Prenatal forever chemical exposure may affect puberty timing in children

An EHU-University of the Basque Country and Biogipuzkoa Health Research Institute study has linked certain chemicals measured during the first trimester of pregnancy to the subsequent onset of puberty in the children.

Within the framework of the INMA project, which studies the impact of environmental pollutants on pregnancy and child development, researchers analysed the concentrations of chemicals known as PFAS measured in the mother's blood, and the onset of puberty in girls and boys. The study showed that certain types of PFAS may be slightly associated with the early or late onset of some pubertal characteristics.

The changes from childhood to adolescence occur during puberty. In recent decades, there has been an increase in the phenomenon of early puberty. The scientific community is studying the issue from various perspectives; for example, it is known that early puberty tends to be associated with body fat accumulation, and that puberty tends to start earlier in countries with warmer temperatures. Puberty is largely regulated by the endocrine (hormonal) system, and a child's prenatal exposures do have an impact on the process. Indeed, exposure to chemicals that affect the endocrine system before birth can influence a child's hormonal signalling and the timing of puberty.

PFAS are some of the substances that affect the endocrine system and are known as endocrine disruptors:

Among other things, they are capable of triggering or stopping the metabolic mechanisms that our hormones normally set in motion." 

Sara López de Calle, researcher

PFAS are known as forever chemicals because they do not degrade easily and because they accumulate in the environment and in organisms. They are synthetic perfluoroalkyl and polyfluoroalkyl compounds, and nowadays, thousands of PFAS are used in many sectors (food processing, textiles, the manufacture of health products, etc.). "PFAS remain in our bodies for a long time: some of them take five years before half their concentration has disappeared from our bodies, while others take over 60 years," explained Dr Amaia Irizar.

Few epidemiological studies have been conducted on the exposure to PFAS before birth and their potential effects on the development of puberty. Researchers from the EHU-University of the Basque Country and the Biogipuzkoa Health Research Institute in fact measured the concentrations of the four most abundant PFAS commonly found in the blood of pregnant women during the first three months, and linked them to changes in their children's subsequent development of puberty. The research was conducted within the framework of the project known as INMA (Infancia y Medio Ambiente), a Spanish network of researchers who investigate how the growth and development of the foetus, the newborn and the child are affected by air, water and food contaminants.

So they explored whether children's prenatal exposure to PFHxS, PFOA, PFOS and PFNA was associated with an earlier onset of puberty in 492 mother-daughter and 475 mother-son pairs. "We analysed how each PFAS, individually and all four together (as a mixture), are associated with early puberty; what is more, we distinguished between girls and boys, and also took the children's body mass index into consideration," the researchers said.

No general trend

The researchers did not detect a general trend between these substances and a child's development: "We saw that as the concentration of certain PFAS increases, the likelihood of early puberty also increases; however, depending on the type of PFAS, we found different associations in boys, in girls, and at different stages of pubertal development," the researchers explained.

For example, in both sexes they found a greater tendency for puberty to be earlier in children when the concentrations of the four PFAS in the maternal blood (when all four were analysed together) were higher, and this association was significant for boys. Regarding PFHxS, it was associated with a higher risk of early adrenarche in girls (i.e., the early onset of the stage that causes changes in hair, skin and odour). The researchers noticed that puberty could kick in slightly earlier in the boys with higher maternal PFOS concentrations in the maternal blood; however, as for the girls, they found that they might experience delayed gonadarche (the phase of changes relating to the sex glands). "That is logical, as in the end boys and girls have different hormonal development," they explained. In any case, they were at pains to clarify that the links they found are not "very high, either, in other words, we did not conclude that the likelihood increases significantly".

The researchers paid particular attention to the analysis according to weight: they found that in cases where there was an association between a PFAS and the onset of puberty, this association increased in children who were overweight or obese. In other words, "if puberty kicked in earlier in children exposed to a PFAS, the effect was greater in overweight children", they explained.

So "the results have not provided conclusive evidence to link prenatal PFAS exposure with the onset of puberty; however, the evidence obtained is consistent with endocrine disruption that PFAS may bring about, and justifies further research," the researchers clarified. This work adds to the body of evidence on PFAS; until now, few cohort studies have been conducted on this topic "to see whether exposures during pregnancy might have some effect on the onset of puberty in children". Furthermore, until now, few studies have examined a group of PFAS together. So given the impact and ubiquity of PFAS in biology, the researchers said that "bigger, long-term studies are needed to clarify these associations and the consequences they may have in terms of public health".