Table of Contents

Component Description

Polybrominated diphenyl ethers (PBDEs) and 2,2’,4,4’,5,5’-hexabromobiphenyl (PBB-153) are included in a larger group of chemicals known as brominated flame retardants (BFRs) that are added to products such as foam padding, textiles, or plastics to retard combustion. BFRs are not chemically bound to the flame-retarded material, so they can enter the environment from volatilization, leaching, or degradation of BFR-containing products. PBDEs are generally persistent in the environment and have been measured in aquatic sediments, house dust, and aquatic and terrestrial animals. PBDEs have been shown to bioaccumulate in fish. Humans may be exposed though the diet, including breast feeding, and by contact with BFR-treated products and contaminated house dust. The elimination rate of these BFRs from the human body depends on the specific PBDE congener and can vary from a few weeks to several months. PBB-153 has an elimination half-life measured in decades.

Eligible Sample

Study participants aged 3 years and older from NHANES 2001 - 2002 with stored serum available to prepare pooled samples.

Description of Laboratory Methodology

Serum samples from NHANES 2001-2002 were stored frozen before analysis. Nine polybrominated diphenyl ethers (PBDEs) and PBB-153 were measured in serum through the use of automated solid phase extraction and subsequent sample clean-up. Final determination of target analytes was performed by isotope dilution gas chromatography high-resolution mass spectrometry GC/IDHRMS. The analytical method is described by Sjodin et al., 2004.

Data Processing and Editing

Specimens were processed, stored, and shipped to DLS, NCEH, CDC (Atlanta, Georgia). The analytical approach used, including data processing is described in detail in Sjodin, et al (2004). Reported results met the Division of Laboratory Sciences’ quality control and quality assurance performance criteria for accuracy and precision (similar to specifications outlined by Westgard, 1981).

Laboratory Quality Assurance and Monitoring

The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the General Documentation on Laboratory Data file for detailed QA/QC protocols. The analytical methods are described in the Description of the Laboratory Methodology section.

Analytic Notes

The sampling scheme for NHANES 2001–2002, a complex multistage area probability design, included 11,039 persons. Data were collected through household interviews and through standardized physical examinations conducted in mobile examination centers. On the basis of self-reported data, a composite race/ethnicity variable helped define three major racial/ethnic groups: non-Hispanic blacks, non-Hispanic whites, and Mexican Americans. Informed consent was obtained from all study participants. Serum samples used to prepare pools for analysis were selected from those obtained by venipuncture from 2150 participants, a random one-third subsample of people 12 years of age and older from NHANES 2001-2002 and representative of the U.S. general population for this age range. A total of 1,832 individual serum samples were used to prepare the 54 pooled serum samples analyzed for this subset of NHANES 2001-2002.

After collection of samples, serum specimens were divided into aliquots and were stored cold (2–4°C) or frozen until they were shipped on dry ice to CDC’s National Center for Environmental Health (NCEH). Serum samples were stored frozen after receipt at NCEH at –70°C until analyzed. The 2,150 individual serum samples available were categorized in 24 demographic groups (Table 1), each representing a combination of race/ethnicity, gender, and age (12–19 years, 20–39 years, 40–59 years, and 60 years and older). The number of samples available, the number of these samples that were usable, and the number of pools formed in each demographic group are presented in Table 1. On the basis of the number of individual serum samples per demographic group, multiple pools were available for 14 demographic groups, and one pool was available for 10 demographic groups (Table 1). To ensure that no individual sample overly influenced the pooled results, all serum samples included in any one pool (25.5 mL each) were of equal volume (i.e., each individual sample contributed 750 μL). Most pools included 34 individual serum samples that were randomly selected. Only 31 individual serum samples were available, however, for the pool representing non-Hispanic black men 60 years of age or older. In addition, one of the two pools representing Mexican American men between 20 and 39 years of age consisted of only 33 individual specimens.

In addition, residual serum from 3–11 year old NHANES 2001–2002 participants, previously analyzed for cotinine, a marker of environmental tobacco smoke, was used to create pools representing 3-5 year old and 6-11 year old participants. The 1049 individual samples available were categorized in 12 demographic groups, each representing a combination of race/ethnicity, sex, and age (3–5 years and 6–11 years). A total of 937 randomly selected individual samples were used to prepare 24 pools (two per demographic group). The number of samples available, the number of these samples that were usable, and the number of pools formed in each demographic group are presented in Table 1. To ensure that no individual sample overly influenced the pooled results, all samples included in any one pool were of equal volume (i.e., 0.5 mL). Eleven of the individual serum samples from non-Hispanic black females 3–5 years of age contributed <0.5 mL. Each pool included 21 (3–5 year old) or 57 (6–11 year old) individual samples randomly selected (Table 1).

