Table of Contents

Component Description

Exposure data to per-and polyfluoroalkyl substances (PFAS) among the U.S. general population have been included in the National Health and Nutrition Examination Survey (NHANES) since 1999-2000 (CDC 2018). Several long-chain PFAS, including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been frequently detected at trace levels in the blood of NHANES participants, while short-chain PFAS (e.g., perfluorobutane sulfonic acid, perfluoroheptanoic acid) have not (CDC 2018). The lower detection frequencies and concentration ranges may reflect lower exposure to short-chain PFAS than to PFOS or PFOA or that, in humans, short-chain PFAS efficiently eliminate in urine. However, PFAS have not been measured in the urine of NHANES participants.

Because of changes in the manufacturing and environmental emissions of long-alkyl chain PFAS since the early 2000s, PFAS with shorter alkyl chains, and fluorinated alternatives, including perfluoroalkyl ether carboxylic acids (PFECAs) and perfluoroalkyl ether sulfonic acids have entered the market (Gordon 2011, Wang et al. 2013), and the environment (Xiao 2017). Two PFECAs, GenX (ammonium salt of 2,3,3,3,-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate]) and ADONA (ammonium salt of 4,8-dioxa-3H-perfluorononanoate [DONA]), have shorter elimination half-lives in animals than PFOA (Gannon et al. 2016). The detection of GenX in surface waters and drinking water (Heydebreck et al. 2015, Sun et al. 2016) has raised concerns about potential health implications from human exposure to PFECAs through contaminated drinking water. Exposure data to alternative PFAS in the U.S. general population do not exit.

To fill these exposure data gaps, we measured seventeen PFAS, including three fluorinated alternatives used as PFOA or PFOS replacements, in one-third subsample of participants 6+ years of age using surplus urine collected for the measurement of select personal care product chemicals as part of NHANES 2013-2014.

Eligible Sample

One-third subsample of participants aged 6+ years from NHANES 2013-2014 with stored urine (N=2682).

Description of Laboratory Methodology

We used solid phase extraction coupled to high performance liquid chromatography-tandem mass spectrometry for the quantitative detection of 17 PFAS: perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), linear perfluorooctanoic acid (n-PFOA), branched isomers of PFOA (Sb-PFOA), perfluorononanoic acid (PFNA), pefluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS), linear perfluorooctane sulfonic acid (n-PFOS), monomethyl branched isomers of PFOS (Sm-PFOS), 2,3,3,3,-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate (HFPO-DA or GenX), dodecafluoro-3H-4,8-dioxanoate (DONA), and 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (9Cl-PF3ONS). Briefly, after incubation with β-glucuronidase followed by dilution with formic acid, 50 μL of urine 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 as described in detail (Kato, et al. 2018).

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

Seventeen PFAS were measured in a one-third subsample of persons 6+ 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” (e.g., SSPFNAL) 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 (e.g., SSPFNAL=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 (e.g., SSPFNA) provides the analytic result for each analyte.

The lower limit of detection (LLOD, in ng/mL) for the seventeen PFAS are:

Variable Name

SAS Label 

LLOD 

SSCLPF

9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (ng/mL)

0.10

SSDONA

Adona (ammonium salt of 4,8-dioxa-3H-perfluorononanoate)  (ng/mL)

0.10

SSGENX

GenX (HFPO-DA or ammonium salt of 2,3,3,3,-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoateammonium salt of 2,3,3,3,-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate) (ng/mL)

0.10

SSPFBA

 Perflurobutanoic acid (ng/mL)

0.10

SSFPEA

 Perfluoropentanoic acid (ng/mL)

0.10

SSPFHA

 Perfluorohexanoic acid (ng/mL)

0.10

SSPFHP

 Perfluoroheptanoic acid (ng/mL)

0.10

SSNFOA

 Linear perfluorooctanoate (ng/mL)

0.10

SSBFOA

 Branched isomers of perfluorooctanoate (ng/mL)

0.10

SSPFNA

 Perfluorononanoic acid (ng/mL)

0.10

SSPFDE

 Pefluorodecanoic acid (ng/mL)

0.10

SSPFUA

 Perfluoroundecanoic acid (ng/mL)

0.10

SSPFBS

 Perfluorobutane sulfonic acid (ng/mL)

0.10

SSPFHS

Perfluorohexane sulfonic acid (ng/mL)

0.10

SSFHPS

Perfluoroheptane sulfonic acid (ng/mL)

