Table of Contents

Component Description

Exposure data to perfluoroalkyl and polyfluoroalkyl substances (PFAS) among the US general population 12 years of age and older have been included in the National Health and Nutrition Examination Survey (NHANES) since 1999-2000 (CDC 2015). However, general population data among children 3-11 years of age are limited to those obtained from using pooled sera collected in NHANES 2001-2002 (Kato et al. 2009).

Exposure data in children may impact health later in life and, therefore, are of public health significance. However, data on general exposure to PFAS among American children younger than 12 years do not exist in NHANES using individual samples. To fill this exposure data gap, we measured fourteen PFAS in one third subset of participants 3-11 years of age using surplus sera collected for the measurement of cotinine as part of NHANES 2013-2014.

Eligible Sample

Participants aged 3-11 years from NHANES 2013-2014 with stored serum.

Description of Laboratory Methodology

Solid phase extraction coupled to High Performance Liquid Chromatography-Turbo Ion Spray ionization-tandem Mass Spectrometry (online SPE-HPLC-TIS-MS/MS) is used for the quantitative detection of 14 PFAS: perfluorooctane sulfonamide (PFOSA), 2-(N-methyl-perfluorooctane sulfonamido) acetic acid (Me-PFOSA-AcOH), 2-(N-ethyl-perfluorooctane sulfonamido) acetic acid (Et-PFOSA-AcOH), perfluorobutane sulfonate (PFBuS), perfluorohexane sulfonate (PFHxS), perfluoroheptanoate (PFHpA), perfluorononanoate (PFNA), perfluorodecanoate (PFDeA), perfluoroundecanoate (PFUA), perfluorododecanoate (PFDoA), linear PFOA (n-PFOA), sum of branched isomers of PFOA (Sb-PFOA), linear PFOS (n-PFOS), and sum of perfluoromethylheptane sulfonate isomers (Sm-PFOS). Briefly, after dilution with formic acid, one aliquot of 50 μL of serum is injected into a commercial column switching system allowing for concentration and chromatographic separation of the analytes. Detection and quantification are done using tandem mass spectrometry (Kato, et al. 2011).

Refer to the Laboratory Method Files section for detailed laboratory procedure manual(s) of the methods used.

They were no changes to the lab equipment or lab site for this component compared with those used for measuring PFAS in participants 12 years of age and older in NHANES 2013-2014.

To estimate the total (sum of the isomers measured) concentrations of PFOS and PFOA for each participant, sum the concentrations of n-PFOA and Sb-PFOA for PFOA, and those of n-PFOS and Sm-PFOS for PFOS. If the value of one isomer is less than the limit of detection (LOD), then the imputed value is used. The imputed value is calculated as the LOD divided by the square root of 2 (Hornung et al. 1990) and imputed values are provided in the NHANES public release file. If the values of all isomers are reported as less than the LOD, then the sum will be the sum of each imputed value.

Laboratory Quality Assurance and Monitoring

The analytical measurements were conducted following strict quality control/quality assurance CLIA guidelines. Along with the study samples, each analytical run included high- and low-concentration quality control materials (QCs) and serum blanks to assure the accuracy and reliability of the data. The concentrations of the high-concentration QCs and the low-concentration QCs, averaged to obtain one measurement of high-concentration QC and low-concentration QC for each run, were evaluated using standard statistical probability rules (Caudill et al. 2008).

Data Processing and Editing

Data were received after all analyses were complete. The data were not edited.
Data Access: All data are publicly available.

Analytic Notes

Refer to the 2013-2014 Laboratory Data Overview for general information on NHANES laboratory data.

Subsample weights

Fourteen PFAS were measured in a one third subsample of persons 3-11 years of age. Special sample weights, included in this data file, are required to analyze these data properly.

Demographic and Other Related Variables

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 2013-2014 Demographic Data File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.
This laboratory data file can be linked to other NHANES data files using the unique survey participant identifier (i.e., SEQN).

Detection Limits

Detection limits were constant for all of the analytes in the data set. Two variables are provided for each analyte.
The variable name ending in “L” (ex., SSPFOAL) 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. For analytes with results below the lower limit of detection (ex., SSPFOAL=1), an imputed fill value was placed in the results field. This value is the lower limit of detection divided by square root of 2 (LLOD/sqrt2).
The other variable prefixed SS (ex., SSNPFOA) provides the analytic result for each analyte.
The lower limit of detection (LLOD, in ng/mL) for the fourteen PFAS are:

Variable Name

SAS Label

LLOD

SSPFSA

Perfluorooctane sulfonamide (ng/mL)

0.10

SSMPAH

2-(N-methyl-perfluorooctane sulfonamido) acetic acid (ng/mL)

0.10

SSEPAH

2-(N-ethyl-perfluorooctane sulfonamido) acetic acid (ng/mL)

0.10

SSPFDE

Pefluorodecanoic acid (ng/mL)

0.10

SSPFBS

Perfluorobutane sulfonic acid (ng/mL)