Table1. Number of individual serum samples available, number of usable samples, and number of pools formed from NHANES 2001–2002 participants per demographic group.

ss_serum_samples_available

Guidelines for Working with Pooled-Samples from NHANES 2001-2002

Because the samples constituting the pools originated from NHANES 2001-2002, which was designed to be representative of the non-institutionalized US population, the pooled results should provide good coverage of the US population. We cannot be assured, however, that estimates based on the pooled samples are unbiased for at least two reasons: 1) the sampling weight information was lost when the samples were pooled because each pool consists of equal volumes of each sample in the pool; and 2) the measured value for a pooled sample (consisting of individual samples that tend to be log-normally distributed) is comparable to an arithmetic average of log-normal results and thus represents a biased estimate of the central tendency (geometric mean or median) of the samples making up the pool. Also, because samples were pooled across the design cells of the original NHANES sampling design, it is not possible to obtain unbiased estimates of standard errors. These bias and standard error issues are being addressed in later NHANES surveys involving pooled samples.

Pooled-Sample weights

The sampling weight information was lost when the samples were pooled because each pool consists of equal volumes of each sample in the pool.

Variance estimation

The sampling scheme for NHANES 2001–2002 is a complex multistage, probability sampling design that selects participants who are representative of the civilian, non-institutionalized U.S. population. Over-sampling of certain population subgroups is done to increase the reliability and precision of health status indicator estimates for those groups. For BFRs, instead of using the full NHANES sample, a random one-third subsample of NHANES participants was used. Curtin et al. (2012) provide documentation of the construction of sampling weights for this one-third subsample. Also, because of the use of stratified multistage selection, incorporation of the sampling design is needed to calculate sampling variances (NCHS, 1994). These variances cannot be calculated for NHANES 2001-2002 pooled sample estimates, however, because samples were pooled across the design cells of the original NHANES 2001-2002 sampling design.

Links to NHANES Data Files

Although this pooled-sample data file cannot be directly linked to other NHANES 2001-2002 data files, it does contain demographic information (RIAGENDR, RIDRAETN, and RIDAGGRP) for each pooled-sample.

 
Variables in the data file

Each variable in the data file is given in Table 2 with its definition. The definition used for the numeric constant for categorical variables is given in the column: Definition of Categorical Variables.

The NHANES abbreviation used for each analyte measured with the IUPAC name is given in Table 3. The code “XYZ” in the variable names “ADJUSTED_RESULT_XYZ” and “RESULT_COMMENT_XYZ” as defined in Table 2 corresponds to the Value of the “NHANES code” in Table 3.

Table 2. NHANES Code, Common Abbreviation and IUPAC Name for each analyte reported
Variable Description Definition of Categorical Variables
POOLID Pool identification number n/a
RIAGENDR Gender of subjects in pool 1 = Male
2 = Female
RIDRAETN Race / Ethnicity of subjects in pool 1 = Non-Hispanic White (NHW)
2 = Non-Hispanic Black (NHB)
3 = Mexican American (MA)
RIDAGGRP Age group of subjects in pool -1 = 3-5 Year old
0 = 6-11 Year old
1 = 12-19 Year old
2 = 20-39 Year old
3 = 40-59 Year old
4 = >60 Years old
RIANSMP Number of samples pool n/a
ADJUSTED_RESULT_XYZ Reported Concentration (ng/g lipid). "XYZ" in the variable name corresponds to the NHANES abbreviation for each analyte. n/a
RESULT_COMMENT_XYZ Code for measured concentration. "XYZ" in the variable name corresponds to the NHANES abreviation for each analyte 0 = Detectable Result
30 = Non-Reportable Result
37 = Result having a concentration below the limit of detection.
The value for the variable "ADJUSTED_RESULT_XYZ" for this analyte corresponds to the limit of detection divided with the square root of 2.

