Table of Contents

Component Description

Organochlorine pesticides are a diverse group of synthetic chemicals that persist in the environment and tend to bio accumulate. Most of these chemicals have been banned from use in the U.S. Assessment of exposure to persistent organochlorine pesticides in a representative sample of the U.S. population is needed to determine current prevalence and level of exposure and the potential for human health effects from exposure to these chemicals.

Eligible Sample

Examined participants aged 12 years and older from a one-third subsample were eligible.

Description of Laboratory Methodology

Eight organochlorine pesticides and metabolites were measured in serum through the use of automated liquid/liquid 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 in Jones et al, 2012, which is a modification of the method described by Sjodin et al., 2004 and Barr et al., 2003.

Refer to the Laboratory Methods Files section for a detailed description of the laboratory methods used. 

There were no changes to the lab method, lab equipment, or lab site for this component in the NHANES 2005-2006 cycle.  However, the samples were measured in a pooled fashion for 2005-2006 rather than individual measurements.

Laboratory Quality Assurance and Monitoring

Serum samples were processed, stored and shipped to the Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA for analysis. 

Detailed instructions on specimen collection and processing are discussed in the NHANES Laboratory Procedure Manual (LPM). Vials are stored under appropriate frozen (-30oC) conditions until they were shipped to the National Center for Environmental Health for testing. 

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 LPM.

Mobile Examination Centers (MECs)

Laboratory team performance is monitored using several techniques. NCHS and contract consultants use a structured competency assessment evaluation during visits to evaluate both the quality of the laboratory work and the quality-control procedures. Each laboratory staff member is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff member. Formal retraining sessions are conducted annually to ensure that required skill levels were maintained.

Analytical Laboratories

NHANES uses several methods to monitor the quality of the analyses performed by the contract laboratories. In the MEC, these methods include performing blind split samples collected during “dry run” sessions. In addition, contract laboratories randomly perform repeat testing on 2% of all specimens.

NCHS developed and distributed a quality control protocol for all CDC and contract laboratories, which outlined the use of Westgard rules (Westgard, et al. 1981) when running NHANES specimens. Progress reports containing any problems encountered during shipping or receipt of specimens, summary statistics for each control pool, QC graphs, instrument calibration, reagents, and any special considerations are submitted to NCHS quarterly. The reports are reviewed for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.

All QC procedures recommended by the manufacturers were followed. Reported results for all assays meet the Division of Laboratory Sciences’ quality control and quality assurance performance criteria for accuracy and precision, similar to the Westgard rules (Caudill, et al. 2008).

Data Processing and Editing

The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.

Analytic Notes

Refer to the 2005-2006 Laboratory Data Overview for general information on NHANES laboratory data.

Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for details on the use of sample weights and analytic issues.

Subsample Weights

The original pooled-sample weight created for this file released in July 2013 was not correctly stratified to the U.S population total. This new file contains the corrected sample weight (WTSMSMPA). No changes or corrections were made to the lab analyte data in this new release. Any analyses of the data using the old public use data file should be repeated using the corrected sample weight on this file.

PBDEs and PBB-153 were measured in a one third subsample of persons 12 years and over, and samples were pooled in groups of 8 samples per pool within 32 demographic groups. The analysis of NHANES 2005-2006 pooled-sample data must be conducted with the basic demographic variables provided in this data file. This pooled-sample data file cannot be linked to other NHANES 2005-2006 data.  Because each sample person does not have an equal probability of selection, sample weighting is needed to produce correct population estimates of means, percentiles, and other descriptive statistics.

The pooled-sample weights required to produce estimates from these data are included in this data file. The analysis of pooled-samples from survey data is a relatively new field of study, and there is currently no established method to produce variance estimates for these pooled results. These data cannot be analyzed using software designed for complex surveys because design features are not available. 

Rationale and Methods Used to Create Pooled Results

The Centers for Disease Control and Prevention (CDC) provide an ongoing assessment of the US population's exposure to environmental chemicals by using biomonitoring in conjunction with CDC's National Health and Nutrition Examination Survey (NHANES). Characterizing the distributions of concentrations of environmental compounds or their metabolites in the US population is a primary objective of CDC's biomonitoring program. Historically, this characterization has been based on individual measurements of these compounds in body fluid or tissue from representative samples of the population. Pooling samples allows for larger sample volumes, which can result in lower limits of detection and reduces the number of measurements and costs. For the first time in NHANES 2005-2006, a weighted pooled-sample design was implemented to facilitate pooling samples before making analytical measurements (pooled results were not weighted in NHANES 2001-2002). Table 1 lists the IUPAC (International Union of Pure and Applied Chemistry (IUPAC) names, common abbreviation, and NHANES variable name for the analytes included in this data file.

