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Association between Serum Polybrominated Diphenylether Levels and Residential Proximity to Solid Waste Facilities Ruiling Liu, David O Nelson, Susan Hurley, Myrto X. Petreas, Junesoo Park, Yunzhu Wang, Weihong Guo, Leslie Bernstein, Andrew Hertz, and Peggy Reynolds Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b04715 • Publication Date (Web): 24 Feb 2016 Downloaded from http://pubs.acs.org on February 24, 2016
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Environmental Science & Technology
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Association between Serum Polybrominated Diphenylether Levels and Residential
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Proximity to Solid Waste Facilities
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Ruiling Liu1, David O. Nelson1, Susan Hurley1, Myrto Petreas2, June-Soo Park2, Yunzhu Wang2,
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Weihong Guo2, Leslie Bernstein3, Andrew Hertz1, Peggy Reynolds *1, 4
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Cancer Prevention Institute of California, Berkeley, CA, USA;
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Department of Toxic Substances Control, California Environmental Protection Agency,
Berkeley, CA, USA; 3
Department of Population Sciences, Beckman Research Institute of the City of Hope, Duarte,
CA, USA; 4
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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Peggy Reynolds,
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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] 18
Office phone: (510) 608-5180
Fax: (510) 666-0693
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ABSTRACT
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As consumer products treated with polybrominated diphenyl ethers (PBDEs) reach the end of
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their life cycle, they often are discarded into solid waste facilities, offering a potential reservoir
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for exposure. The likelihood of exposures to PBDEs by residents living near those sites rarely
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has been explored. This study collected blood samples from 923 female participants in the
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California Teachers Study in 2011-2013 and examined the association between participants’
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residential proximity to solid waste facilities with potential release of PBDEs and serum levels of
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three congeners (BDE-47, BDE-100 and BDE-153). General linear regression analysis was used
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to examine the association, adjusting for age, race, body mass index, neighborhood
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socioeconomic status and urban residency. Compared to participants living >10 km from any
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selected site, those living within 2 km had 45% higher BDE-47 (95% CI: 5-100%) and BDE-100
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(95% CI: 0-109%) levels, and those living between 2-10 km had 35% higher BDE-47 (95% CI:
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0-82%) and 29% higher BDE-100 (95% CI: -9 to 82%) levels. No associations were found for
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BDE-153. Living close to some solid waste sites may be related to higher serum BDE-47 and
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BDE-100 levels. Studies with comprehensive exposure assessments are needed to confirm these
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initial observations.
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TOC/ABSTRACT ART
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Environmental Science & Technology
INTRODUCTION
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Polybrominated diphenylethers (PBDEs) have been widely used as flame-retardants in
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various products, including plastics, wire insulation, building materials, household and business
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furnishings, and automobiles
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their life cycle, from PBDE production to the use and final disposal of PBDE-treated consumer
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products. As illustrated in Supplemental Figure S13, PBDEs are transported via multiple media,
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including air, soil and water, and accumulate in the food chain. PBDEs have been detected in
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house dust, in both indoor and outdoor air, and in different food groups in many countries
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worldwide 4. PBDEs are also found in various waste streams, such as electronic waste, auto-
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shredder waste and sewage sludge 5, and in landfill leachate 6. Since PBDEs are persistent and
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ubiquitous in multiple environmental media, human exposure can occur via multiple routes,
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including ingestion of contaminated food, dust and water, inhalation of gas and dust/particles
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from indoor or outdoor air, and dermal absorption of dust or via contacts with various consumer
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products. The relative contribution of each of these routes has not been well-characterized and is
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likely changing as PBDE-laden products are moving from wide-spread use to disposal into the
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solid waste stream.
1, 2
. PBDEs can be emitted into the environment in each phase of
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There is evidence that PBDE levels among Americans are much higher than among Asians
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and Europeans 7, and Californians have higher PBDE levels than the rest of the U.S. population,
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likely due to California’s furniture flammability standard 8. Accumulating evidence shows that
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human body levels of PBDEs are associated with measured PBDE levels in house dust, as well
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as consumption of dairy products, meat or fish 9-11. It has been estimated that dust/soil ingestion
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and dermal contact might explain 90% of an U.S. adult’s daily exposure of total PBDEs 7.
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Laboratory studies have shown that PBDEs may have endocrine disrupting properties and
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12-17 18
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are associated with multiple neurobehavioral, developmental and reproductive effects
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Epidemiological studies, while limited, have also observed some human health risks associated
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with PBDE exposure 19-21 22.
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Due to concerns about PBDEs’ impact on human health and the environment, California
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banned the two most commonly used formulations, penta- and octa-BDEs in 2006 23, and all uses
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of deca-BDE were required to end by the end of 2013 7. As a result, indoor exposures from
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dust/off gassing of PBDEs associated with the use of PBDE-laden consumer products are likely
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to become a less important route of exposure while outdoor exposures may become more
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predominant. Thus, evaluating whether people's body burden of PBDEs may be associated with
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residential exposure to PBDEs from solid waste disposal sites is of public health significance as
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it may provide important implications for solid waste management to reduce future exposures to
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these chemicals.