0.10

SSNFOS

 Linear perfluorooctane sulfonate (PFOS) (ng/mL)

0.10

SSMFOS

 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 6 YEARS - 150 YEARS

WTSB2YR - 1/3 subsample weights

Variable Name:
WTSB2YR
SAS Label:
1/3 subsample weights
English Text:
Subsample B Weights
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
14988.396826 to 482310.7883 Range of Values 2682 2682
. Missing 0 2682

SSCLPF - 9-chlorohexadecafluoro3oxanonane (ng/mL)

Variable Name:
SSCLPF
SAS Label:
9-chlorohexadecafluoro3oxanonane (ng/mL)
English Text:
9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSCLPFL - 9-chlorohexadecafluoro(ng/mL) Comt code

Variable Name:
SSCLPFL
SAS Label:
9-chlorohexadecafluoro(ng/mL) Comt code
English Text:
9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682

SSDONA - Adona(8dioxa3Hperfluorononanoate)(ng/mL)

Variable Name:
SSDONA
SAS Label:
Adona(8dioxa3Hperfluorononanoate)(ng/mL)
English Text:
Adona (ammonium salt of 4,8-dioxa-3H-perfluorononanoate) (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSDONAL - Adona(perfluorononanoate) Comt code

Variable Name:
SSDONAL
SAS Label:
Adona(perfluorononanoate) Comt code
English Text:
Adona (ammonium salt of 4,8-dioxa-3H-perfluorononanoate) (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682

SSGENX - GenX(HFPO-DA propanoateammonium(ng/mL)

Variable Name:
SSGENX
SAS Label:
GenX(HFPO-DA propanoateammonium(ng/mL)
English Text:
GenX(HFPO-DA propanoateammonium salt of heptafluoropropoxy)-propanoate)(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.4 Range of Values 2682 2682
. Missing 0 2682

SSGENXL - GenX(HFPO-DA propanoateammonium Cmt code

Variable Name:
SSGENXL
SAS Label:
GenX(HFPO-DA propanoateammonium Cmt code
English Text:
GenX(HFPO-DA propanoateammonium salt of heptafluoropropoxy)-propanoate) Cmt code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 30 30
1 Below lower detection limit 2652 2682
. Missing 0 2682

SSPFBA - Perflurobutanoic acid (ng/mL)

Variable Name:
SSPFBA
SAS Label:
Perflurobutanoic acid (ng/mL)
English Text:
Perflurobutanoic acid (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 3.4 Range of Values 2682 2682
. Missing 0 2682

SSPFBAL - Perflurobutanoic acid (ng/mL) Comt code

Variable Name:
SSPFBAL
SAS Label:
Perflurobutanoic acid (ng/mL) Comt code
English Text:
Perflurobutanoic acid (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 297 297
1 Below lower detection limit 2385 2682
. Missing 0 2682

SSFPEA - Perfluoropentanoic acid (ng/mL)

Variable Name:
SSFPEA
SAS Label:
Perfluoropentanoic acid (ng/mL)
English Text:
Perfluoropentanoic acid (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSFPEAL - Perfluoropentanoic acid (ng/mL)Comt code

Variable Name:
SSFPEAL
SAS Label:
Perfluoropentanoic acid (ng/mL)Comt code
English Text:
Perfluoropentanoic acid (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682

SSPFHA - Perfluorohexanoic acid (ng/mL)

Variable Name:
SSPFHA
SAS Label:
Perfluorohexanoic acid (ng/mL)
English Text:
Perfluorohexanoic acid (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 7.5 Range of Values 2682 2682
. Missing 0 2682

SSPFHAL - Perfluorohexanoic acid (ng/mL) Comt code

Variable Name:
SSPFHAL
SAS Label:
Perfluorohexanoic acid (ng/mL) Comt code
English Text:
Perfluoropentanoic acid (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 636 636
1 Below lower detection limit 2046 2682
. Missing 0 2682

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.3 Range of Values 2682 2682
. Missing 0 2682

SSPFHPL - Perfluoroheptanoic acid (ng/mL)Comt code

Variable Name:
SSPFHPL
SAS Label:
Perfluoroheptanoic acid (ng/mL)Comt code
English Text:
Perfluoroheptanoic acid (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 28 28
1 Below lower detection limit 2654 2682
. Missing 0 2682

SSNFOA - Linear perfluorooctanoate (ng/mL)

