Barr et al. 1999–2000 and NHANES 2001–2002. white Americans were oversampled beginning and included examinations of 9,282 people; The study was reviewed and approved by the in 2000. Data were collected through a house- NHANES 2001–2002 was conducted in 30 Ethical Review Board at the NCHS and com- hold interview and a standardized physical locations and included examinations of 10,000 plied with all national and international guide- examination that was conducted in a mobile people. For the pyrethroid metabolites in the lines on research involving human subjects. examination center. Spot urine specimens first NHANES cycle, we conducted measure- The sampling scheme for NHANES is were collected from each participant ≥ 6 years ments on a subset of participants based on based on a complex multistage area probabil- of age during one of three daily examination a random one-half sample of children 6–11 ity design, which includes selection of pri- periods. Sociodemographic information and years of age in 1999 and 2000, a random one- mary sampling units (counties), household medical histories of the survey participant and quarter sample of people 12–59 years of age segments within the counties, and sample the family were collected during the house- in 1999, and a random one-third sample of persons from selected households. In 1999 hold interview. Fasting duration was also col- people 12–59 years of age in 2000. For the and 2000, people 12–19 years and ≥ 60 years lected from each participant. second NHANES cycle, we conducted meas- of age, non-Hispanic blacks, and Mexican NHANES 1999–2000 was conducted urements on a subset of participants based on Americans were oversampled. Low-income in 26 locations throughout the United States a one-half sample of children 6–11 years of age Table 2. Urinary concentrations of 3PBA in the general U.S. population, NHANES 1999–2002. Selected percentile (95% confidence interval) Category/ GM (95% confidence Sample Weighted survey years interval) 50th 75th 90th 95th size (n) detection (%) Total 1999–2000a 0.292 (0.247–0.345) 0.25 (0.19–0.32) 0.73 (0.59–0.85) 1.75 (1.49–2.16) 4.33 (2.62–6.30) 1,998 66.5 2001–2002a 0.318 (0.275–0.368) 0.27 (0.22–0.34) 0.70 (0.57–0.81) 1.73 (1.49–2.16) 3.54 (2.69–5.25) 3,048 75.4 1999–2000b 0.261 (0.224–0.304) 0.25 (0.20–0.28) 0.55 (0.46–0.63) 1.40 (1.13–1.73) 3.19 (2.16–4.55) 1,998 66.5 2001–2002b 0.324 (0.284–0.371) 0.29 (0.25–0.34) 0.60 (0.51–0.75) 1.54 (1.26–1.91) 3.35 (2.50–4.92) 3,046 75.4 Age group 6–11 years 1999–2000a 0.417 (0.292–0.595) 0.32 (0.21–0.49) 10.12 (0.70–1.60) 4.18 (2.02–6.54) 8.63 (3.89–71.1) 483 71.9 2001–2002a 0.325 (0.260–0.406) 0.30 (0.20–0.42) 0.76 (0.57–1.05) 1.81 (1.42–2.78) 3.38 (2.25–4.12) 580 75.2 1999–2000b 0.450 (0.299–0.677) 0.30 (0.19–0.44) 0.89 (0.57–1.35) 2.59 (1.41–5.49) 7.20 (1.88–64.0) 483 71.9 2001–2002b 0.423 (0.335–0.534) 0.33 (0.25–0.41) 0.66 (0.49–1.06) 1.81 (1.28–2.58) 3.04 (2.00–4.09) 580 75.2 12–19 years 1999–2000a 0.336 (0.265–0.427) 0.29 (0.20–0.44) 0.87 (0.62–1.04) 1.93 (1.49–2.90) 4.33 (1.83–11.1) 682 73.2 2001–2002a 0.353 (0.288–0.434) 0.30 (0.25–0.39) 0.80 (0.56–1.13) 1.86 (1.48–2.35) 3.45 (2.14–6.69) 831 79.8 1999–2000b 0.227 (0.178–0.290) 0.16 (0.12–0.20) 0.39 (0.29–0.52) 1.16 (0.71–1.39) 1.65 (1.25–4.21) 682 73.2 2001–2002b 0.274 (0.229–0.328) 0.21 (0.18–0.25) 0.46 (0.35–0.61) 