Thousands of chemicals make up the PFAS (perfluoroalkyl substances) group and, thanks to their water- and grease-resistant properties, PFAS are used in everything from frying pans and food packaging to clothes, cleaning agents and firefighting foams.
However, they have long been considered harmful to health and to the environment.
The website for the United States’ Environmental Protection Agency (EPA) points out that the best known — perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) — can cause reproductive and developmental, liver and kidney, and immunological effects in laboratory animals. It adds that the most consistent findings are increased cholesterol levels among exposed populations, with more limited findings related to low infant birth weights, effects on the immune system, cancer (for PFOA), and thyroid hormone disruption (for PFOS).
Most PFAS manufacturing has been phased out in the U.S. under a number of EPA regulatory regimes, including its PFOA Stewardship Program. The European Union banned PFOS in 2008, and in January 2019 the European Food Safety Authority sharpened its appraisal of PFOS and PFOA, lowering the tolerable daily intake a thousand-fold.
Now, a new study by researchers at the Karolinska Institute, Solna, Sweden, shows how PFAS passes through the placenta throughout pregnancy to accumulate in fetal tissue.
The researchers focused on six PFAS substances, including PFOS and PFOA, and found that all appear to the same extent in fetal tissue as in the placenta. “So, when the baby is born, it already has a build-up of these chemicals in the lungs, liver, brain, and elsewhere in the body,” explains Richelle Duque Björvang, doctoral student at the department of clinical science, intervention and technology.
PFAS levels were highest in the lung and liver tissue, in some cases as high as in adults, and lowest in the brain.
“This shows how important it is for more research to be done on the health effects of different chemicals, especially in the longer term,” says Pauliina Damdimopoulou, senior researcher in the same department. “Today’s threshold values are based on an adult population rather than fetuses, which are much more susceptible.”
The accumulation of PFAS substances also was higher in male fetuses than female, prompting Damdimopoulou to note that understanding this will be an important area of further research.
“The main source of PFAS substances today is food, in the form of fish, milk, meat and eggs, or in the drinking water, if you happen to live in a polluted area. We ingest them as a cocktail of substances that can also interact with each other. It would be in line with the precautionary principle in the restriction of chemical substances to make sure that all PFAS substances disappear from our society,” she adds.
In their conclusion, the authors note that the values they present may allow extrapolation for fetal exposure of other similar compounds through computer modeling.
Meanwhile, an earlier study found that PFAS compounds also may have a role in weight gain and obesity development.
Published last year in PLOS Medicine, the “Perfluoroalkyl substances and changes in body weight and resting metabolic rate in response to weight-loss diets” study followed the two-year, diet-induced weight-loss trial (the POUNDS Lost trial) carried out in Boston, Mass., and Baton Rouge, La.
Here, the researchers measured plasma concentrations of PFAS at baseline in 621 overweight and obese men and women and collected information on changes in body weight, resting metabolic rate (RMR), and other metabolic parameters during weight loss and weight regain over the two years the participants were on the study diet.
Higher baseline levels of PFASs were significantly associated with a greater weight regain, primarily in women. On average, women in the highest tertile of PFAS concentrations regained 1.7–2.2 kg more body weight than women in the lowest tertile.
Higher baseline plasma concentrations of PFASs, especially PFOS and perfluorononanoic acid (PFNA), were significantly associated with greater decline in RMR during the first six months and less increase in RMR during the period when participants on average regained weight (6–24 months).
Overall the study found that higher baseline PFAS concentrations were associated with a greater weight regain, especially in women, possibly explained by a slower return of RMR levels.
“These data provide initial evidence suggesting that PFASs may interfere with human body weight regulation and counteract efforts to maintain weight loss in adults,” noted the authors.
Seán Ottewell is Chemical Processing's Editor at Large. You can email him at firstname.lastname@example.org.