Polybrominated Diphenyl Ethers and Other Persistent Organic Pollutants in Serum Pools from the National Health and Nutrition Examination Survey: 2001–2002

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and persistent pesticides have been measured in serum pools from participants 3–5, 6–11, 12–19, 20–39, 40–59, and ≥60 years of age from the 2001–2002 National Health and Nutrition Examination Survey. For 2,2′,4,4′-tetrabromodiphenyl ether (PBDE-47), the unweighted (not adjusted for sampling weights) arithmetic mean concentration (±95% confidence interval) was 3.4 times higher in 3–5-year-olds (216 ± 30 ng/g of lipid) than in 12–19-year-olds (64 ± 11 ng/g of lipid), with no apparent change with increasing age for adults ≥20 years of age. By contrast, unweighted arithmetic mean concentrations of traditional persistent organic pollutants (POPs) such as hexachlorobenzene (HCB) and 2,2′,3,3′,4,4′,5,5′-octachlorobiphenyl (PCB194) were 2- and 20-fold higher, respectively, in persons ≥60 years than in 12–19-year-old adolescents. Findings suggest higher exposures to PBDEs but lower exposures to traditional POPs in 3–5-year-old children than in adults

Temporal Variability of Polybrominated Diphenyl Ether (PBDE) Serum Concentrations over One Year

Polybrominated diphenyl ethers (PBDEs) are flame retardant chemicals used in consumer products. They are common contaminants in human serum and associated with adverse health effects. Our objectives were to characterize PBDE serum concentrations in a New England cohort and assess temporal variability of this exposure biomarker over a one-year period. We collected three repeated measurements at six-month intervals from 52 office workers from the greater Boston (MA, United States) area from 2010 to 2011. The intraclass correlation coefficient for BDEs 28, 47, 99, 100, and 153 ranged from 0.87 to 0.99, indicating that a single serum measurement can reliably estimate exposure over a one-year period. This was true for both lipid adjusted and nonlipid adjusted concentrations. The kappa statistics, quantifying the level of agreement of categorical exposure classification, based on medians, tertiles, or quartiles ranged from 0.67 to 0.90. Some congeners showed nonsignificant increases from sampling round 1 (winter) to round 2 (summer) and significant decreases from round 2 to round 3 (winter). This study highlights the high reliability of a single serum PBDE measurement for use in human epidemiologic studies

Polybrominated Diphenyl Ethers, Polychlorinated Biphenyls, and Persistent Pesticides in Serum from the National Health and Nutrition Examination Survey: 2003–2008

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and persistent pesticides have been measured in pooled samples representative of the general noninstitutionalized population of the United States. The pools were made from individual sera from the National Health and Nutrition Examination Survey (NHANES) during 2005/06 and 2007/08. The pooled concentrations have been contrasted to NHANES 2003/04 individual measurements to evaluate changes in concentration over time and within survey period differences among age groups, race/ethnicity groups (Mexican American, non-Hispanic Black, non-Hispanic White), and sex. The arithmetic mean serum concentrations of several PCB congeners decreased from NHANES 2003/04 through 2007/08. Larger percentage reductions were seen for younger subjects (12–19 years) compared with older subjects (≥60 years). For example, the arithmetic mean concentration of 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) was 36% lower in 12–19 year old adolescents when comparing NHANES 2007/08 with 2003/04; while for subjects over the age of 60 a 14% lower concentration was seen, although, the 95% confidence intervals overlapped. Similarly, the arithmetic mean serum concentrations of tri- to hexaBDEs were lower in NHANES 2007/08 than in 2003/04; however, most confidence intervals of the arithmetic means overlapped. These findings suggest that a reduction in PBDE serum concentrations cannot yet be detected following the discontinuation of pentaBDE in 2004

Flame Retardant Exposure among Collegiate United States Gymnasts

Gymnastics training facilities contain large volumes of polyurethane foam, a material that often contains additive flame retardants such as PentaBDE. While investigations of human exposure to flame retardants have focused on the general population, potentially higher than background exposures may occur in gymnasts and certain occupational groups. Our objectives were to compare PentaBDE body burden among gymnasts to the general United States population and characterize flame retardants levels in gym equipment, air, and dust. We recruited 11 collegiate female gymnasts (ages 18–22) from one gym in the eastern United States. The geometric mean (GM) concentration of BDE-153 in gymnast sera (32.5 ng/g lipid) was 4–6.5 times higher than in the general United States population groups. Median concentrations of PentaBDE, TBB, and TBPH in paired handwipe samples were 2–3 times higher after practice compared to before, indicating the gymnasts contacted these flame retardants during practice. GM concentrations of PentaBDE, TBB, and TBPH were 1–3 orders of magnitude higher in gym air and dust than in residences. Our findings suggest that these collegiate gymnasts experienced higher exposures to PentaBDE flame retardants compared to the general United States population and that gymnasts may also have increased exposure to other additive flame retardants used in polyurethane foam such as TBB and TBPH

Polybrominated Diphenyl Ethers, 2,2′,4,4′,5,5′-Hexachlorobiphenyl (PCB-153), and <i>p</i>,<i>p</i>′‑Dichlorodiphenyldichloroethylene (<i>p</i>,<i>p</i>′‑DDE) Concentrations in Sera Collected in 2009 from Texas Children

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and <i>p</i>,<i>p</i>′-dichlorodiphenyldichloroethylene (<i>p</i>,<i>p</i>′-DDE) have been measured in surplus serum collected in 2009 from a convenience sample of 300 Texas children (boys and girls) in the birth to 13 years of age range. Serum concentrations of traditional persistent organic pollutants such as 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) and <i>p</i>,<i>p</i>′-DDE did not change consistently with age. By contrast, serum concentrations of tetra-, penta-, and hexa-BDEs were lowest in the youngest children (birth to two year old) and increased 3.0 to 7.9 times, depending on the analyte, for children in the >4 to 6 years of age group. From the apex concentration to the 10 to 13 years of age group, concentrations decreased significantly except for 2,2′,4,4′,5,5′-hexabromodiphenyl ether (PBDE-153), which also had a longer apex concentration of >4 to 8 years of age. This concentration trend for PBDE-153 is most likely due to a longer half-life of PBDE-153 than of other PBDE congeners. The observed PBDEs concentration patterns by age may be related, at least in part, to ingestion of residential dust containing PBDEs through hand-to-mouth behavior among toddlers, preschoolers, and kindergarteners. Further studies to characterize young children’s exposure to PBDEs are warranted and, in particular, to determine the lifestyle factors that may contribute to such exposures

Bidirectional and unidirectional PCET in a molecular model of a cobalt-based oxygen-evolving catalyst

The oxidation of water to molecular oxygen is a kinetically demanding reaction that requires efficient coupling of proton and electron transfer. The key proton-coupled electron transfer (PCET) event in water oxidation mediated by a cobalt-phosphate-based heterogeneous catalyst is the one-electron, one-proton conversion of Co(III)-OH to Co(IV)-O. We now isolate the kinetics of this PCET step in a molecular Co(4)O(4) cubane model compound. Detailed electrochemical, stopped-flow, and NMR studies of the CoIII-OH to Co(IV)-O reaction reveal distinct mechanisms for the unidirectional PCET self-exchange reaction and the corresponding bidirectional PCET. A stepwise mechanism, with rate-limiting electron transfer is observed for the bidirectional PCET at an electrode surface and in solution, whereas a concerted proton electron transfer displaying a moderate KIE (4.3 +/- 0.2), is observed for the unidirectional self-exchange reaction