05:55am Wednesday 20 September 2017

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CINCINNATI—Children in Cincinnati whose mothers were exposed to relatively high levels of the chemical PFOA during pregnancy experienced more rapid body fat gain and higher body fat by age 8 than children whose mothers were less exposed, according to a new analysis in the journal Obesity.


The research team was led by Joseph Braun, PhD, assistant professor of epidemiology at Brown University, which issued a news release describing the findings. Co-authors included two faculty members in the University of Cincinnati (UC) College of Medicine: Aimin Chen, MD, PhD, Department of Environmental Health, and Kimberly Yolton, PhD, Department of Pediatrics.

The Yolton Lab at Cincinnati Children’s Hospital Medical Center is home to the Health Outcomes and Measures of the Environment (HOME) Study involving a collaborative group of investigators from Cincinnati Children’s and other institutions who seek to quantify the impact of low-level prenatal and childhood exposures to environmental chemicals on health, growth and neurobehavioral outcomes. The HOME study has followed its mother and child participants from approximately 16 weeks gestation to child 8 years of age. Although the study is no longer recruiting new participants, it continues to follow those who were previously enrolled.

PFOA—perfluorooctanoic acid—is a suspected “obesogen,” because lab studies suggest exposure to its broader family of PFAS chemicals may alter the body’s metabolism and fat cell development.

This study of 204 Cincinnati mothers and their children looked at potential childhood effects of PFOA, an industrial chemical used in the manufacture oil/water repellant textiles, firefighting foam, and nonstick coatings. The substance was used for decades at a chemical plant upstream of the city along the Ohio River in West Virginia.

The new analysis derives from the HOME study (Health Outcomes and Measures of the Environment), a cohort of 389 mothers and their children in Cincinnati who have been followed since pregnancy. The HOME study found that the average exposure measured among the mothers in the cohort was more than twice that of a representative sample of pregnant women from the United States.

The researchers found that relatively high exposure had a statistically significant association with the amount and pace of body fat gain in children during the first eight years of life. The mothers and children in the new analysis were classified into three subgroups, or terciles, based on the mother’s exposure level during pregnancy.

“The increase in body fat we observed among children born to women in the second and third PFOA terciles was equivalent to a 0.4 to 1.1 kilogram (0.9 to 2.4 pounds) increase in body fat for a child of average weight in the cohort at 8 years of age,” the scientists wrote.

While the extra adipose correlated with PFOA exposure may seem subtle, Braun said, it’s still enough to be a significant public health concern. Excess body fat may increase the risk of Type 2 diabetes later in life.

“There isn’t a threshold at which we say you shouldn’t add more fat mass—any more fat mass is bad fat mass,” Braun said. “When you look at the risk of diabetes in adults, the risk is pretty much linear across the whole range of BMI.”

Adds Chen: “This study finding highlights the need to further examine the role of persistent organic chemicals on long-term adiposity change during childhood. It particularly points to the importance to understand that fetal exposure during pregnancy could have lasting effects because the fetal period may set metabolic responses for future obesity development.

“There is also a need to examine postnatal exposures in addition to in utero exposure to generate comprehensive understanding of the windows of vulnerability in adiposity. Dr. Braun will lead that investigation direction.”

Given its observational nature, the study only shows an association between prenatal PFOA levels and childhood adiposity. It does not prove that the exposure caused the effect. More research is required, Braun said.

Overall studies of PFOA and weight gain have been mixed, the researchers acknowledged. In this study, children were not only weighed and measured to calculate BMI, but also their quantity of fat tissue, or adiposity, was measured. Braun said this makes the study data possibly more reliable than a larger prior study, done closer to the West Virginia plant, that relied on self-reports of weight. That study found no effect.

Also the new study is rare in that reports the BMI gain of children over a long period of time. The researchers found that children born to women with higher levels of PFOA in their blood during pregnancy gain BMI more rapidly between 2 and 8 years of age. Children in the highest PFOA tercile had the lowest BMI at age 2, but by age 8 they had a BMI similar to the children in the first tercile.

The finding that children of more highly exposed mothers start smaller and then gain weight faster could explain why studies that look at only one moment in time might find an association with PFOA and higher fat, while another study that looked at an earlier time might find the opposite.

In the analysis, Braun and his colleagues statistically controlled for a wide variety of potentially confounding factors, including the mothers’ education, income, race, BMI, diet, smoking, and exposure to other potential obesogens like bisphenol A and phthalates. But the study did not account for the diets of the children or for water intake of either mothers or children. Water intake is one of the presumed means of PFOA exposure and is something Braun hopes to measure in the future.

The Greater Cincinnati Water Works, which uses Ohio River water and groundwater from the Great Miami Aquifer as sources, says chemical levels in its treated water exceed federal safety standards. It uses granular activated carbon (GAC) for filtration, which it says has been recognized as the best available technology for removing the most common chemicals found in spills in the Ohio River including PFOAs. 

The study raises concerns about potential effects of PFOA exposure that should be pursued further, Braun said.

“I think it’s significant enough to warrant additional investigation to see if the trends continue as these children get older,” Braun said, “and to see if other markers of either fetal growth or rapid early infancy growth are associated with these exposures.”

The National Institute of Environmental Health Sciences supported the research (grants: R01ES020346, PO1ES11261, R01ES014575, R01ES020349). Megan Romano, PhD, of Brown and Glenys Webster, PhD, and Bruce Lanphear, MD, of Simon Fraser University were co-authors in addition to Braun, Chen and Yolton.

NOTE: This story was adapted from a news release issued by Brown University.

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