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Temporal Evaluation of Polybrominated Diphenyl Ether (PBDE) Serum Levels in Middle-aged and Older California Women, 2011-2015. Susan Hurley, Debbie Goldberg, David O Nelson, Weihong Guo, Yunzhu Wang, Hyoung-Gee Baek, Junesoo Park, Myrto Petreas, Leslie Bernstein, Hoda Anton-Culver, and Peggy Reynolds Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b00565 • Publication Date (Web): 17 Mar 2017 Downloaded from http://pubs.acs.org on March 21, 2017
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TITLE: Temporal Evaluation of Polybrominated Diphenyl Ether (PBDE) Serum Levels in
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Middle-aged and Older California Women, 2011-2015.
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AUTHORS: Susan Hurley1*, Debbie Goldberg1, David O. Nelson1, Weihong Guo2,3, Yunzhu
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Wang2, Hyoung-Gee Baek2, June-Soo Park2, Myrto Petreas2, Leslie Bernstein4, Hoda Anton-
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Culver5, Peggy Reynolds1, 6
6 7 8 9 10 11 12 13 14 15
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Cancer Prevention Institute of California, Berkeley, CA, USA;
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Environmental Chemistry Laboratory, Department of Toxic Substances Control, Berkeley, CA,
USA; 3
Food and Drug Laboratory Branch, California Department of Public Health, Richmond, CA
USA; 4
Department of Population Sciences, Beckman Research Institute of the City of Hope, Duarte,
CA, USA; 5
Department of Epidemiology, School of Medicine, University of California Irvine, Irvine, CA, USA; 6
Stanford University School of Medicine, Department of Health Research and Policy, Stanford,
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CA, USA;
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Corresponding Author:
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Susan Hurley,
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Cancer Prevention Institute of California
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2001 Center Street, Suite 700
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Berkeley, CA 94704
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[email protected]
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Office phone: (510) 608-5189
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MANUSCRIPT WORD COUNT: 4391 text + 4 small tables & 1 small figure at 300 each =
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5,891 TOTAL
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ABSTRACT:
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Fax: (510) 666-0693
In response to health concerns and widespread human exposures, two widely-used
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commercial formulations of polybrominated diphenyl ethers (PBDEs) were banned in the United
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States in 2005. Initial biomonitoring data have provided early indications of reduced human
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exposures since these bans took effect. Our objective was to evaluate temporal trends in PBDE
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serum levels among a population of older California women during a four-year period, beginning
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approximately five years after these formulations were banned. Automated solid phase
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extraction and gas chromatography/high resolution mass spectrometry were used to measure
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PBDE levels in blood collected during 2011-2015 among 1,253 women (ages 40-94)
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participating in the California Teachers Study. Only congeners with detection frequencies (DF) >
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75% were included in the present analysis: BDE-47 (DF=88%); BDE-100 (DF=78%); and BDE-
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153 (DF=80%). Results from age- and race/ethnicity-adjusted linear regression analyses
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indicated modest, but statistically significant, average annual percent increases in the serum
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concentrations of all three PBDEs over the four-year study period. While not without limitations,
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these results, in the context of other biomonitoring data, suggest that earlier reported declines in
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PBDE levels may have plateaued and may now be starting to increase. Further biomonitoring to
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ascertain current trends and determinants of population exposures is warranted.
