Temporal and Demographic Patterns of PFAS Exposure and the Relationship with Seafood Consumption in the U.S. General Population Using 1999-2012 NHANES Data

&ERA

United States
Environmental Protection
Agency

Temporal and Demographic Patterns of PFAS Exposure and the Relationship
with Seafood Consumption in the U.S. General Population Using 1999-2012 NHANES Data

Rebecca Jeffries Birch3, John Rogers3, Joyce Morrissey Donohueb, Lisa Larimerb and John Wathenb

Background

Perfluorooctane sulfonic acid (PFOS),
perfluorooctanoic acid (PFOA), and
perfluorononanoic acid (PFNA) are
persistent bioaccumulating perfluoroalkyl
and polyfluoroalkyl substances (PFAS)
that do not naturally occur in the
environment (ATSDR, 2018; U.S. EPA, 2016a;
U.S. EPA, 2016b). In the United States,
the manufacture of PFOS and PFOA has
been phased out, and the production of
PFNA has been reduced, but production
of all three continues overseas. These
substances persist in blood serum for
long periods of time and have been
associated with negative human health
outcomes including increased cholesterol
and uric acid levels, liver damage, immune
system effects, and cancer. PFAS have
been shown to accumulate in fish tissue
(EFSA, 2008). Several studies (Stahl et
al., 2014, U.S. EPA 2020, U.S. EPA 2021)
have found PFAS in U.S. rivers and Great
Lakes. Stahl et al. (2014) reported 90th
percentile PFOS concentrations in U.S.
rivers and Great Lakes of 38.9 ng/g (38.9
parts per billion [ppb]), 90th percentile
PFOA concentrations of 0.16 ng/g, and
90th percentile PFNA concentrations of
1.60 ng/g.

Study Purpose

This study investigates the role that
seafood (fish and shellfish from marine,
estuarine and fresh waters) consumption
plays in PFAS concentrations in human
blood serum and how PFAS exposure has
changed over time, using NHANES data in
humans 12 years and older in the U.S. for
1999-2000 and 2003-2012. Investigators
also evaluated the relationships between
PFAS serum concentrations and each of the
following: seafood consumption, year of
data collection, and demographic factors.

Author Affiliation

a West at

1600 Research Blvd
Rockville, Maryland, 20850 USA
b Off ice of Science and Technology, Office of Water,
U.S. Environmental Protection Agency,
1200 Pennsylvania Avenue, N.W.

Washington, DC, 20460 USA

Data and Methods

The Centers for Disease Control and Prevention's (CDC) National Health and
Nutrition Examination Survey (NHANES) interview and examination data
were used for this study. NHANES interview data includes demographic,
socioeconomic, dietary, and health-related questions. The examination
component includes medical, dental, and physiological measurements and
laboratory tests of blood and urine. Six two-year cycles of NHANES data,
1999-2000 and 2003-2012, were analyzed using NHANES Analytical Guidelines
(CDC 2013; CDC 2018). NHANES data from a total of 9,776 participants with
laboratory PFAS measurements, seafood frequency, consumption, and
demographic data were analyzed for this study. All analyses were weighted
using PFAS subsample weights. Serum data for PFOA, PFOS and PFNA were
analyzed in a subsample of NHANES participants that were 12 years and older.
Demographic variables—age, gender, race/ethnicity, education, and household
annual income—were included in the analysis. Dietary data from two 24-
hour recalls for each participant were used, and the estimate of the amount
of raw seafood consumed was based on the US Department of Agriculture
Food and Nutrient Database for Dietary Studies (FNDDS). Frequency of
seafood consumption was based on the number of times participants reported
consuming seafood in the past 30 days.

Transformed usual seafood intake (TUI), which represents the long-term
average intake of raw finfish and shellfish from marine, estuarine, and
fresh waters, was calculated for each participant using the EPA Method.1
Survival analysis was used to predict log-transformed PFAS concentrations
as a function of usual seafood intake and demographic covariates. Survival
analysis is a form of linear regression analysis that is useful when predicting
concentration measurements where some measurements are less than the
detection limit. In this application, survival analysis required assuming the
concentrations have an approximate log normal distribution, like those that
would have been obtained with a more sensitive technique. The detected
concentrations were reasonably consistent with this assumption.

Using the sample weights, predictors were selected for inclusion in the models
of PFOS, PFOA, and PFNA in two steps. Main effects were included if they
were significant at p < 0.05 using the SAS SURVEYREG procedure. Stepwise
selection was used to select interactions of the selected main effects. The
stepwise selection used the SAS GLMSELECT procedure to predict the log-
transformed PFAS concentrations (with substitute values for the non-detects)
using the default selection criteria. Effects that were significant predictors of
any of the three serum PFAS concentrations of interest were included in the
final models predicting serum PFOS, PFOA, and PFNA concentrations.

The final set of main effect variables were age, sex, race/ethnicity, annual
income, education, log-transformed serum cotinine, usual seafood intake,
and a linear trend over time. The final set of two-way interactions were the
interactions of time with sex, age, education, income, and TUI; the
interactions of sex with log-transformed serum cotinine, age, and race/
ethnicity; and the interaction of race/ethnicity with transformed usual
seafood intake. All predictors (except for TUI and interactions with TUI) were
used as covariates in the models predicting the probability and amount of
seafood intake using the EPA method.

Results

1 Blood serum PFOA and PFOS concentrations
decreased, and serum PFNA increased between
1999 and 2012 (Rgures 1-3).

1 Seafood consumption was positively
associated with serum PFOS, PFOA, and PFNA
concentrations. Statistical significance was
achieved for PFOS and PFNA but not for PFOA.

1 Levels of PFOS, PFOA, and PFNA were
consistently higher in males, increased with
increasing income, and vary by age and race/
ethnicity, although not with a consistent
pattern.

Sorua pfOS (ntfml)

jBi

Figure 1. Concentration of Serum PFOS from 1999-2012
S*tum PFOA

Figure 2. Concentration of Serum PFOA from 1999-2012
Scram PFNA .

1 Figure 7 shows the relative serum PFAS concentrations for the different demographic
groups represented by multiplicative differences from the overall PFAS concentration.

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Figure 7. Relative serum PFOS, PFOA, and PFNA

by demographic group, with 95% confidence intervals

For more information contact Lisa Larimer at Larimer.Lisa@epa.gov

Conclusion

1 Seafood consumption is an important exposure
route for PFOS and PFNA but less important for
PFOA.

1 Figure 8 shows that serum concentrations of
PFOS, PFOA, and PFNA changed over the study
period.

1 Declines in serum PFOA and PFOS over the
study period are consistent with the end
of manufacturing of these chemicals in the
United States. The observed increase in PFNA
suggests the possibility of the formation
of PFAS compounds by some mechanism of
transformation.

1 While the data show exposure to PFOS and PFOA
is decreasing nationally, this observed trend may
not hold particularly where people consume
more seafood or catch and eat seafood from
areas with significant contamination.

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The views expressed in this poster are those of the authors and do not necessarily
represent the views or policies of the U.S. Environmental Protection Agency.

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