was dichotomized as having a completed col- lege degree (associates, bachelor’s, or gradu- ate) or not. Parents/guardians declared their child’s race after reviewing five different choices: American Indian/Alaskan Native, Asian, Native Hawaiian or Pacific Islander, Black/African American, or White. Due to low sample numbers in nonwhite categories, race was then categorized as white or nonwhite. Parents/guardians initially categorized their children as either Hispanic or non-Hispanic in the questionnaire. Preliminary analysis showed no significant differences by ethnic- ity (data not shown), so this distinction was dropped. When a father’s education was listed as unknown (n = 9), it was imputed as no col- lege degree. Handwipe and dust ∑BDE3 and BDE-153 levels were categorized as tertiles. This allows for the analysis of trends without imposing linearity and reduces the influence of outlier points. Categories for handwipes for ∑BDE3 were low/reference (< 19.0 ng/wipe), medium (19.0 < x < 60.75 ng/wipe), high (> 60.75 ng/wipe). Categories for dust w e r e l o w / r e f e r e n c e ( < 1 0 2 7 . 5 n g / g ) , medium (1027.5 < x < 3,040 ng/g), high (> 3,040 ng/g). Categories for handwipes for BDE-153 were low/reference (< 0.6 ng/wipe), Table 1. Sample population characteristics (n = 83). Characteristic Child’s sex Female Male Child’s age (months) 11–18 19–24 25–36 Child’s race/ethnicity Hispanic Non-Hispanic black Non-Hispanic white Other Marital status of parents Married Unmarried Mother’s education level Some high school Completed high school Some college Completed college Graduate degree Father’s education level Some high school Completed high school Some college Completed college Graduate degree Not reported Breast-feeding < 1 month 1–6 months > 6 months Hours/week away from home 0–12 12–36 > 36 n (%) 42 (51) 41 (49) 26 (31) 34 (41) 23 (28) 16 (19) 21 (25) 43 (52) 3 (4) 55 (66) 28 (34) 8 (10) 8 (10) 12 (14) 25 (30) 30 (36) 10 (12) 11 (13) 7 (8) 18 (22) 28 (34) 9 (11) 20 (27) 21 (28) 34 (45) 33 (40) 24 (29) 26 (31) medium (0.6 < x < 1.6 ng/wipe), high ( > 1 . 6 n g / w i p e ) . C a t e g o r i e s f o r d u s t were low/reference (< 40 ng/g), medium (40 < x < 130 ng/g), high (> 130 ng/g). Exponentiated regression coefficients from models of log-transformed serum PBDE concentrations represent the percent change in the geometric mean (GM) concentration associated with exposure. Statistical signifi- cance was set at α < 0.05. Results Population characteristics. Table 1 presents the characteristics of the toddlers enrolled in this study. Participants were reasonably distributed across sex, age, race, duration of breast-feeding, and parents’ education. After enrollment and blood collection, one individual dropped out from the study and was unavailable for the home visit; hence, handwipe and dust sam- ples were unavailable for this subject. Seven of the 83 fully enrolled individuals did not have blood collected because of collection compli- cations. This resulted in a total of 77 serum samples, 83 handwipe samples, and 81 dust samples collected during this study. PBDEs in serum. PBDEs were detected in all 77 serum samples. The most frequently detected congeners (i.e., detected in > 50% of the samples) were BDEs 47, 99, 100, and 153. BDEs 17, 28, 66, 85, 154, 183, and 209 were also detected in some samples but with lower frequencies (Table 2). BDE-47 was the largest contributor to the ∑pentaBDE concentration measured, ranging from 18% to 72% of the total in individual samples, and averaging 52% overall. BDEs 153, 99, and 100 