0.10

SSPFHP

Perfluoroheptanoic acid (ng/mL)

0.10

SSPFNA

Perfluorononanoic acid (ng/mL)

0.10

SSPFUA

Perfluoroundecanoic acid (ng/mL)

0.10

SSPFDO

Perflurododecanoic acid (ng/mL)

0.10

SSPFHS

Perfluorohexane sulfonic acid (ng/mL)

0.10

SSNPFOA

Linear perfluorooctanoate (ng/mL)

0.10

SSBPFOA

Branched isomers of perfluorooctanoate (ng/mL)

0.10

SSNPFOS

Linear perfluorooctane sulfonate (PFOS) (ng/mL)

0.10

SSMPFOS

Monomethyl branched isomers of PFOS (ng/mL)

0.10

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


References

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 3 YEARS - 11 YEARS

SSPFSA - Perfluorooctane sulfonamide (ng/mL)

Variable Name:
SSPFSA
SAS Label:
Perfluorooctane sulfonamide (ng/mL)
English Text:
Perfluorooctane sulfonamide (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.72 Range of Values 639 639
. Missing 0 639

SSPFSAL - Perfluorooctane sulfonam Cmt code

Variable Name:
SSPFSAL
SAS Label:
Perfluorooctane sulfonam Cmt code
English Text:
Perfluorooctane sulfonam Cmt 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 21 21
1 Below lower detection limit 618 639
. Missing 0 639

SSMPAH - 2(N-methyl-perfluor sulfon) acid (ng/mL)

Variable Name:
SSMPAH
SAS Label:
2(N-methyl-perfluor sulfon) acid (ng/mL)
English Text:
2(N-methyl-perfluor sulfon)acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 6.75 Range of Values 639 639
. Missing 0 639

SSMPAHL - 2(N-methyl-perfluor sulfon) acid Cmt cd

Variable Name:
SSMPAHL
SAS Label:
2(N-methyl-perfluor sulfon) acid Cmt cd
English Text:
2(N-methyl-perfluor sulfon)ac.acid Cmt cd
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 303 303
1 Below lower detection limit 336 639
. Missing 0 639

SSEPAH - 2(N-ethyl-perfluor sulfon) acid (ng/mL)

Variable Name:
SSEPAH
SAS Label:
2(N-ethyl-perfluor sulfon) acid (ng/mL)
English Text:
2(N-ethyl-perfluor sulfon)ac.acid(ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.49 Range of Values 639 639
. Missing 0 639

SSEPAHL - 2(N-ethyl-perfluor sulfon) acid Cmt cd

Variable Name:
SSEPAHL
SAS Label:
2(N-ethyl-perfluor sulfon) acid Cmt cd
English Text:
2(N ethyl-perfluor sulfon)ac.acid Cmt cd
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 15 15
1 Below lower detection limit 624 639
. Missing 0 639

SSPFDE - Pefluorodecanoic acid (ng/mL)

Variable Name:
SSPFDE
SAS Label:
Pefluorodecanoic acid (ng/mL)
English Text:
Pefluorodecanoic acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 2 Range of Values 639 639
. Missing 0 639

SSPFDEL - Pefluorodecanoic acid Cmt code

Variable Name:
SSPFDEL
SAS Label:
Pefluorodecanoic acid Cmt code
English Text:
Pefluorodecanoic acid (ng/mL) Cmt 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 300 300
1 Below lower detection limit 339 639
. Missing 0 639

SSPFBS - Perfluorobutane sulfonic acid (ng/mL)

Variable Name:
SSPFBS
SAS Label:
Perfluorobutane sulfonic acid (ng/mL)
English Text:
Perfluorobutane sulfonic acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.17 Range of Values 639 639
. Missing 0 639

SSPFBSL - Perfluorobutane sulfonic acid Cmt code

Variable Name:
SSPFBSL
SAS Label:
Perfluorobutane sulfonic acid Cmt code
English Text:
Perfluorobutane sulfonic acid Cmt 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 27 27
1 Below lower detection limit 612 639
. Missing 0 639

SSPFHP - Perfluoroheptanoic acid (ng/mL)

Variable Name:
SSPFHP
SAS Label:
Perfluoroheptanoic acid (ng/mL)
English Text:
Perfluoroheptanoic acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.97 Range of Values 639 639
. Missing 0 639

SSPFHPL - Perfluoroheptanoic acid Cmt code

Variable Name:
SSPFHPL
SAS Label:
Perfluoroheptanoic acid Cmt code
English Text:
Perfluoroheptanoic acid Cmt 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 124 124
1 Below lower detection limit 515 639
. Missing 0 639

SSPFNA - Perfluorononanoic acid (ng/mL)

Variable Name:
SSPFNA
SAS Label:
Perfluorononanoic acid (ng/mL)
English Text:
Perfluorononanoic acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 52.92 Range of Values 639 639
. Missing 0 639