Pools were prepared from serum collected from a random one-third subset of the NHANES 2005–2006 participants aged 12 years and older. Samples were pooled based on gender, race and Hispanic origin, and age. To implement the pooled-sample design, each participant sample was identified as belonging to one of 32 demographic groups based on race and Hispanic origin (non-Hispanic white: NHW, non-Hispanic black: NHB, Mexican American: MA,: not non-Hispanic black, non-Hispanic white or Mexican-American: OTHER), gender (Male, Female), and age group (12-19, 20-39, 40-59, and 60+ years of age and older). Eight (8) samples were included in each pool. The number of pools created for each of the 32 demographic groups varied depending on the total number of individual samples available in a demographic group. The one-third subset of NHANES 2005-2006 represents 2345 individual samples, but because the pooled-sample design requires that all samples be of sufficient volume and that there be the same number of samples in each pool, only 1973 samples were available to create 247 pools with 8 samples per pool.  See more details on pool sample formation and exceptions in Table 2. The variable SAMPLEID denotes the identification number for each pool and ranges from 1 through 247. Please refer to the Pooled-Sample Technical Support file (POOLTF_D) for detailed information on individual participants included in each pool.

In order to incorporate sample weighting into the pooled-sample design it was necessary to use a different volume of material from each sample contributing to a pool. The volume chosen for each sample in a pool was based on the ratio of its sampling weight to the sum of the sampling weights of all samples in the pool. To physically accomplish the pooling in the laboratory required that the ratio of the largest to the smallest sampling weight of samples in the same pool be no larger than about 4 or 5. The individual samples were sorted/stratified by sampling weight within each of the 32 demographic groups and pools were formed using samples with sampling weights adjacent to one another in the sorted list. The number of samples in the one-third subset, 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 2. Once the pools were created, summed sampling weights were further adjusted to account for the unused samples. These adjusted summed sampling weights are represented by the variable named WTSMSMPA.

Detection Limits

In the dataset, the whole weight detection limit (ng/g serum) is a variable and dependent on the available sample size, however, the variation in sample size was low. Three variables are provided for each of these analytes.  The variable name ending in “LC” (ex., LBDBHCLC) indicates whether the result was below the limit of detection: the value “0” means that the result was at or above the limit of detection, “1” indicates that the result was below the limit of detection.  The varibale ending in “LA” (ex., LBCBHCLA) is the lipid adjusted detection limits in ng/g lipid, because the lipid levels are measured in individual pools/specimens.  The third variable prefixed LBC (ex., LBCBHC) provides the analytic result for that analyte.  For analytes with analytic results below the lower limit of detection (ex., LBDBHCLC= 1), an imputed fill value was placed in the analyte results field. This value is the lower limit of detection divided by the square root of 2 (LLOD/sqrt[2]). The lower limit of detection (LLOD in ng/g serum and ng/g lipid) for PST: 

Table 1. NHANES Variable name, common abbreviation and International Union of Pure and Applied Chemistry (IUPAC) name for each analyte reported. Maximum limit of detection (MLOD) expressed as ng/g serum and ng/g lipid). 

Variable Name Common Abbrev. IUPAC Name Max LOD (ng/g serum) Max LOD (ng/g lipid)
LBCHCB HCB Hexachlorobenzene 0.0134 2.72
LBCBHC B-HCCH BETA-Hexachlorocyclohexane 0.0056 1.02
LBCGHC G-HCCH GAMA-Hexachlorocyclohexane (Lindane) 0.0056 1.03
LBCOXY OXYCHLOR Oxychlordane 0.0045 0.85
LBCTNA T-NONA Trans-Nonachlor 0.0023 0.45
LBCPDE PP-DDE 2,2-Bis(4-chlorophenyl)-1,1-dichloroethene 0.0023 0.45
LBCPDT PP-DDT 2,2-Bis(4-chlorophenyl-1,1,1-trichloroethan 0.0045 0.88
LBCMIR MIREX Mirex 0.0056 1.03

Table 2.  Number of subjects per demographic group in the NHANES 2005–2006 one-third subsample, number of individual serum samples available, number of usable samples, and number of pools formed from usable samples.

 Table 2.  Number of subjects per demographic group in the NHANES 2005–2006 one-third subsample, number of individual serum samples available, number of usable samples, and number of pools formed from usable samples.

1 Value of this categorical variable in the data set.
2 With only 23 usable samples, two 8 sample pools and one 7 sample pool were created.
3 With only 6 usable samples, one 6 sample pool was created. 
 
 
Methodological Considerations for analysis

There are a few pooled-sample methodological publications which address issues related to the following topics (See References.)