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TOC/ABSTRACT ART:
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KEYWORDS: PBDEs, human exposure, temporal trends, serum
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INTRODUCTION:
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Polybrominated diphenyl ethers (PBDEs) are a class of over 200 congeners introduced in the
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late 1970s as flame retardant additives to a wide variety of consumer products and building
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materials.1 Their use skyrocketed over the ensuing three decades and reports began to emerge
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during the 1990s of rapidly rising body burden levels of PBDEs in human tissues, worldwide and
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within the United States.2-9 These observations, coupled with laboratory evidence of potentially
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associated adverse health effects, including neurodevelopmental toxicity, immunotoxicity,
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endocrine disruption, and carcinogenicity, resulted in the restriction and ban in the production
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and use of PBDEs, both internationally and in the United States.7, 10-12
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PBDEs historically have been used in three primary commercial formulations, containing
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mixtures of compounds; these are named by the average number of bromine atoms of the
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chemical compounds they contain. The Penta- formulation (primarily composed of BDE-99,
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BDE-47, BDE-100, BDE-153,and BDE-154)13 was predominately used to treat polyurethane
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foam cushioning in furniture and carpet padding. The Octa- formulation (primarily composed of
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BDE-183, BDE-207, BDE-203, BDE-209, and BDE-197)13 was used to treat hard plastic casings 3 ACS Paragon Plus Environment
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in computers and other electronic appliances and equipment. The Deca- formulation, almost
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entirely composed of BDE-209,13 was also used in hard plastic casings, as well as in textiles,
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adhesives, and wire insulation.6, 10, 12 In the United States, regulatory and voluntary measures
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resulted in the discontinuation of the production, use, and sale of the Penta- and Octa-
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formulations by the end of 2004 and the Deca-formulation by the end of 2013.10
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In Europe, where PBDEs were phased-out a few years earlier than in the United States, there
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is evidence, although somewhat mixed, that PBDE levels in environmental matrices, wildlife and
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human tissue have been declining.14 In the United States comparatively few data are available to
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evaluate the success of the PBDE phase-outs. Two small biomonitoring studies in California
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have indicated secular decreases in PBDE levels in breast milk15 and blood.16 A larger study of
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newborn blood spots in New York has also suggested secular decreases in body burden levels
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since the 2005 phase-out of the Penta- and Octa- formulations.17 In contrast, although not
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specifically designed to evaluate temporal trends, a pair of small breast milk biomonitoring
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studies in Texas indicated no declines in PBDE levels from 2003 through 2007.18
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The objective of the current analysis was to add to the limited data available to help inform
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the degree to which the phase-out of PBDEs in this country has reduced human exposures.
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Capitalizing on the availability of serum specimens collected from over 1,000 middle-aged and
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older California women participating in an on-going cohort study, we conducted a temporal
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analysis of PBDE serum levels in blood specimens collected from 2011 through 2015.
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MATERIALS AND METHODS:
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Study Population
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The study population consisted of 1,253 participants drawn from the California Teachers
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Study (CTS), a prospective cohort study that recruited 133,479 female professional public school
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employees in 1995-1996 primarily to study breast cancer. A full description of the cohort is
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available elsewhere.19 Women included in the current analysis were serving as controls in an on-
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going breast cancer case-control study nested within the CTS or were recruited separately in a
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convenience sample of breast cancer-free CTS participants which targeted non-whites to enhance
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racial/ethnic diversity. Controls in the case-control study were drawn from a probability sample
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of at-risk cohort members frequency matched to breast cancer cases by age, race/ethnicity and
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broad geographic region (corresponding to the three CTS field collection study sites). The
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convenience sample of breast-cancer free participants was drawn from a probability sample of
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CTS members under the age of 80 years who self-reported as either White, Black, Hispanic or
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Asian/Pacific Islander and were geographically distributed so as to provide approximately equal
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representation of urban and rural residence. Furthermore all participants included in the current
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analysis lived in California and completed a supplementary interviewer-administered
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questionnaire when their blood was drawn between 2011 and 2015. Participants’ ages were
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ascertained by the questionnaire and dates of blood collection were recorded by the interviewer
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at the time blood was collected. Study participants reported their race/ethnicity at recruitment
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into the study on the baseline CTS questionnaire. The use of human subjects was reviewed and
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approved by the California Health and Human Services Agency, Committee for the Protection of
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Human Subjects and all participating centers’ Institutional Review Boards.