Variable Name:
SSNFOA
SAS Label:
Linear perfluorooctanoate (ng/mL)
English Text:
Linear perfluorooctanoate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSNFOAL - Linear perfluorooctanoate Comt code

Variable Name:
SSNFOAL
SAS Label:
Linear perfluorooctanoate Comt code
English Text:
Linear perfluorooctanoate (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682

SSBFOA - Branch isomers-perfluorooctanoate(ng/mL)

Variable Name:
SSBFOA
SAS Label:
Branch isomers-perfluorooctanoate(ng/mL)
English Text:
Branched isomers of perfluorooctanoate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.1 Range of Values 2682 2682
. Missing 0 2682

SSBFOAL - Br. isomers-perfluorooctanoate Comt code

Variable Name:
SSBFOAL
SAS Label:
Br. isomers-perfluorooctanoate Comt code
English Text:
Branched isomers of perfluorooctanoate (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 3 3
1 Below lower detection limit 2679 2682
. Missing 0 2682

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.1 Range of Values 2682 2682
. Missing 0 2682

SSPFNAL - Perfluorononanoic acid (ng/mL) Comt code

Variable Name:
SSPFNAL
SAS Label:
Perfluorononanoic acid (ng/mL) Comt code
English Text:
Perfluorononanoic acid (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1 1
1 Below lower detection limit 2681 2682
. Missing 0 2682

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSPFDEL - Pefluorodecanoic acid (ng/mL) Comt code

Variable Name:
SSPFDEL
SAS Label:
Pefluorodecanoic acid (ng/mL) Comt code
English Text:
Pefluorodecanoic acid (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSPFUAL - Perfluoroundecanoic acid(ng/mL)Comt code

Variable Name:
SSPFUAL
SAS Label:
Perfluoroundecanoic acid(ng/mL)Comt code
English Text:
Perfluoroundecanoic acid (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSPFBSL - Perfluorobutane sulfonic acid Comt code

Variable Name:
SSPFBSL
SAS Label:
Perfluorobutane sulfonic acid Comt code
English Text:
Perfluorobutane sulfonic acid (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.1 Range of Values 2682 2682
. Missing 0 2682

SSPFHSL - Perfluorohexane sulfonic acid Comt code

Variable Name:
SSPFHSL
SAS Label:
Perfluorohexane sulfonic acid Comt code
English Text:
Perfluoroheptane sulfonic acid (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1 1
1 Below lower detection limit 2681 2682
. Missing 0 2682

SSFHPS - Perfluoroheptane sulfonic acid (ng/mL)

Variable Name:
SSFHPS
SAS Label:
Perfluoroheptane sulfonic acid (ng/mL)
English Text:
Perfluoroheptane sulfonic acid (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.1 Range of Values 2682 2682
. Missing 0 2682

SSFHPSL - Perfluoroheptane sulfonic acid Comt code

Variable Name:
SSFHPSL
SAS Label:
Perfluoroheptane sulfonic acid Comt code
English Text:
Perfluoroheptane sulfonic acid (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1 1
1 Below lower detection limit 2681 2682
. Missing 0 2682

SSNFOS - Linear perfluorooctane sulfonate(ng/mL)

Variable Name:
SSNFOS
SAS Label:
Linear perfluorooctane sulfonate(ng/mL)
English Text:
Linear perfluorooctane sulfonate (PFOS) (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.6 Range of Values 2682 2682
. Missing 0 2682

SSNFOSL - Lin perfluorooctane sulfonate Comt code

Variable Name:
SSNFOSL
SAS Label:
Lin perfluorooctane sulfonate Comt code
English Text:
Linear perfluorooctane sulfonate (PFOS) (ng/mL) Comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1 1
1 Below lower detection limit 2681 2682
. Missing 0 2682

SSMFOS - Monomethyl branch isomers-PFOS (ng/mL)

Variable Name:
SSMFOS
SAS Label:
Monomethyl branch isomers-PFOS (ng/mL)
English Text:
Monomethyl branched isomers of PFOS (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.07 Range of Values 2682 2682
. Missing 0 2682

SSMFOSL - Monomethyl branched isomers-PFOS Cmt cd

Variable Name:
SSMFOSL
SAS Label:
Monomethyl branched isomers-PFOS Cmt cd
English Text:
Monomethyl branched isomers of PFOS (ng/mL) Comment code
Target:
Both males and females 6 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 2682 2682
. Missing 0 2682