Table 3. NHANES Code, Common Abbreviation and IUPAC Name for each analyte reported
NHANES CODE Common Abbreviation IUPAC Name
BB1 PBB153 2,2’,4,4’,5,5’-Hexabromobiphenyl
BR2 PBDE28 2,4,4’-Tribromodphenyl ether
BR3 PBDE47 2,2’,4,4’-Tetrabromodiphenyl ether
BR4 PBDE85 2,2’,3,4,4’-Pentabromodiphenyl ether
BR5 PBDE99 2,2’,4,4’,5-Pentabromodiphenyl ether
BR6 PBDE100 2,2’,4,4’,6-Pentabromodiphenyl ether
BR66 PBDE66 2,3’,4,4’-Tetrabromodiphenyl ether
BR7 PBDE153 2,2’,4,4’,5,5’-Hexabromodiphenyl ether
BR8 PBDE154 2,2’,4,4’,5,6’-Hexabromodiphenyl ether
BR9 PBDE183 2,2’,3,4,4’,5’,6-Heptabromodiphenyl ether

References

Codebook and Frequencies

POOLID - Pool ID number

Variable Name:
POOLID
SAS Label:
Pool ID number
English Text:
Pool ID number
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
. Missing 0 0

RIAGENDR - Gender

Variable Name:
RIAGENDR
SAS Label:
Gender
English Text:
Gender
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Male 38 38
2 Female 40 78
. Missing 0 78

RIDRAETN - Ethnicity

Variable Name:
RIDRAETN
SAS Label:
Ethnicity
English Text:
Ethnicity
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Non-Hispanic White 35 35
2 Non-Hispanic Black 20 55
3 Mexican American 23 78
. Missing 0 78

RIDAGGRP - Age Group

Variable Name:
RIDAGGRP
SAS Label:
Age Group
English Text:
Age Group
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 6 Yrs. to 11 Yrs. 12 12
1 12 Yrs. to 19 Yrs. 19 31
2 20 Yrs. to 39 Yrs. 13 44
3 40 Yrs. to 59 Yrs. 10 54
4 60 Yrs. to 150 Yrs. 12 66
-1 3 Yrs. to 5 Yrs. 12 78
. Missing 0 78

RIANSMP - Number of samples included in Pool

Variable Name:
RIANSMP
SAS Label:
Number of samples included in Pool
English Text:
Number of samples included in Pool
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
21 to 57 Range of Values 78 78
. Missing 0 78

SSBB1 - PPBB153

Variable Name:
SSBB1
SAS Label:
PPBB153
English Text:
PPBB153
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.4 to 28.5 Range of Values 76 76
. Missing 2 78

SSBR2 - BDE28

Variable Name:
SSBR2
SAS Label:
BDE28
English Text:
BDE28
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.3 to 18.1 Range of Values 77 77
. Missing 1 78

SSBR3 - PBBDE47

Variable Name:
SSBR3
SAS Label:
PBBDE47
English Text:
PBBDE47
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
24 to 316 Range of Values 78 78
. Missing 0 78

SSBR4 - PBDE86

Variable Name:
SSBR4
SAS Label:
PBDE86
English Text:
PBDE86
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.5 to 6 Range of Values 78 78
. Missing 0 78

SSBR5 - PBDE99

Variable Name:
SSBR5
SAS Label:
PBDE99
English Text:
PBDE99
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
5.1 to 89 Range of Values 78 78
. Missing 0 78

SSBR6 - PBDE100

Variable Name:
SSBR6
SAS Label:
PBDE100
English Text:
PBDE100
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4 to 44.8 Range of Values 78 78
. Missing 0 78

SSBR66 - PBDE66

Variable Name:
SSBR66
SAS Label:
PBDE66
English Text:
PBDE66
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.3 to 7.8 Range of Values 77 77
. Missing 1 78

SSBR7 - PBDE153

Variable Name:
SSBR7
SAS Label:
PBDE153
English Text:
PBDE153
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.8 to 37.6 Range of Values 78 78
. Missing 0 78

SSBR8 - PDE154

Variable Name:
SSBR8
SAS Label:
PDE154
English Text:
PDE154
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.4 to 9.5 Range of Values 78 78
. Missing 0 78

SSBR9 - PDE183

Variable Name:
SSBR9
SAS Label:
PDE183
English Text:
PDE183
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.2 to 3.1 Range of Values 76 76
. Missing 2 78