National Health and Nutrition Examination Survey

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).

Study participants aged 3-11 years from of NHANES 2001 - 2002 with stored serum available to prepare pooled samples.

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)).

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.

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.