• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • WTSSPH2Y - SSPFAC_H 2 year weights
  • SSPFSA - Perfluorooctane sulfonamide (ng/mL)
  • SSPFSAL - Perfluorooctane sulfonam Cmt code
  • SSMPAH - 2(N-methyl-perfluor sulfon) acid (ng/mL)
  • SSMPAHL - 2(N-methyl-perfluor sulfon) acid Cmt cd
  • SSEPAH - 2(N-ethyl-perfluor sulfon) acid (ng/mL)
  • SSEPAHL - 2(N-ethyl-perfluor sulfon) acid Cmt cd
  • SSPFDE - Pefluorodecanoic acid (ng/mL)
  • SSPFDEL - Pefluorodecanoic acid Cmt code
  • SSPFBS - Perfluorobutane sulfonic acid (ng/mL)
  • SSPFBSL - Perfluorobutane sulfonic acid Cmt code
  • SSPFHP - Perfluoroheptanoic acid (ng/mL)
  • SSPFHPL - Perfluoroheptanoic acid Cmt code
  • SSPFNA - Perfluorononanoic acid (ng/mL)
  • SSPFNAL - Perfluorononanoic acid Cmt code
  • SSPFUA - Perfluoroundecanoic acid (ng/mL)
  • SSPFUAL - Perfluoroundecanoic acid Cmt cd
  • SSPFDO - Perflurododecanoic acid (ng/mL)
  • SSPFDOL - Perflurododecanoic acid Cmt code
  • SSPFHS - Perfluorohexane sulfonic acid (ng/mL)
  • SSPFHSL - Perfluorohexane sulfonic acid Cmt code
  • SSNPFOA - Linear perfluorooctanoate (ng/mL)
  • SSNPFOAL - Linear perfluorooctanoate Cmt Code
  • SSBPFOA - Branch isomers-perfluorooctanoate(ng/mL)
  • SSBPFOAL - Branch isomers-perfluorooctanoate Cmt cd
  • SSNPFOS - Linear perfluorooctane sulfonate (ng/mL)
  • SSNPFOSL - Linear perfluorooctane sulfonate cmt cd
  • SSMPFOS - Monomethyl br. isomers of PFOS (ng/mL)
  • SSMPFOSL - Monomethyl br. isomers of PFOS cmt cd

National Health and Nutrition Examination Survey

2013-2014 Data Documentation, Codebook, and Frequencies

Perfluoroalkyl and Polyfluoroalkyl Substances in US children 3-11 Years of Age (SSPFAC_H)

Data File: SSPFAC_H.xpt

First Published: August 2017

Last Revised: April 2022

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.

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

Subsample Weights

Sample weights are required to analyze these data properly. Specific sample weights for this subsample are included in this data file and should be used when analyzing these data. Previous versions of this data file included a sample weight variable (WTSS2YR) but when observations were removed from this data file, a new sample weight was created, and a new sample weight variable was added to this data file (WTSSPH2Y). 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

• Caudill SP, Schleicher RL, Pirkle JL. Multi-rule quality control for the age-related eye disease study. Statist Med 2008;27:4094-4106.
• CDC. 2015. Fourth National Report on Human Exposure to Environmental Chemicals, Updated Tables, February 2015. In http://www.cdc.gov/biomonitoring/pdf/FourthReport_UpdatedTables_Feb2015.pdf. Atlanta, GA:Centers for Disease Control and Prevention; National Center for Environmental Health; Division of Laboratory Sciences.
• Kato K, Basden BJ, Needham LL, Calafat AM. 2011. Improved selectivity for the analysis of maternal serum and cord serum for polyfluoroalkyl chemicals. J Chromatogr A: 2133-2137.
• Kato K, Calafat AM, Wong LY, Wanigatunga AA, Caudill SP, Needham LL. 2009. Polyfluoroalkyl Compounds in Pooled Sera from Children Participating in the National Health and Nutrition Examination Survey 2001-2002. Environ Sci Technol 43: 2641-2647.

Codebook and Frequencies