151 143 154 154 140 Boys β (95% CI) 0.7 (0.0 to 1.4)** 1.3 (0.1 to 2.5)** 0.2 (–0.8 to 1.1) 0.9 (0.2 to 1.7)** 1.9 (0.6 to 3.2)# 6.3 (–0.5 to 13.3)* n 179 178 176 168 168 157 2.1 (0.2–29.9) 1.0 (0.1–11.2) 0.6 (0.0–17.3) 0.3 (0.0–2.2) 1.4 (0.5–4.0) 1.2 (0.4–3.3) 1.7 (0.4–7.4) 3.3 (0.6–17.0) 1.0 (0.2–5.9) 1.1 (0.2–7.1) Girls β (95% CI) –0.1 (–0.7 to 0.5) –0.2 (–1.2 to 0.8) 0.2 (–0.7 to 1.2) 0.4 (–0.2 to 1.0) 0.6 (–0.5 to 1.6) 0.5 (–7.2 to 8.3) 0.68 0.21 0.77 0.18 0.90 0.89 0.72 0.41 0.14 0.13 0.05 0.06 0.99 0.28 0.13 0.39 p-Value for interaction aAdjusted for psychometrician, age at assessment, sex, maternal education, depressive symptoms, PPVT, child care, and breast-feeding. **p < 0.05. #p < 0.01. Table 6. Adjusteda linear models for continuous attention-related outcomes at 3.5 and 5 years of age per 10-fold increase in prenatal urinary DAP concentrations, stratified by sex. aAdjusted for psychometrician, age at assessment, sex, maternal education, depressive symptoms, PPVT, child care, and breast-feeding.*p < 0.10. **p < 0.05. #p < 0.01.