Tofail et al. have also been used before in Bangladesh (Hamadani et al. 2002; Tofail et al. 2006). At the beginning of the study, we assessed interobserver reliabilities among the five tes- ters with 20 infants. Intraclass correlations for scores of both Support and Cover PSTs and Bayley PDI were > 0.95 and for all behavior ratings were > 0.89. We assessed test–retest reliabilities before the start of the study. Test– retest intraclass correlations over 24 hr for both Support and Cover PST scores on 15 infants were > 0.70 and for Bayley PDI on 10 infants over a 7-day interval was 0.9. To maintain quality of testing, we assessed ongo- ing interobserver reliability weekly on 7% of all tests (PSTs and Bayley PDI were > 0.90 and for all behavior ratings were > 0.85). Procedure. Mothers were requested to bring their child to a subcenter for assessments of their child’s development at 7 months of age. All mothers were reimbursed for their travel costs and time, provided with snacks, and the infants were given a toy after the test session. Psychologists who were unaware of the children’s level of arsenic exposure assessed the children’s development in the presence of their Variable Family characteristics Poor housing Occasional or constant income-expenditure deficit Assets (median) Fathers’ education (% < 5th grade) Mothers’ education (% < 5th grade) Mothers’ age (years) Mothers’ parity (% primipara) Mothers’ BMI (kg/m2) Gestational age (weeks) Gestational week 8 and 30 Gestational week 8 Gestational week 30 Infant’s birth anthropometry Weight (g) Length (cm) Head circumference (cm) Age (months) Height for age (Z-score) Weight for age (Z-score) Weight for height (Z-score) Values are mean ± SD or percent. Infant’s characteristics at 7 month testing Arsenic exposure (µg/L) 0–45.0 45.1–97.7 97.8–218 > 218 Total p-Value Group differenceb Linear trend significance (Support). 290 Table 1. Characteristics of families on enrollment and infants at birth and 7 months (n = 1,799). Median of mean arsenic concentration in mothers’ urine (interquartile range) (µg/L) mothers at one of four local clinics. We trained five psychologists to do the developmental assessments, and four of them rotated through each of the subcenters, spending 3 months in a center and then moving to the next one. Statistical analysis. We analyzed data using SPSS for Windows (version 10; SPSS Inc., Chicago, IL, USA). The distribution of urinary arsenic was skewed, so the data were log transformed. Urinary arsenic concentra- tions at 8 and 30 weeks’ gestation were mod- erately well correlated (r = 0.60, n = 1,799, p < 0.001), and we averaged the two values to give exposure throughout pregnancy. First, we categorized the urinary arsenic concentra- tion into quartiles and conducted one-way analysis of variance (ANOVA) controlling for child’s age to examine the difference in developmental scores and behavior ratings by arsenic quartile. We then looked for potential confounders by correlating the sociodemo- graphic variables with the developmental out- comes and with urinary arsenic concentration. We found no significant relationship between the nutritional supplementation group and urinary arsenic concentration (ANOVAs), No. 1,799 1,799 1,799 1,784 1,799 1,799 1,796 1,789 1,799 1,799 1,799 1,799 1,728 1,728 1,728 1,799 1,542 1,542 1,542 –0.05 ± 2.3 (0.32) Value 21 18.7 42 44.5 32 26.4 ± 6.0 20.2 ± 2.7 39.2 ± 1.6 98 (45–218) 81 (37–207) 84 (42–230) 2,696 ± 393 47.8 ± 2.1 32.5 ± 1.7 7.4 ± 0.3 –1.4 ± 1.05 –1.2 ± 1.1 –0.3 ± 1.1 PDI 103.2 ± 15.5 102.8 ± 16.2 103.3 ± 15.0 103.4 ± 15.4 103.2 ± 15.5 and the supplement group did not modify the effect of arsenic on child development, so we did not further consider supplementa- tion in any analyses. To examine the effect of arsenic exposure on infant development, we conducted multiple linear regression analyses of each developmental outcome, controlling for age and offering all covariates that were related to any of the child development mea- sures in univariate analyses, and then entering mean urinary arsenic. We repeated all the regression analyses with the 8- and 30-week urinary arsenic concentrations. Ethics. All mothers were informed about the study and gave consent to participate. In a parallel study in the same area beginning February 2002, we screened all the tube wells for arsenic content (Rahman et al. 2006); we painted red those with water contain- ing > 50 µg/L arsenic and advised people to collect water from green-painted wells with low arsenic concentrations. Unfortunately, the exposure in the study area remained high for most of the studied women (Vahter et al. 2006), generally because of the difficul- ties involved in mitigation. The ICDDR,B research and ethical review committees approved the study. Results Maternal urinary arsenic in early and late preg- nancy and developmental data were available for 1,799 infants. Birth size data were missing for 69 of these infants, mainly because their moth- ers were away for delivery. Anthropometric data at 7 months of age were missing from 255 chil- dren (17.6%) mainly because they were not at home at the time of the home visit. Sample characteristics. Table 1 shows the enrollment characteristics of the parents and characteristics of infants at birth and 7 months. The median (interquartile range) concentration of urinary arsenic at 8 weeks gestation was 81 (37–207) µg/L and at 30 weeks was 84 (42–230) µg/L. Scores for Support differed by sex, with boys doing better than girls (11.38 ± 7 and 10.62 ± 7 respectively, p = 0.023). All three developmental outcomes were related to age at the time of testing (age and Support, r = 0.07; age and Cover, r = 0.08; age and PDI, r = –0.20; p < 0.01 for all). Among five behavior ratings, only cooperation was related to age of testing (age and cooperation, r = –0.05; p < 0.01). We therefore controlled for age when using these variables and sex when analyzing Support. Relation between arsenic and child devel- opment. Table 2 shows the mean develop- mental scores by arsenic quartile. None of the scores varied significantly by urinary arsenic quartile (analyses of covariance, group effect not significant), but the support test showed a significant linear trend (p < 0.05). Similarly, Table 2. Raw scores (mean ± SD) of infant PST (Cover and Support) and PDI by quartiles of maternal mean urinary arsenic concentrationa during pregnancy. No. 450 450 449 450 1,799 0.3 0.8 Total Cover 12.9 ± 7.0 12.7 ± 7.1 13.4 ± 6.8 12.6 ± 7.2 12.9 ± 7.0 0.1 0.018 Total Support 11.5 ± 7.6 11.4 ± 7.9 10.9 ± 7.3 10.4 ± 7.8 11.0 ± 7.6 0.9 0.6 aMean of concentrations at gestational weeks 9 and 30. bANOVA controlling for age (Cover and PDI) and age and sex ovlume 117 | number 2 | February 2009 • Environmental Health Perspectives