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Two studies have reported an association between body levels of PBDEs and potential
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residential exposures related to waste disposal sites. One was conducted in China comparing
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workers in an electronic waste dismantling region, to nearby residents and the general population
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. The other was conducted in Nicaragua among young people working at and/or living near a
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large municipal waste disposal site 25. Both of these studies, however, were designed to examine
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occupational exposures to PBDEs and compare them to exposures in nearby residents who may
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have also been occupationally exposed. To our knowledge, no studies to date have been designed
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to examine people’s residential exposure from waste disposal facilities among the general U.S.
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population without substantial occupational exposures.
The objective of our study was to
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evaluate the association between residential proximity to solid waste facilities and serum levels
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of PBDEs among a sample of California adult women.
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Materials and Methods
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Study Population
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The study population consisted of 923 participants drawn from the California Teachers
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Study (CTS), a prospective cohort study consisting of 133,479 female professional public school
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employees initiated in 1995-96 primarily to study breast cancer. A full description of the cohort
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is described elsewhere
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controls in an on-going breast cancer case-control study nested within the CTS and a
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convenience sample of additional breast cancer-free CTS participants which targeted non-whites
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to ensure racial/ethnic diversity. Participants were required to have no prior history of breast
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cancer, live in California, and complete a supplementary interviewer administered questionnaire
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at the time of the blood draw in 2011-2013. 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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. Participants for the current analysis consisted of women serving as
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Blood was collected from participants during 2011-2013 by licensed phlebotomists,
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usually in the participants’ homes. Specimens were kept on cool packs and within several hours
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of collection spun down using portable centrifuges to separate the serum portion. Processed
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samples were then frozen and transported to the laboratory where they remained frozen and
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stored at -20 °C until thawed for the PBDE assays.
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PBDE Analysis 5 ACS Paragon Plus Environment
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Serum PBDEs were analyzed by the Environmental Chemistry Laboratory at the California
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Department of Toxics Substance Control (Berkeley, CA). Samples were thawed and aliquoted
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for PBDE and lipids measurements. Automated solid phase extraction (SPE; Biotage, Uppsala,
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Sweden) and gas chromatography/high resolution mass spectrometry (GC-HRMS, DFS,
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ThermoFisher, Bremen, Germany) were used for the analysis of PBDEs
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serum samples (2 mL) were fortified with a panel of
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(Wellington Laboratories, Inc., Guelph, Ontario, Canada) and mixed well. Equal volumes (4 mL)
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of formic acid and water were added into each sample before loading on the SPE modules. Oasis
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HLB cartridges (3 cc, 500 mg, Waters Co., Milford, MA, USA) and acidified silica (500 oC pre-
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baked, manually packed, 3 cc) were used for the sample extraction and clean-up, respectively.
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The collected final eluates in hexane: dichlomethane (1:1) were concentrated in TurboVap
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(Biotage, Charlotte, NC, USA), and spiked with recovery standard. Standard reference material
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(SRM 1958, National Institute of Standards and Technology, Gaithersburg, MD, USA) and
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bovine serum pre-spiked with known amounts of target analytes were used as QA/QC samples.
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. Briefly, thawed
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C12 labeled surrogate mix standards
A small volume of sera from each sample was sent to Boston Children’s Hospital for 28, 29
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measurement of total cholesterol and triglycerides by enzymatic methods
. Cholesterol and
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triglycerides were used to calculate the lipid content based on Phillips’ formula 30. PBDE levels
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were then lipid adjusted to produce values with units of ng/g lipid.
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While a total of 19 congeners were analyzed in the laboratory, only those with detection
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frequencies of 75% or more were included in the current analysis in order to minimize potential
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biases associated with imputing high frequency of non-detectable levels. Detection frequencies
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ranged from 0.3% for BDE-17 to 87.4% for BDE-47. Although not meeting the detection
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frequency criteria sufficient for inclusion in the current analysis, BDE-99 and BDE-28 were 6 ACS Paragon Plus Environment
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detected in a substantial proportion of study participants, with 42.3% and 43.0% detected,
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respectively. The three congeners for which ≥75% were detected and therefore included in this
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study were: 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), 2,2',4,4',6-Pentabromodiphenyl ether
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(BDE-100) and 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153). To be consistent with
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standard national biomonitoring data, we used a simple but common practice to replace
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concentrations below the laboratory limit of detections (LODs) with LOD/√2 before lipid
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adjustment. For the 923 participants, the means (ranges) of lipid-adjusted LODs for BDE-47,
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BDE-100 and BDE-153 were 4.90 (1.32-17.64), 1.11 (0.23-4.41) and 2.31 (0.50-8.82) ng/g lipid,
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respectively.
