Emory University Research on Per- and Polyfluoroalkyl Substances (PFASs)
Per- and polyfluoroalkyl substances (PFASs), also known as PFCs, represent a highly ubiquitous group of synthetic chemicals used in products ranging from water and oil repellents and lubricants to firefighting foam. Emory University's Rollins School of Public Health has conducted research on the effects of these persistent pollutants, commonly used as surfactants, on human health. These substances can enter and accumulate in multiple tissue matrices in up to 100% of people assessed. PFCs are used in the production of fluoropolymers and are found widely in protective coatings of packaging products, clothes, furniture, and non-stick cookware. They are persistent compounds found abundantly in the environment and human exposure is common. PFCs have been detected in human sera, breast milk, and cord blood.
Impact on Infant Growth
A study from Emory University's Rollins School of Public Health, published online in Environmental Health Perspectives, investigated the impact of prenatal exposure to PFCs on infant growth. The study, funded by the Centers for Disease Control and Prevention, included 447 British girls and their mothers in the United Kingdom participating in the Avon Longitudinal Study of Parents and Children, a large-scale health research project that has provided a vast amount of genetic and environmental information since it began in the early 1990s. Pregnant women who are highly exposed to common environmental chemicals - polyfluoroalkyl compounds (PFCs) - have babies that are smaller at birth and larger at 20 months of age.
The researchers measured maternal serum concentrations of PFOS, PFOA and PFHxS during pregnancy and obtained data on the weight and length of the girls at birth, 2, 9 and 20 months. They explored associations between prenatal PFC concentrations and weight at birth as well as changes in weight-for-age scores between birth and 20 months. The researchers found that even though girls with higher exposure were smaller than average (43rd percentile) at birth, they were heavier than average (58th percentile) by 20 months of age. The authors say this path may lead to obesity at older ages.
According to Marcus, a recent study in Denmark found that women exposed to PFCs in the womb were more likely to be overweight at age 20. And experimental studies with mice have shown that exposure in the womb led to higher levels of insulin and heavier body weight in adulthood.
Marcus and her colleagues focused on the three most studied PFCs: perfluorooctane sulfonate (PFS), perfluorooctanoate (PFOA) and perfluorohexane sulfonate (PFHxS).
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"Previous animal and human research suggests prenatal exposures to PFCs may have harmful effects on fetal and postnatal growth," says lead researcher Michele Marcus, a professor of epidemiology in Emory's Rollins School of Public Health and the assistant program director at Kaiser Permanente's Center for Health Research. "Our findings are consistent with these studies and emerging evidence that chemicals in our environment are contributing to obesity and diabetes and demonstrate that this trajectory is set very early in life for those exposed."
Research on Spermatogenesis
While animal models strongly identify these compounds as male reproductive toxicants, with exposed rodents experiencing declines in sperm count, alterations in hormones, and DNA damage in spermatids, among other adverse outcomes, human studies report conflicting conclusions as to the reproductive toxicity of these chemicals.
Using an innovative, human stem-cell-based model of spermatogenesis, researchers assessed the effects of the PFASs perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and a mixture of PFOS, PFOA, and PFNA for their impacts on human spermatogenesis in vitro under conditions relevant to the general and occupationally exposed populations. Here, they show that PFOS, PFOA, PFNA, and a mixture of PFOS, PFOA, and PFNA do not decrease in vitro germ cell viability, consistent with reports from human studies. These compounds do not affect mitochondrial membrane potential or increase reactive oxygen species generation, and they do not decrease cell viability of spermatogonia, primary spermatocytes, secondary spermatocytes, or spermatids in vitro under the conditions examined. However, exposure to PFOS, PFOA, and PFNA reduces expression of markers for spermatogonia and primary spermatocytes.
Broader Research Context
Research has also explored the levels of PFCs in different populations and their potential health effects. For example, studies have examined PFC concentrations in cohorts and with pregnant women in NHANES (2005-2006). Some research indicates that PFC levels were higher in women from AK MOMS compared to NHANES. Other studies have shown that PFC levels decreased from 1999-2000 to 2010-2012, except for PFHxS, which increased.
Associations between PFC exposure and various health outcomes have also been investigated, including links to lipid metabolism and spermatogenesis. The relationship between PFCs and cholesterol has been explored, as well as bioaccumulation patterns and dietary exposure. Specific compounds, such as PFDeA and PFHxS, have been examined in relation to fertility.
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