SSPFNAL - Perfluorononanoic acid Cmt code

Variable Name:
SSPFNAL
SAS Label:
Perfluorononanoic acid Cmt code
English Text:
Perfluorononanoic acid Cmt 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 638 638
1 Below lower detection limit 1 639
. Missing 0 639

SSPFUA - Perfluoroundecanoic acid (ng/mL)

Variable Name:
SSPFUA
SAS Label:
Perfluoroundecanoic acid (ng/mL)
English Text:
Perfluoroundecanoic acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 2.83 Range of Values 639 639
. Missing 0 639

SSPFUAL - Perfluoroundecanoic acid Cmt cd

Variable Name:
SSPFUAL
SAS Label:
Perfluoroundecanoic acid Cmt cd
English Text:
Perfluoroundecanoic acid Cmt cd
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 208 208
1 Below lower detection limit 431 639
. Missing 0 639

SSPFDO - Perflurododecanoic acid (ng/mL)

Variable Name:
SSPFDO
SAS Label:
Perflurododecanoic acid (ng/mL)
English Text:
Perflurododecanoic acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 639 639
. Missing 0 639

SSPFDOL - Perflurododecanoic acid Cmt code

Variable Name:
SSPFDOL
SAS Label:
Perflurododecanoic acid Cmt code
English Text:
Perflurododecanoic acid Cmt 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 0 0
1 Below lower detection limit 639 639
. Missing 0 639

SSPFHS - Perfluorohexane sulfonic acid (ng/mL)

Variable Name:
SSPFHS
SAS Label:
Perfluorohexane sulfonic acid (ng/mL)
English Text:
Perfluorohexane sulfonic acid (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 12.9 Range of Values 639 639
. Missing 0 639

SSPFHSL - Perfluorohexane sulfonic acid Cmt code

Variable Name:
SSPFHSL
SAS Label:
Perfluorohexane sulfonic acid Cmt code
English Text:
Perfluorohexane sulfonic acid Cmt 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 638 638
1 Below lower detection limit 1 639
. Missing 0 639

SSNPFOA - Linear perfluorooctanoate (ng/mL)

Variable Name:
SSNPFOA
SAS Label:
Linear perfluorooctanoate (ng/mL)
English Text:
Linear perfluorooctanoate (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 8.22 Range of Values 639 639
. Missing 0 639

SSNPFOAL - Linear perfluorooctanoate Cmt Code

Variable Name:
SSNPFOAL
SAS Label:
Linear perfluorooctanoate Cmt Code
English Text:
Linear perfluorooctanoate Cmt 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 638 638
1 Below lower detection limit 1 639
. Missing 0 639

SSBPFOA - Branch isomers-perfluorooctanoate(ng/mL)

Variable Name:
SSBPFOA
SAS Label:
Branch isomers-perfluorooctanoate(ng/mL)
English Text:
Branch isomers-perfluorooctanoate (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.69 Range of Values 639 639
. Missing 0 639

SSBPFOAL - Branch isomers-perfluorooctanoate Cmt cd

Variable Name:
SSBPFOAL
SAS Label:
Branch isomers-perfluorooctanoate Cmt cd
English Text:
Branch isomers-perfluorooctanoate Cmt cd
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 163 163
1 Below lower detection limit 476 639
. Missing 0 639

SSNPFOS - Linear perfluorooctane sulfonate (ng/mL)

Variable Name:
SSNPFOS
SAS Label:
Linear perfluorooctane sulfonate (ng/mL)
English Text:
Linear perfluorooctane sulfonate( ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.5 to 26.54 Range of Values 639 639
. Missing 0 639

SSNPFOSL - Linear perfluorooctane sulfonate cmt cd

Variable Name:
SSNPFOSL
SAS Label:
Linear perfluorooctane sulfonate cmt cd
English Text:
Linear perfluorooctane sulfonate cmt cd
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 639 639
1 Below lower detection limit 0 639
. Missing 0 639

SSMPFOS - Monomethyl br. isomers of PFOS (ng/mL)

Variable Name:
SSMPFOS
SAS Label:
Monomethyl br. isomers of PFOS (ng/mL)
English Text:
Monomethyl br. isomers of PFOS (ng/mL)
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.18 to 10.68 Range of Values 639 639
. Missing 0 639

SSMPFOSL - Monomethyl br. isomers of PFOS cmt cd

Variable Name:
SSMPFOSL
SAS Label:
Monomethyl br. isomers of PFOS cmt cd
English Text:
Monomethyl br. isomers of PFOS cmt cd
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 639 639
1 Below lower detection limit 0 639
. Missing 0 639

WTSS2YR - SS 3-11 year old subsample wt

Variable Name:
WTSS2YR
SAS Label:
SS 3-11 year old subsample wt
English Text:
Surplus specimen 3-11 years old subsample weight
Target:
Both males and females 3 YEARS - 11 YEARS
Code or Value Value Description Count Cumulative Skip to Item
12849.506491 to 365955.18816 Range of Values 639 639
. Missing 0 639