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Introduction
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are widespread and persistent environmental contaminants detected in many populations worldwide, including among pregnant women and infants (Cariou et al. 2015; Jiang et al. 2014; Kato et al. 2014; Manzano-Salgado et al. 2015; Okada et al. 2013). PFAS have been used for decades in industrial and commercial applications, including surface treatments for fabrics, food packaging, and aqueous film-forming foams for extinguishing fires (Buck et al. 2011; Prevedouros et al. 2006). The serum concentrations of certain PFAS have declined in the United States over the past decade (CDC 2015) following the phase out of perfluorooctane sulfonate (PFOS) production by 3M in 2000–2002 (U.S. EPA 2000) and the listing of PFOS in Annex B of the Stockholm Convention on Persistent Organic Pollutants in 2009 (Secretariat of the Stockholm Convention 2010). However, other PFAS concentrations have remained relatively constant over the same time period (CDC 2015), suggesting that human exposure is ongoing.
The ubiquitous presence of certain PFAS in humans is of concern because animal studies have demonstrated hepatotoxicity, immunotoxicity, and developmental toxicity resulting from high dose exposure (Lau et al. 2007). Epidemiologic studies in a population highly exposed to one PFAS, perfluorooctanoate (PFOA), have shown associations between PFAS exposure and chronic diseases, including kidney and testicular cancers (Barry et al. 2013), ulcerative colitis (Steenland et al. 2013), high cholesterol (Steenland et al. 2009), and pregnancy-induced hypertension (Darrow et al. 2013). Strong correlations between maternal and cord blood PFAS concentrations suggest transfer to the fetus from maternal circulation (Aylward et al. 2014). Maternal concentrations of PFOA during pregnancy have been previously associated with lower offspring birth weight in systematic reviews of the human evidence (Bach et al. 2015a; Johnson et al. 2014), as well an integrative assessment of human and nonhuman animal evidence (Lam et al. 2014), but the factors responsible for this association, if causal, have not been established. Moreover, some recent studies have reported positive associations between maternal PFAS concentrations during pregnancy and offspring body weight, waist circumference, and other indicators of adiposity in childhood and early adulthood (Braun et al. 2016; Halldorsson et al. 2012; Høyer et al. 2015; Mora et al. 2017), while another study reported null associations (Andersen et al. 2013).
Fetal growth depends on the transfer...