Women with higher levels of so-called “forever chemicals” in their blood have a 40% lower chance of becoming pregnant within a year of trying to conceive, according to the first known study on the effect of PFAS on female fertility. PFAS, or per- and polyfluoroalkyl substances, have been found in almost everyone tested for them, with 99% of people in the US contaminated. The research was conducted in Singapore, where contamination levels are lower, but the scientists still found a strong correlation with reduced fertility. PFAS are a group of chemicals that are water- and oil-resistant, and are used in a vast array of products, from non-stick cookware and food containers to clothing and furnishings. They are often called forever chemicals because they are very slow to break down in the environment and are now widely found in water and soil. They have been increasingly linked to health damage, including cancers and liver, kidney and thyroid disease. Some PFAS have been banned but more than 12,000 chemicals in the class have been produced. The scientists who conducted the research called for the entire group of chemicals to be regulated. “Our study strongly implies that women who are planning pregnancy should be aware of the harmful effects of PFAS and take precautions to avoid exposure to this class of chemicals,” said Dr Nathan Cohen, lead author of the research at the Icahn school of medicine at Mount Sinai in New York. One in six people worldwide are affected by infertility, according to a World Health Organization report published on Monday. Dr Damaskini Valvi, an assistant professor at Icahn Mount Sinai, said: “We are currently facing a global PFAS contamination problem. Stopping producing PFAS in the first place is the only way that can help us avoid exposure completely. “In the meantime, there are a few things that we can do at the personal level to reduce to some extent our own exposure,” , which she said included using special water filters and avoiding products containing PFAS. The study, published in the journal Science of the Total Environment, included more than 1,000 women of child-bearing age in Singapore who were trying to conceive. It found a range of PFAS levels in the women’s blood and assessed the chemicals’ impact at each quarter between the lowest and highest exposure level. Those women with PFAS mixture levels one quarter higher than the average had a 40% lower likelihood of becoming pregnant within a year. These women also had a 34% lower chance of having a live birth within 12 months. The effect of PFAS levels on fertility was greater when they were considered as a mixture, rather than individually. “That makes sense, because multiple chemicals may act together to impact our health at a much greater level than one chemical,” said Valvi. This type of study does not shed light on how PFAS affects fertility, but previous work has shown the chemicals impact hormones and egg production and function, as well as being linked to polycystic ovarian syndrome. “We have really strong evidence from the laboratory, suggesting that PFAS can affect fertility in the female reproductive system,” Valvi said. The study took account of the women’s age, education and smoking status, as well as how many children they had already had. PFAS are known to affect male fertility but the researchers did not have information on PFAS levels in the women’s partners. Valvi said future studies that assessed both parents would be useful. PFAS also affect the health of the mother and baby, Valvi said, such as preeclampsia and neurodevelopmental delays. “Many PFAS have been detected in cord blood, the placenta, and breast milk. Preventing exposure to PFAS is therefore essential to protect women’s health as well as the health of their children,” she added. The link between PFAS exposure and reduced fertility in women was also reported in an analysis of 13 earlier studies, which was published in January and focused on individual chemicals. “This finding could partially explain the decline in female fertility,” said the authors of the analysis at Southeast University in Nanjing, China Five EU countries proposed a ban on 10,000 PFAS chemicals in January. In the US, President Joe Biden is taking action against some forever chemicals and the UK has proposed phasing out some of them. Only banning a subset of the chemicals was not good enough, said Valvi, because there were “thousands of PFAS used out there”. In March, Canadian scientists revealed a new way to capture and destroy PFAS.