contributed on average 16%, 15%, and 11% of the ∑pentaBDE concentra- tion. Among the 77 serum samples analyzed, ∑pentaBDE ranged from 5.2 to 668 ng/g lipid with a GM of 42.9 ng/g lipid. PBDEs in handwipes. PBDEs were detected in 81 of the 83 handwipe samples analyzed. The most frequently detected PBDE exposure in U.S. toddlers congeners (i.e., detected in > 50% of the sam- ples) were BDEs 47, 66, 85/155, 99, 100, 153, and 154. BDEs 17, 28, 183, and 209 were also detected at lower frequencies (Table 2). BDEs 47 and 99 were the largest contributors to the total PBDE burden in the handwipes, averag- ing 38% and 33%, respectively, in individual samples. BDE-209 was detected in 27% of the handwipe samples; however, recovery of 13C-BDE-209 was very low in some samples (< 50% in 72% of the samples), and this may have caused a reduced detection frequency that may have biased our results. PBDEs in house dust. PBDEs were detected in all house dust samples analyzed. All major PBDE analytes were detected in > 50% of the samples (Table 2). BDEs 209, 99, and 47 were the largest contributors to the total PBDE concentration in the house dust averaging 48%, 19%, and 18%, respectively. BDE-209 had the highest average concentra- tion in the dust samples, ranging from 441 to 76,130 ng/g with a GM of 2,574 ng/g. Correlations between PBDEs in serum, handwipes and dust. Pearson correlation coefficients were calculated for individual log transformed BDE congeners within and between serum, handwipes, and house dust samples [see Supplemental Material, Table S1 (http://dx.doi.org/10.1289/ehp.1104802)]. PBDEs were highly correlated within each matrix, with correlation coefficients of 0.61 (p < 0.0001) or higher. BDEs 47, 99, and 100 were highly correlated (r > 0.9) with each other within serum, whereas BDE-153 displayed lower correlation coefficients (r = 0.5– 0.7) with the other congeners in serum. The highest correlations between matri- ces were between serum and handwipes for ∑BDE3 (r = 0.59; p < 0.0001; Figure 1). In contrast the association between BDE-153 in serum and handwipes was lower, although still significant: r = 0.31 (p = 0.007). Correlations between handwipes and dust were similar for both ∑BDE3 and BDE-153: 0.36 (p = 0.001) Table 2. Levels of PBDE congeners measured in serum, handwipes, and house dust. Serum (ng/g lipid), n = 77 Handwipes (ng), n = 83 House dust (ng/g), n = 81 % Detect GM % Detect GM % Detect GM Range Congener BDE-17 BDE-28 BDE-47 BDE-66 BDE-85/155 BDE-99 BDE-100 BDE-153 BDE-154 BDE-183 BDE-209 ∑BDE3b ∑PentaBDEc 7.8 26 97 3.9 47 99 95 96 38 18 17 99 100 23.3 6.39 4.97 5.34 35.2 42.9 Range < 0.4–5.3 < 0.4–11.7 < 3.0–350 < 0.4–4.5 < 0.4–10.3 < 1.1–225 < 0.5–67.2 < 0.5–83.1 < 0.4–17.1 < 0.4–1.7 < 6.0–63.8 4.5–642 5.2–668 3.5 45 94 52 72 88 82 82 87 1.1 27a 95 98 16.3 0.32 0.55 13.8 3.2 1.0 0.96 33.7 35.0 Range < 0.5–3.3 < 0.5–14.8 < 2.3–923 < 0.2–67.8 < 0.2–27.7 < 3.1–1,001 < 0.9–228 < 0.3–35.3 < 0.3–46.6 < 1.8–2.1 < 4.5–283 3.2–2,152 3.3–2,187 58 90 100 90 96 100 100 100 100 85 100 100 100 2.7 < 1.2–94 11 < 1.5–277 870 55–24,720 14 < 1.1–916 38 < 0.7–1,860 919 8–36,210 176 9–10,230 88 7–3,407 74 5–3,061 8.6 < 1.8–162 2,574 441–76,130 2,057 145–71,150 2,153 152–74,560 Abbreviations: % Detect, percent detectable; NA, not available. aDetection compromised by low recovery of 13C-BDE-209 during extraction. b ∑BDE3 represents the sum total of BDE congeners 47, 99, and 100. c∑PentaBDE represents the sum total of BDE congeners 47, 99, 100, and 153. Environmental Health Perspectives • volume 120 | number 7 | July 2012 1051