1.01 (0.72–1.46) 1.69 (1.10–5.48) 830 79.8 20–59 years 1999–2000a 0.267 (0.227–0.314) 0.23 (0.16–0.30) 0.64 (0.51–0.82) 1.49 (1.25–1.78) 3.21 (2.04–5.41) 833 64.2 2001–2002a 0.314 (0.271–0.364) 0.27 (0.22–0.34) 0.67 (0.53–0.78) 1.65 (1.27–2.34) 3.25 (2.51–6.16) 1,128 75.8 1999–2000b 0.246 (0.216–0.278) 0.26 (0.22–0.29) 0.55 (0.46–0.63) 1.30 (1.04–1.62) 2.86 (1.97–4.18) 833 64.2 2001–2002b 0.311 (0.271–0.357) 0.30 (0.26–0.35) 0.60 (0.50–0.75) 1.59 (1.15–2.46) 3.43 (2.37–5.11) 1,128 75.8 ≥ 60 years 2001–2002a 0.303 (0.233–0.394) 0.25 (0.18–0.35) 0.69 (0.49–1.10) 2.03 (1.45–3.68) 5.16 (2.77–6.61) 509 70.3 2001–2002a 0.372 (0.301–0.462) 0.32 (0.24–0.41) 0.73 (0.54–1.02) 2.16 (1.28–3.50) 4.06 (2.44–6.15) 508 70.3 Sex Male 1999–2000a 0.273 (0.226–0.330) 0.25 (0.18–0.33) 0.71 (0.57–0.82) 1.49 (1.29–1.73) 2.41 (1.92–3.79) 974 65.3 2001–2002a 0.326 (0.281–0.379) 0.30 (0.23–0.36) 0.69 (0.57–0.75) 1.60 (1.37–2.15) 3.23 (2.56–5.25) 1,429 77.8 1999–2000b 0.210 (0.173–0.253) 0.19 (0.15–0.25) 0.51 (0.39–0.59) 1.13 (0.86–1.49) 1.85 (1.49–2.53) 974 65.3 2001–2002b 0.269 (0.233–0.310) 0.24 (0.20–0.28) 0.50 (0.43–0.58) 1.28 (1.05–1.59) 3.00 (1.74–4.00) 1,429 77.8 Female 1999–2000a 0.311 (0.253–0.384) 0.25 (0.19–0.34) 0.74 (0.51–0.99) 2.30 (1.63–3.36) 6.03 (3.27–11.8) 1,024 67.7 2001–2002a 0.311 (0.260–0.371) 0.25 (0.20–0.32) 0.73 (0.55–0.92) 1.81 (1.53–2.47) 3.76 (2.51–6.55) 1,619 73.1 1999–2000b 0.323 (0.270–0.387) 0.28 (0.24–0.34) 0.60 (0.47–0.71) 1.88 (1.31–2.86) 5.03 (3.08–6.90) 1,024 67.7 2001–2002b 0.388 (0.331–0.455) 0.33 (0.28–0.41) 0.73 (0.56–0.93) 1.84 (1.45–2.35) 4.43 (2.62–5.59) 1,617 73.1 Race/ethnicity Non-Hispanic white 1999–2000a 0.288 (0.233–0.355) 0.24 (0.16–0.32) 0.71 (0.53–0.85) 1.78 (1.41–3.05) 5.34 (2.62–8.43) 603 65.1 2001–2002a 0.297 (0.248–0.355) 0.24 (0.19–0.32) 0.60 (0.49–0.78) 1.75 (1.46–2.34) 3.70 (2.52–6.16) 1,281 73 1999–2000b 0.272 (0.225–0.329) 0.28 (0.23–0.34) 0.63 (0.51–0.80) 1.88 (1.35–2.53) 4.44 (2.29–5.93) 603 65.1 2001–2002b 0.321 (0.274–0.377) 0.31 (0.26–0.36) 0.67 (0.53–0.91) 1.84 (1.46–2.62) 4.43 (2.63–6.04) 1,280 73 Mexican American 1999–2000a 0.260 (0.230–0.295) 0.23 (0.19–0.27) 0.60 (0.43–0.75) 1.35 (1.16–1.53) 2.18 (1.53–3.26) 697 68.1 2001–2002a 0.290 (0.233–0.361) 0.26 (0.19–0.35) 0.65 (0.49–0.81) 1.26 (0.86–2.17) 2.65 (1.50–3.44) 767 76 1999–2000b 0.234 (0.202–0.272) 0.16 (0.13–0.19) 0.31 (0.27–0.39) 0.64 (0.49–0.95) 1.06 (0.67–1.71) 697 68.1 2001–2002b 0.274 (0.230–0.328) 0.20 (0.18–0.24) 0.39 (0.31–0.48) 0.73 (0.58–0.96) 1.18 (0.79–1.98) 767 76 Non-Hispanic black 1999–2000a 0.454 (0.352–0.586) 0.45 (0.35–0.61) 1.13 (0.75–1.46) 2.32 (1.45–5.35) 5.35 (2.32–21.1) 524 80.3 2001–2002a 0.507 (0.430–0.599) 0.52 (0.44–0.63) 0.98 (0.84–10.20) 2.03 (1.72–2.52) 3.86 (3.05–5.84) 776 88.7 1999–2000b 0.309 (0.238–0.401) 0.25 (0.20–0.32) 0.58 (0.39–0.78) 1.36 (0.89–2.79) 3.43 (1.39–5.44) 524 80.3 2001–2002b 0.374 (0.308–0.455) 0.32 (0.25–0.39) 0.59 (0.50–0.69) 1.29 (0.93–1.66) 2.62 (1.58–3.26) 775 88.7 < LOD indicates less than the LOD for the uncorrected urine values, which may vary for some chemicals by year. n-Values may differ because some information was missing for a particular subgroup. aVolume-based concentrations (ng/mL). bCreatinine-adjusted concentrations (μg/g creatinine). 744 118 | number 6 | June 2010 • Environmental Health Perspectives ovlume