Table of Contents

Locator Record

Title: Polyfluoroalkyl Chemicals (Pooled Samples) (PFC_Pool )
Contact Number: 1-866-441-NCHS
Years of Content: 2001 - 2002
First Published: October, 2008
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:olyfluoroalkyl compounds
Record Source: NHANES 2001 - 2002
Survey Methodology: NHANES 2001 - 2002 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

Component Description

The primary objective of this study was to characterize serum concentrations of selected polyfluoroalkyl chemicals (PFCs) in pooled serum samples collected from children 3-11 years old participants in NHANES 2001-2002.

PFCs have been used extensively since the 1950s in commercial applications, including surfactants, lubricants, paper and textile coatings, polishes, food packaging, and fire-retarding foams. Some of these PFCs, including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), persist in humans and the environment and have been detected worldwide in wildlife. Because of the known animal toxicity of several PFCs; their ubiquitous presence; and their persistence in humans, wildlife, and the environment, PFCs research is of interest. Biomonitoring data for these PFCs in the general population are needed to assess human exposures to these compounds.

By using a modification of an existing analytical method (Kuklenyik et al. 2005), the following 11 PFCs were measured: perfluorooctane sulfonamide (PFOSA), 2-(N-ethyl-perfluorooctane sulfonamido) acetic acid (Et-PFOSA-AcOH), 2-(N-methyl-perfluorooctane sulfonamido) acetic acid (Me-PFOSA-AcOH), perfluorobutane sulfonic acid (PFBuS), perfluorohexane sulfonic acid (PFHxS), PFOS, perfluoroheptanoic acid (PFHpA), PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDeA), and perfluorododecanoic acid (PFDoA).

Eligible Sample

Study participants aged 3-11 years from of 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. The eleven PFCs were measured by using on-line solid-phase extraction (SPE) coupled to isotope dilution-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The following isotope-labeled internal standards were used for quantification: 18O2-PFOS (PFOS, PFBuS and PFHxS), 13C2-PFOA (PFOA, PFHpA), 13C5-PFNA (PFNA), 13C2-PFDeA (PFDeA and PFDoA), 18O2-PFOSA (PFOSA), D3-Me-PFOSA-AcOH (Me-PFOSA-AcOH), and D5-Et-PFOSA-AcOH (Et-PFOSA-AcOH). Briefly, 0.25 mL of 0.1 M formic acid and 0.025 mL of internal standard solution were added to 0.1 mL of serum, and the spiked serum was voltex-mixed and sonicated. The samples were placed on a commercial Symbiosis on-line SPE system (Spark Holland, Plainsboro, NJ) for the preconcentration of the analytes on a Polaris C18 cartridge (7 μm, 10 × 1 mm; Spark Holland). The analytes were transferred onto a Betasil C8 HPLC column (3 × 50 mm, 5 μm; ThermoHypersil Keystone, Bellefonte, PA), separated by HPLC (mobile phase A: 20 mM ammonium acetate in water, pH = 4; mobile phase B: methanol), and detected by negative-ion TurboIonspray-MS/MS on an API 4000 mass spectrometer (Applied Biosystems, Foster City, CA). The limits of detection ranged from 0.1 ng/mL to 0.4 ng/mL.

Data Processing and Editing

Specimens were processed, stored, and shipped to DLS, NCEH, CDC (Atlanta, Georgia). The analytical approach used, including data processing, was a modification of a method described in detail in a peer-reviewed publication (Kuklenyik et al. 2005). 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

CDC’s laboratory is CLIA ‘88 certified and practices all quality control (QC) and assurance procedures dictated by this certification. QC procedures included the daily analysis of characterized serum pools and the periodic analysis of proficiency testing materials. Low-concentration (QCL; ~3 ng/mL to ~9 ng/mL, depending upon the analyte) and high-concentration (QCH; ~10 ng/mL to ~30 ng/mL, depending upon the analyte) QC materials were prepared from a base calf serum pool, dispensed in 3-mL aliquots and stored at −20 °C. QC materials were characterized through repeated measurements spanning at least 3 weeks, to define the mean concentrations and the 95% and 99% control limits of PFCs. Calibration standards, 2 QCH, 2 QCL, reagent and serum blanks were analyzed with the samples. The concentrations of the two QCH and the two QCL were averaged to obtain one measurement of QCH and of QCL per batch; these concentrations were evaluated using standard statistical probability rules.

Analytic Notes

To prepare the pools, residual serum, collected from the 3–11 year old NHANES 2001–2002 participants and previously analyzed for cotinine, a marker of environmental tobacco smoke, was used. 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). 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. All pools included 21 (3–5 year old) or 57 (6–11 year old) individual samples randomly selected.

The limits of detection (LODs) were 0.1 ng/mL (PFOSA, PFBuS, PFHxS, PFOA, and PFNA), 0.2 ng/mL (PFOS, Me-PFOSA-AcOH, Et-PFOSA-AcOH, PFDeA, PFUA, and PFDoA), and 0.4 ng/mL (PFHpA). The detection limit divided by the square root of 2 is the value provided for results that are below the limit of detection.

Variables

PFCANA
Et-PFOS-A, 2-(N-ethyl-perfluorooctane sulfonamido) acetic acid
Me-PFOS-A, 2-(N-methyl-perfluorooctane sulfonamido) acetic acid
PFBuS, perfluorobutane sulfonic acid
PFDeA, perfluorodecanoic acid
PFDoA, perfluorododecanoic acid
PFHpA, perfluoroheptanoic acid
PFHxS, perfluorohexane sulfonic acid
PFNA, perfluorononanoic acid
PFOA, perfluorooctanoic acid
PFOS, perfluorooctane sulfonic acid
PFOSA, perfluorooctane sulfonamide

PFCRACE
1= non-Hispanic white
2=non-Hispanic white
3=Hispanic

PFCGENDER
1=male
2=female

PFCAGE
3= 2-5 years
6= 6-11 years

PFCPOOL
1=Pool#1
2=Pool#2

PFCMNT
0= at or above the detection limit
1=below the detection limit

Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues.

References

Codebook and Frequencies

PFCANA - Analyte Abbreviated Name

Variable Name:
PFCANA
SAS Label:
Analyte Abbreviated Name
English Text:
Analyte Abbreviated Name
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
< blank > Missing 0 0

PFCRACE - Race

Variable Name:
PFCRACE
SAS Label:
Race
English Text:
Race
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 non-Hispanic white 88 88
2 non-Hispanic black 88 176
3 Hispanic 88 264
. Missing 0 264

PFCGENDR - Gender

Variable Name:
PFCGENDR
SAS Label:
Gender
English Text:
Gender
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 male 132 132
2 female 132 264
. Missing 0 264

PFCAGE - Age

Variable Name:
PFCAGE
SAS Label:
Age
English Text:
Age
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3 3-5 years 132 132
6 6-11 years 132 264
. Missing 0 264

PFCPOOL - Pool Number

Variable Name:
PFCPOOL
SAS Label:
Pool Number
English Text:
Pool Number
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Pool #1 132 132
2 Pool #2 132 264
. Missing 0 264

PFCAMNT - Amount (ng/ml)

Variable Name:
PFCAMNT
SAS Label:
Amount (ng/ml)
English Text:
Amount (ng/ml)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.1 to 52.4 Range of Values 264 264
. Missing 0 264

PFCCMT - Comment Code

Variable Name:
PFCCMT
SAS Label:
Comment Code
English Text:
Comment Code
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 at or above the detection limit 195 195
1 below the detection limit 69 264
. Missing 0 264