A study by researchers at Karolinska Institutet in Sweden shows PFAS industrial chemicals, which are used in many consumer products, pass through the placenta throughout pregnancy to accumulate in foetal tissue. Further research is needed to ascertain the effect on the foetus.
The PFAS (perfluoroalkyl substances) group comprises thousands of human-made chemicals, which, thanks to their water- and grease-resistant properties, are used in everything from frying pans and food packaging to clothes, cleaning agents and firefighting foams.
“We’ve focused on six of these PFAS substances and found that all appear to the same extent in foetal tissue as in the placenta,” says Richelle Duque Björvang, doctoral student at the department of clinical science, intervention and technology, Karolinska Institutet. “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.”
PFAS levels were highest in the lung and liver tissue, in some cases as high as in adults, and lowest in the brain. The study included tissue samples from 78 embryos and foetuses aged 7 to 42 weeks, sourced from biobanks in Sweden and Denmark.
Amongst the six PFAS substances studied were PFOS and PFOA, which are the best known. PFOS was banned by the EU in 2008, and at the start of the year the European Food Safety Authority sharpened its appraisal of PFOS and PFOA and lowered the tolerable daily intake thousand-fold.
“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 Dr Pauliina Damdimopoulou, senior researcher at the department of clinical science, intervention and technology. “Today’s threshold values are based on an adult population rather than foetuses, which are much more susceptible.”
The accumulation of PFAS substances was also higher in male foetuses than female. “We know that there are slight differences in the function of the placenta depending on the sex of the foetus, which is something we need to do more studies on in relation to impact on fetal chemical exposures,” says Damdimopoulou. “We also need to find out what effects these substances have on different foetal organs.”
PFAS substances have been used since the early 1900s and are ubiquitous in our environment. “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,” continues Damdimopoulou. “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.”
Background: The persistent environmental contaminants perfluoroalkyl substances (PFASs) have gained attention due to their potential adverse health effects, in particular following early life exposure. Information on human fetal exposure to PFASs is currently limited to one report on first trimester samples. There is no data available on PFAS concentrations in fetal organs throughout all three trimesters of pregnancy.
Methods: We measured the concentrations of perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), and perfluorohexane sulfonic acid(PFHxS) in human embryos and fetuses with corresponding placentas and maternal serum samples derived from elective pregnancy terminations and cases of intrauterine fetal death. A total of 78 embryos and fetuses aged 7–42 gestational weeks were included and a total of 225 fetal organs covering liver, lung, heart, central nervous system (CNS), and adipose tissue were analyzed, together with 71 placentas and 63 maternal serum samples. PFAS concentrations were assayed by liquid chromatography/triple quadrupole mass spectrometry.
Results: All evaluated PFASs were detected and quantified in maternal sera, placentas and embryos/fetuses. In maternal serum samples, PFOS was detected in highest concentrations, followed by PFOA > PFNA > PFDA = PFUnA = PFHxS. Similarly, PFOS was detected in highest concentrations in embryo/fetal tissues, followed by PFOA > PFNA = PFDA = PFUnA. PFHxS was detected in very few fetuses. In general, PFAS concentrations in embryo/fetal tissue (ng/g) were lower than maternal serum (ng/ml) but similar to placenta concentrations. The total PFAS burden (i.e. the sum of all PFASs) was highest in lung tissue in first trimester samples and in liver in second and third trimester samples. The burden was lowest in CNS samples irrespective of fetal age. The placenta:maternal serum ratios of PFOS, PFOA and PFNA increased across gestation suggesting bioaccumulation in the placenta. Further, we observed that the ratios were higher in pregnancies with male fetuses compared to female fetuses.
Conclusions: Human fetuses were intrinsically exposed to a mixture of PFASs throughout gestation. The compounds were detected in all analyzed tissues, suggesting that PFASs reach and may affect many types of organs. Collectively, our results demonstrate that PFASs pass the placenta and deposit to embryo and fetal tissues, calling for risk assessment of gestational exposures.
Linn Salto Mamsen, Richelle D Björvang, Daniel Mucs, Marie-Therese Vinnars, Nikos Papadogiannakis, Chris H Lindh, Claus Yding Andersen, Pauliina Damdimopoulou