Table of Contents

Component Description

Human exposure to per- and polyfluoroalkyl substances (PFAS) is a growing public health concern. PFAS encompass thousands of environmentally persistent man-made chemicals that have been used in industry and consumer products worldwide since the 1950s. These chemicals can be used in food packaging and many other household products, as well as aqueous firefighting foams (AFFF).  PFAS have been detected in air, soil, and water.

Exposure to a select number of PFAS in the United States is widespread as suggested by nearly universal detection of these chemicals in serum collected from NHANES participants (CDC, 2019). Changes in the manufacture of several of the PFAS included in NHANES since the early 2000s may result in a potential increased market use of other PFAS. Yet, the extent of exposure to these newer and alternative PFAS among the general U.S. population is rather limited and only based on the use of urine as a matrix (Calafat et al. 2019). To fill in this data gap, NCEH modified and validated an analytical method used at CDC for quantifying five additional PFAS in serum.

These additional PFAS are: dodecafluoro-3H-4,8-dioxanoate (DONA), tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate (GENX), 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (CLPF), perfluoro-1-heptanesulfonate (FHPS), and perfluorohexanoate (PFHA).

Eligible Sample

One-third subsample of participants aged 12+ years from NHANES 2017-2018 with stored serum (N=1,929).

Description of Laboratory Methodology

The method uses 50 µL serum and is based on a modification of an existing method developed to quantify PFAS in serum and urine (Kato et al. 2018).  Concentrations of PFAS are quantified by on online solid phase extraction (SPE) coupled to high performance liquid chromatography-isotope dilution tandem mass spectrometry (HPLC-MS/MS) using validated analytical approaches published in the peer-reviewed literature.  The limits of detection are in the sub-parts-per-billion (ng/mL) range. 

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 reagent 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

Detection Limits

The 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., SSDONAL) 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 analytic results below the limit of detection (ex., SSDONAL=1), an imputed fill value was placed in the analyte results field. This value is the limit of detection divided by square root of 2 (LOD/√2). The other variable prefixed SS (ex., SSDONA) provides the analytic result for that analyte.

The limits of detection (LODs, in ng/mL) for DONA, GENX, CLPF, FHPS, and PFHA are 0.1.

Variable Name

Analyte name

LOD

(ng/mL)

SSDONA

Dodecafluoro-3H-4,8-dioxanoate

0.1

SSGENX

Tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate

0.1

SSCLPF

9-Chlorohexadecafluoro-3-oxanonane-1-sulfonate

0.1

SSFHPS

Perfluoro-1-heptanesulfonate

0.1

SSPFHA

Perfluorohexanoate

0.1

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 12 YEARS - 150 YEARS

SSDONA - Dodecafluoro-3H-4,8-dioxanoate

Variable Name:
SSDONA
SAS Label:
Dodecafluoro-3H-4,8-dioxanoate
English Text:
Dodecafluoro-3H-4,8-dioxanoate
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.071 to 0.071 Range of Values 1929 1929
. Missing 0 1929

SSDONAL - Dodecafluoro-3H-4,8-dioxanoate cmt cd

Variable Name:
SSDONAL
SAS Label:
Dodecafluoro-3H-4,8-dioxanoate cmt cd
English Text:
Dodecafluoro-3H-4,8-dioxanoate 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 1929 1929
. Missing 0 1929

SSGENX - GenX

Variable Name:
SSGENX
SAS Label:
GenX
English Text:
GenX
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.071 to 0.1 Range of Values 1929 1929
. Missing 0 1929

SSGENXL - GenX cmt cd

Variable Name:
SSGENXL
SAS Label:
GenX cmt cd
English Text:
GenX 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 1 1
1 Below lower detection limit 1928 1929
. Missing 0 1929

SSCLPF - Chlorohexadecafluorooxanonane sulfonate

Variable Name:
SSCLPF
SAS Label:
Chlorohexadecafluorooxanonane sulfonate
English Text:
Chlorohexadecafluorooxanonane sulfonate
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.071 to 11.5 Range of Values 1929 1929
. Missing 0 1929

SSCLPFL - Chlorohexadecafluorooxanonane sulfon cd

Variable Name:
SSCLPFL
SAS Label:
Chlorohexadecafluorooxanonane sulfon cd
English Text:
Chlorohexadecafluorooxanonane sulfonate 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 1688 1929
. Missing 0 1929

SSFHPS - Perfluoro-1-heptanesulfonate

Variable Name:
SSFHPS
SAS Label:
Perfluoro-1-heptanesulfonate
English Text:
Perfluoro-1-heptanesulfonate
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.071 to 13.2 Range of Values 1929 1929
. Missing 0 1929

SSFHPSL - Perfluoro-1-heptanesulfonate cmt cd

Variable Name:
SSFHPSL
SAS Label:
Perfluoro-1-heptanesulfonate cmt cd
English Text:
Perfluoro-1-heptanesulfonate 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 1483 1483
1 Below lower detection limit 446 1929
. Missing 0 1929

SSPFHA - Perfluorohexanoate

Variable Name:
SSPFHA
SAS Label:
Perfluorohexanoate
English Text:
Perfluorohexanoate
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.071 to 0.9 Range of Values 1929 1929
. Missing 0 1929

SSPFHAL - Perfluorohexanoate cmt cd

Variable Name:
SSPFHAL
SAS Label:
Perfluorohexanoate cmt cd
English Text:
Perfluorohexanoate 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 9 9
1 Below lower detection limit 1920 1929
. Missing 0 1929

WTSB2YR - 1/3 subsample weights

Variable Name:
WTSB2YR
SAS Label:
1/3 subsample weights
English Text:
1/3 subsample weights
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
14832.673125 to 1395405.4654 Range of Values 1929 1929
. Missing 0 1929