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Serum Collection
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Blood was collected from participants between May 9, 2011 and August 24, 2015 by licensed phlebotomists, usually in the participants’ homes. Blood was collected into a 10 mL 5 ACS Paragon Plus Environment
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BD® tube (catalog#367985, Becton Dickinson, Franklin Lakes, NJ) with clot activator, double
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gel for transport, and silicone coated interior using standard phlebotomy techniques. Prior to
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field processing, specimens were kept on cool packs for at least 30 minutes. Within several hours
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of collection, phlebotomists spun down the clotted blood samples in the field using portable
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centrifuges to separate the serum portion. Processed samples were then frozen and stored at -20
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°C for 4-6 weeks until transported either via local courier (on cool-packs) or overnight (on dry-
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ice via FedEx) to the laboratory for chemical analysis. Samples remained frozen during this
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transportation process. Upon receipt at the laboratory, specimens were stored at -20 °C until
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analysis.
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PBDE Analysis
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Serum samples were analyzed for 19 PBDE congeners by the Environmental Chemistry
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Laboratory at the California Department of Toxic Substances Control (Berkeley, CA). Samples
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were thawed and aliquoted for PBDE and lipid measurements. Automated solid phase extraction
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(SPE; Biotage, Uppsala, Sweden) and gas chromatography/high resolution mass spectrometry
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(GC-HRMS, DFS, ThermoFisher, Bremen, Germany) were used for the analysis of PBDEs.20
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Briefly, thawed serum samples (2 mL) were fortified with a panel of 13C12 labeled surrogate
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standards and mixed well. Equal volumes (4 mL) of formic acid and water were added into each
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sample before loading on the SPE modules. Oasis HLB cartridges (3 cc, 500 mg, Waters Co.,
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Milford, MA, USA) and acidified silica (500 oC pre-baked, manually packed, 3 cc) were used for
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the sample extraction and clean-up, respectively. The collected final eluates in hexane:
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dichlomethane (1:1) were concentrated in TurboVap (Biotage, Charlotte, NC, USA), and spiked
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with recovery standards. Standard reference material (SRM 1958, National Institute of Standards
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and Technology, Gaithersburg, MD, USA) and bovine serum pre-spiked with known amounts of 6 ACS Paragon Plus Environment
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target analytes were used as QA/QC samples. The laboratory is proficient in the analysis of
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PBDEs as demonstrated by its regular participation in the performance evaluation system
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managed by the Arctic Monitoring & Assessment Program (AMAP).
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A small volume of sera from each sample was sent to Boston Children’s Hospital for
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measurement of total cholesterol and triglycerides by enzymatic methods.21, 22 Cholesterol and
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triglycerides were used to calculate the lipid content based on Phillips’ formula.23 PBDE levels
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were then normalized for lipids to produce values with units of ng/g lipid. To be consistent with
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national biomonitoring data,24 we replaced concentrations below the laboratory limit of
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detections (LODs) with LOD/√2 before lipid adjustment.
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In order to minimize potential biases associated with imputing high frequency of non-
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detectable levels, only the three congeners with detection frequencies (DF) of 75% or more were
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included in the current analysis. These included: 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47),
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with an average LOD of 0.032 ng/mL and DF=88%; 2,2',4,4',6-Pentabromodiphenyl ether (BDE-
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100), with an average LOD of 0.007 ng/mL and DF=78%; and 2,2',4,4',5,5'-hexabromodiphenyl
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ether (BDE-153), with an average LOD of 0.015 ng/mL and DF=80%.
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Data analyses
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Summary statistics (including means, medians, minimum and maximum values) were
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generated for the lipid-normalized concentration of each congener. Initial evaluations of
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temporal trends were evaluated by plotting the concentration of each PBDE congener versus the
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date of sample collection. Linear models were used to regress the log10-transformed serum
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concentration of each PBDE congener on serum collection date. (Serum concentrations were
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log10-transformed to symmetrize the skewed distributions before using them in regressions). To
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determine appropriate covariates, we conducted backward stepwise regressions, considering age 7 ACS Paragon Plus Environment
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at blood draw (continuous years – considered both as a linear and a quadratic term), and
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race/ethnicity (categorical: White, Black, Hispanic, Asian/Pacific Islander, Other/unknown).
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Regression models were built separately for each PBDE congener and only the factors that were
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significant at p
