PFAS, now found in nearly all umbilical cord blood around the world, interfere with hormones crucial to testicle development
A new peer-reviewed Danish study finds that a mother’s exposure to toxic PFAS “forever chemicals” during early pregnancy can lead to lower sperm count and quality later in her child’s life.
PFAS – per- and polyfluoroalkyl substances – are known to disrupt hormones and fetal development, and future “reproductive capacity” is largely defined as testicles develop in utero during the first trimester of a pregnancy, said study co-author Sandra Søgaard Tøttenborg of the Copenhagen University hospital.
“It makes sense that exposure to substances that mimic and interfere with the hormones involved in this delicate process can have consequences for semen quality later in life,” Søgaard Tøttenborg said.
PFAS are a class of about 12,000 chemicals typically used to make thousands of products resistant to water, stains and heat. They are called “forever chemicals” because they accumulate in humans and the environment and do not naturally break down. A growing body of evidence links them to serious health problems such as cancer, birth defects, liver disease, kidney disease and decreased immunity.
The study, published on Wednesday in Environmental Health Perspectives, examined semen characteristics and reproductive hormones in 864 young Danish men born to women who provided blood samples during their pregnancies’ first trimesters between 1996 and 2002.
The study builds on others that found similar issues, but it is the first to look for exposure to more than two PFAS compounds and to assess exposure during early pregnancy, which is the male reproductive organ’s “primary developmental period”.
Researchers checked the mothers’ blood for 15 PFAS compounds, and found seven in large enough concentrations to include in the study.
Those mothers with higher levels of exposure more frequently raised adult men with lower sperm counts, as well as elevated immotile sperm levels, meaning their sperm did not swim. This exposure also increased the amount of non-progressive sperm – sperm that do not swim straight or swim in circles. Both issues can lead to infertility.
The ubiquitous chemicals are estimated to be in 98% of Americans’ blood, and they can cross the placental barrier and accumulate in the growing fetus. A recent analysis of 40 studies of umbilical cord blood from around the world found that PFAS were detected in all 30,000 samples collectively examined.
Infertility rates are on the rise worldwide, often for unclear reasons, Søgaard Tøttenborg said.
“The results of our studies are an important piece in that puzzle,” she added. “Equally important: the more we know, the more we can prevent.”

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