Academic journal article Environmental Health Perspectives

Polyfluoroalkyl Chemicals and Menopause among Women 20-65 Years of Age (NHANES)

Academic journal article Environmental Health Perspectives

Polyfluoroalkyl Chemicals and Menopause among Women 20-65 Years of Age (NHANES)

Article excerpt

Introduction

Polyfluoroalkyl chemicals (PFCs) are manmade compounds that have been used in a number of common consumer and industrial products such as food containers; stain-and water-resistant protection for clothing, furniture, and carpets; paints; fire-fighting foam; and photographic emulsifiers (Lau et al. 2007). PFCs are ubiquitously present and persistent in the environment (Lau et al. 2007), and although there are demographic, geographic, and temporal differences, exposures in the general population are widespread. Four PFC analytes--perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), and perfluorohexane sulfonate (PFHxS)--are commonly detected in humans (Calafat et al. 2006; Fromme 2007; Kato et al. 2011). Unlike traditional persistent organic pollutants, which are lipophilic and stored primarily in fat tissue, PFOS and PFOA are both lipophobic and hydrophobic. After absorption, they persist in the body by forming chemical bonds to proteins in serum, rather than accumulating in lipids (Jones et al. 2003; Organisation for Economic Co-operation and Development 2002). Serum levels of PFCs reflect long-term exposures to these contaminants [U.S. Environmental Protection Agency (EPA) 2012b], with estimated geometric mean half-lives of 7.3 years (95% CI: 5.8, 9.2) for PFHxS, 4.8 years (95% CI: 4.0, 5.8) for PFOS, and 3.5 years (95% CI: 3.0, 4.1) for PFOA (Olsen et al. 2007). However, in a more recent study, Bartell et al. (2010) estimated a shorter median half-life for serum PFOA (2.3 years; 95% CI: 2.1, 2.4).

PFCs are potential endocrine disruptors, and effects of PFOS and PFOA on endocrine function have been reported in animal studies (Jensen and Leffers 2008; Zhao et al. 2010). Less is known about associations between PFCs and human endocrine function. Melzer et al. (2010) reported that higher concentrations of serum PFOA and PFOS were associated with current thyroid disease based on NHANES (National Health and Nutrition Examination Survey) data from 1999-2000, 2003-2004, and 2005-2006. In addition, in a population-based cohort of adolescents and young adults in Taiwan, Lin et al. (2013) observed a positive association between serum levels of PFNA and serum levels of thyroxine ([T.sub.4]) Yet, other studies have reported no association between PFOS or PFOA levels and thyroid function. These include occupational studies with high levels of exposure (Olsen et al. 2003; Olsen and Zobel 2007); a study of residents of a water district in southeastern Ohio, where there is significant environmental exposure to PFOA (Emmett 2006); studies of populations in Korea (Ji et al. 2012) and China (Lin et al. 2013); a study of Inuit adults (Dallaire et al. 2009); and studies of pregnant women (Chan et al. 2011; Inoue et al. 2004). In the United States, one of the largest efforts to investigate the impact of exposures to PFCs was initiated by the C8 Science Panel, which was created as part of a settlement agreement stemming from PFOA (or C8) contamination of drinking water in six water districts in two states near the DuPont Washington Works facility near Parkersburg, West Virginia (Frisbee et al. 2009). In this exposed population, high environmental levels of PFOA in water were associated with delayed onset of puberty in girls (Lopez-Espinosa et al. 2011) as well as earlier menopause (Knox et al. 2011). Knox et al. (2011) found that serum PFOS and PFOA were significantly higher (p < 0.0001) in women 40-55 years of age who had a hysterectomy compared with women who had not. However, because the authors did not observe the timing of PFC exposure relative to menopause, causal inference is limited. One noncausal explanation for an association between PFCs and natural menopause is that elimination of PFCs via the loss of menstrual blood and tissue might result in lower serum levels in menstruating women than in postmenopausal women (Knox et al. 2011).

We investigated associations between multiple PFCs (PFOS, PFOA, PFNA, and PFHxS) and age at natural and surgically induced (hysterectomy) menopause using NHANES data. …

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