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Identification of Solid Waste Disposal Facilities with Potential Emission of PBDEs
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Information on solid waste disposal facilities throughout California was obtained from the
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database available on the website of the Solid Waste Information System (SWIS) of California's
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Department of Resources Recycling and Recovery 31. The database is updated frequently. Data
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used in this study were downloaded on May 28, 2013. While these data do not include any
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specific information about potential PBDE exposures, we selected for inclusion in our study only
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those facilities that were likely to serve as potential sources of PBDE exposure based on the
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limited knowledge contained in the dataset regarding the activities and materials handled at each
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SWIS facility. Because the blood samples in our study were collected between 2011-2013, serum
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PBDE levels were unlikely to be related to exposures that might have occurred 30 years ago, so
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we excluded those closed before Jan 01, 1980. For the same reason, facilities designated "pre-
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regulation" (i.e., sites that ceased operations prior to August 15, 1977, when solid waste facility
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permits began to be required) were also excluded. There is no information on close date for those
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facilities, so they were excluded not based on specific close date but by their "pre-regulation" 7 ACS Paragon Plus Environment
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status. As asbestos can be used as a kind of fire retardant, we think that asbestos containing
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materials are less likely to have PBDEs added, thus asbestos containing waste disposal facilities
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were excluded.
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There was a total of 3,186 facility entries listed in the SWIS database, and facilities that are
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not likely to emit PBDEs were excluded sequentially, based on the rationale presented above, as
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follows: 1) closed before Jan 01, 1980 (n=572); 2) in planning stages when the database was
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updated or “clean closed” with documented removal of solid waste (n=74); 3) “pre-regulations”
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(ceased operations prior to August 1977, n=296); 4) composting sites accepting non-hazardous
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vegetable, yard and wood wastes (n=397); 5) waste tire sites storing, stockpiling, discarding,
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collecting or processing waste tires (n=8); 6) involved in the following activities (n=93): asbestos
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containing waste disposal, land application, construction and demolition wood debris chipping
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and grinding, non-hazardous petroleum contaminated soil disposal, sealed container transfer
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operation, wood waste disposal or sludge drying, or served as septage ponds, drilling mud
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impoundments or leachate evaporation ponds; 7) duplications with the same facility address
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(n=176). A total of 1,570 facilities were included in our study, 864 (55%) of which were solid
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waste landfills (disposal sites) and the remainder were transfer/processing facilities which were
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utilized to receive solid wastes, temporarily store, separate, convert, or otherwise process the
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materials in the solid wastes, or to transfer the solid wastes directly from smaller to larger
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vehicles for transport, and those facilities utilized for transformation.
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Calculating Participants’ Residential Distance to Selected SWIS Facilities
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Latitude/longitude coordinates of SWIS facilities were downloaded from the SWIS
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website. Participants’ residential addresses at time of blood draw were standardized using
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address cleaning software (ZP4, Semaphore Corp.) and geocoded against parcel and then street 8 ACS Paragon Plus Environment
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centerline databases, and their distances to selected facilities were calculated. Addresses. All GIS
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was performed using ArcGIS 9.2 (ESRI, Redlands, CA, USA).
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Participants’ Neighborhood Characteristics
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Neighborhood socioeconomic status (SES) was derived by geocoding participants’
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residential addresses to U.S. Census 2000 block groups. Measures of block group SES were
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based on a previously-developed method that incorporates census-based measures of income,
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occupation, and education at block group level32. This variable was then categorized into
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quintiles, with the first quintile representing the lowest and the fifth quintile the highest summary
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measure of neighborhood SES across the 31,269 block groups in California in 2010. Each
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participant was assigned this composite measure of neighborhood SES based on her geocoded
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block group.
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Participants’ residential addresses also were assigned an urbanization level according to
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the 2010 census urban classification scheme. 33 Participants were classified as living in an urban
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area (region of ≥50,000 people), an urban cluster (region of between 2,500 and 50,000 people) or
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a rural area (region of 2 -10 km, and > 10 km, with >10 km as the reference group.
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Analyses including only non-movers, i.e., those who had the same residential addresses at
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baseline in 1995/96 and at the time of blood draw, were also conducted to reduce potential
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misclassification due to address changes prior to blood draw.
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RESULTS
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Table 1 presents the lipid-adjusted serum PBDE levels for each of the three congeners by
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participant characteristics. Of the 923 participants included in this study, 82% were 50 to 79
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years old at the time of blood draw, 69% were non-Hispanic white, 37% had BMI of 25 kg/m2 or
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greater, 63% lived in neighborhoods with relatively higher SES (the 4th and 5th quintiles), and
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90% lived in urban areas. The detection frequencies for BDE-47, BDE-100 and BDE-153 were
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87%, 77% and 79%, respectively, and the geometric means (GMs) were 14.21, 2.46 and 5.51
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ng/g lipid for these three congeners, respectively. Serum levels (log10 transformed) of these three
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congeners were statistically significantly (p
