Computational estimates of daily aggregate exposure to PFOA/PFOS from 2011 to 2017 using a basic intake model

Abstract

Background: Human exposure to per- and polyfluoroalkyl substances has been modeled to estimate serum concentrations. Given that the production and use of these compounds have decreased in recent years, especially PFOA and PFOS, and that additional concentration data have become available from the US and other industrialized countries over the past decade, aggregate median intakes of these two compounds were estimated using more recent data.

Methods: Summary statistics from secondary sources were collected, averaged, and mapped for indoor and outdoor air, water, dust, and soil for PFOA and PFOS to estimate exposures for adults and children. European dietary intake estimates were used to estimate daily intake from food.

Results: In accordance with decreased concentrations in media, daily intake estimates among adults, i.e., 40 ng/day PFOA and 40 ng/day PFOS, are substantially lower than those reported previously, as are children's estimates of 14 ng/day PFOA and 17 ng/day PFOS. Using a first-order pharmacokinetic model, these results compare favorably to the National Health and Nutrition Examination Survey serum concentration measurements.

Conclusion: Concomitant blood concentrations support this enhanced estimation approach that captures the decline of PFOA/PFOS serum concentration over a decade.

Keywords: Aggregate daily; Exposure model; PFOA; PFOS.

Fig. 1. Generalized demonstrated approach to assessing exposure in this paper.

GM geometric mean, GSD geometric standard deviation, NHANES National Health and Nutrition Examination Survey, PK pharmacokinetic.

Fig. 2. PFOA and PFOS exposure route boxplots for adults and children.

Daily route-specific estimates are provided for dust ingestion, dietary ingestion, water ingestion, dermal dust absorption, indoor inhalation, outdoor inhalation, and soil ingestion in ng/day. Boxplots show estimated for PFOA, adults and children, followed by PFOS, adults and children. n = 2000.

Fig. 3. The 2013-2014 NHANES serum concentration and model estimate for PFOA and PFOS in adults.

The distribution represents measured serum concentrations (ng/mL) in NHANES. The red and blue lines show the medians for the NHANES distribution and the model estimate respectively. Plots for PFOA and PFOS are shown for adults (age >= 18). NHANES data n = 1988.

Fig. 4. A sensitivity analysis of steady-state and dynamical models for PFOA and PFOS in Adults with variation in volume of distribution (Vd), and the corresponding impact on the serum concentration (ng/mL).

The red, blue, and black lines represent different Vd values. The steady-state model returns a horizontal line, whereas the dynamical model is the curved line that approaches steady-state over time. The first plot is PFOA in adults and the second is PFOS in adults.