• Variance estimation and bias correction when pooling samples from log-normally distributed populations (Caudill, 2010a; Caudill, 2010b; Caudill et al., 2007);
• Models that incorporate measurement error when analyzing pooled-samples from normally or log-normally distributed populations (Caudill, 2010a);
• Incorporation of sample weighting into a pooled-sample design (Caudill, 2012; Caudill, 2010a);
• Estimation of standard errors and confidence limits for point estimates from pooled-samples (Caudill, 2012; Caudill, 2010a).

References

Codebook and Frequencies

SAMPLEID - Pool identification number

Variable Name:
SAMPLEID
SAS Label:
Pool identification number
English Text:
Pool identification number
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 to 247 Range of Values 247 247
. Missing 0 247

RIAGENDR - Gender

Variable Name:
RIAGENDR
SAS Label:
Gender
English Text:
Gender
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Male 114 114
2 Female 133 247
. Missing 0 247

ETHNICTY - Ethnicity - Recode

Variable Name:
ETHNICTY
SAS Label:
Ethnicity - Recode
English Text:
Ethnicity - Recode
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Non-Hispanic White 104 104
2 Non-Hispanic Black 62 166
3 Mexican American 62 228
4 Other 19 247
. Missing 0 247

RIDAGGRP - Age group

Variable Name:
RIDAGGRP
SAS Label:
Age group
English Text:
Age group
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 12-19 years 78 78
2 20-39 years 66 144
3 40-59 years 52 196
4 60+ years 51 247
. Missing 0 247

RIANSMP - Number of samples in a pool

Variable Name:
RIANSMP
SAS Label:
Number of samples in a pool
English Text:
Number of samples in a pool
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
6 to 8 Range of Values 247 247
. Missing 0 247

WTSMSMPA - Adjust sum sampling weights in same pool

Variable Name:
WTSMSMPA
SAS Label:
Adjust sum sampling weights in same pool
English Text:
Adjust sum sampling weights in same pool
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
59702.062036 to 3228037.3031 Range of Values 247 247
. Missing 0 247

LBCBHC - Beta-hexachlorocyclohexane (pg/g)

Variable Name:
LBCBHC
SAS Label:
Beta-hexachlorocyclohexane (pg/g)
English Text:
Beta-hexachlorocyclohexane (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.004 to 2.3147 Range of Values 247 247
. Missing 0 247

LBCBHCLA - B-hexachlorocyclohexane Lipid Adj (ng/g)

Variable Name:
LBCBHCLA
SAS Label:
B-hexachlorocyclohexane Lipid Adj (ng/g)
English Text:
B-hexachlorocyclohexane Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.51 to 294 Range of Values 247 247
. Missing 0 247

LBDBHCLC - Beta-hexachlorocyclohexane comment code

Variable Name:
LBDBHCLC
SAS Label:
Beta-hexachlorocyclohexane comment code
English Text:
Beta-hexachlorocyclohexane comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 186 186
1 Below lower detection limit 61 247
. Missing 0 247

LBCGHC - Gamma-hexachlorocyclohexane (pg/g)

Variable Name:
LBCGHC
SAS Label:
Gamma-hexachlorocyclohexane (pg/g)
English Text:
Gamma-hexachlorocyclohexane (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.004 to 0.0056 Range of Values 247 247
. Missing 0 247

LBCGHCLA - G-hexachlorocyclohexane Lipid Adj (ng/g)

Variable Name:
LBCGHCLA
SAS Label:
G-hexachlorocyclohexane Lipid Adj (ng/g)
English Text:
G-hexachlorocyclohexane Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.42 to 1.03 Range of Values 247 247
. Missing 0 247

LBDGHCLC - Gamma-hexachlorocyclohexane comment code

Variable Name:
LBDGHCLC
SAS Label:
Gamma-hexachlorocyclohexane comment code
English Text:
Gamma-hexachlorocyclohexane comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 0 0
1 Below lower detection limit 247 247
. Missing 0 247

LBCHCB - Hexachlorobenzene (pg/g)

Variable Name:
LBCHCB
SAS Label:
Hexachlorobenzene (pg/g)
English Text:
Hexachlorobenzene (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.0125 to 0.1967 Range of Values 247 247
. Missing 0 247

LBCHCBLA - Hexachlorobenzene Lipid Adj (ng/g)

Variable Name:
LBCHCBLA
SAS Label:
Hexachlorobenzene Lipid Adj (ng/g)
English Text:
Hexachlorobenzene Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
2.15 to 23.95 Range of Values 247 247
. Missing 0 247

LBDHCBLC - Hexachlorobenzene comment code

Variable Name:
LBDHCBLC
SAS Label:
Hexachlorobenzene comment code
English Text:
Hexachlorobenzene comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 244 244
1 Below lower detection limit 3 247
. Missing 0 247

LBCMIR - Mirex (pg/g)

Variable Name:
LBCMIR
SAS Label:
Mirex (pg/g)
English Text:
Mirex (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.004 to 0.3722 Range of Values 247 247
. Missing 0 247

LBCMIRLA - Mirex Lipid Adj (ng/g)

Variable Name:
LBCMIRLA
SAS Label:
Mirex Lipid Adj (ng/g)
English Text:
Mirex Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.47 to 61.01 Range of Values 247 247
. Missing 0 247

LBDMIRLC - Mirex comment code

Variable Name:
LBDMIRLC
SAS Label:
Mirex comment code
English Text:
Mirex comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 147 147
1 Below lower detection limit 100 247
. Missing 0 247

LBCODT - o,p'-DDT (pg/g)

Variable Name:
LBCODT
SAS Label:
o,p'-DDT (pg/g)
English Text:
o,p'-DDT (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.004 to 0.0722 Range of Values 247 247
. Missing 0 247

LBCODTLA - o,p'-DDT Lipid Adj (ng/g)

Variable Name:
LBCODTLA
SAS Label:
o,p'-DDT Lipid Adj (ng/g)
English Text:
o,p'-DDT Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.42 to 13.67 Range of Values 247 247
. Missing 0 247

LBDODTLC - o,p'-DDT comment code

Variable Name:
LBDODTLC
SAS Label:
o,p'-DDT comment code
English Text:
o,p'-DDT comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 62 62
1 Below lower detection limit 185 247
. Missing 0 247

LBCOXY - Oxychlordane (pg/g)

Variable Name:
LBCOXY
SAS Label:
Oxychlordane (pg/g)
English Text:
Oxychlordane (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.0041 to 0.5763 Range of Values 247 247
. Missing 0 247

LBCOXYLA - Oxychlordane Lipid Adj (ng/g)

Variable Name:
LBCOXYLA
SAS Label:
Oxychlordane Lipid Adj (ng/g)
English Text:
Oxychlordane Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.65 to 94.12 Range of Values 247 247
. Missing 0 247

LBDOXYLC - Oxychlordane comment code

Variable Name:
LBDOXYLC
SAS Label:
Oxychlordane comment code
English Text:
Oxychlordane comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 241 241
1 Below lower detection limit 6 247
. Missing 0 247

LBCPDE - p,p'-DDE (pg/g)

Variable Name:
LBCPDE
SAS Label:
p,p'-DDE (pg/g)
English Text:
p,p'-DDE (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.2614 to 69.7606 Range of Values 247 247
. Missing 0 247

LBCPDELA - p,p'-DDE Lipid Adj (ng/g)

Variable Name:
LBCPDELA
SAS Label:
p,p'-DDE Lipid Adj (ng/g)
English Text:
p,p'-DDE Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
53.47 to 13200 Range of Values 247 247
. Missing 0 247

LBDPDELC - p,p'-DDE comment code

Variable Name:
LBDPDELC
SAS Label:
p,p'-DDE comment code
English Text:
p,p'-DDE comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 247 247
1 Below lower detection limit 0 247
. Missing 0 247

LBCPDT - p,p'-DDT (pg/g)

Variable Name:
LBCPDT
SAS Label:
p,p'-DDT (pg/g)
English Text:
p,p'-DDT (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.0042 to 3.5924 Range of Values 247 247
. Missing 0 247

LBCPDTLA - p,p'-DDT Lipid Adj (ng/g)

Variable Name:
LBCPDTLA
SAS Label:
p,p'-DDT Lipid Adj (ng/g)
English Text:
p,p'-DDT Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.85 to 680 Range of Values 247 247
. Missing 0 247

LBDPDTLC - p,p'-DDT comment code

Variable Name:
LBDPDTLC
SAS Label:
p,p'-DDT comment code
English Text:
p,p'-DDT comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 245 245
1 Below lower detection limit 2 247
. Missing 0 247

LBCTNA - trans-Nonachlor (pg/g)

Variable Name:
LBCTNA
SAS Label:
trans-Nonachlor (pg/g)
English Text:
trans-Nonachlor (pg/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.0023 to 0.8988 Range of Values 247 247
. Missing 0 247

LBCTNALA - trans-Nonachlor Lipid Adj (ng/g)

Variable Name:
LBCTNALA
SAS Label:
trans-Nonachlor Lipid Adj (ng/g)
English Text:
trans-Nonachlor Lipid Adj (ng/g)
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.45 to 138 Range of Values 247 247
. Missing 0 247

LBDTNALC - trans-Nonachlor comment code

Variable Name:
LBDTNALC
SAS Label:
trans-Nonachlor comment code
English Text:
trans-Nonachlor comment code
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 246 246
1 Below lower detection limit 1 247
. Missing 0 247