The trend worldwide is for children to reach puberty earlier now than before. One of the main theories for why this happens are the possible effects from environmental contaminants that can mimic and disrupt hormones and signals in the body. (Illustration photo: Heiko Junge/NTB)

Girls who had a lot of environmental toxins in their blood started menstruating earlier

A study of young people from northern Norway finds a link between high levels of PFAS in their blood and early menstruation.

One of the theories behind why the age of puberty onset is earlier now than before is the influence of environmental contaminants such as PFAS.

The link between PFAS and puberty has not been well studied, according to the researchers behind a recently published study on the topic in the Environmental Research journal.

The researchers in the Northern Norwegian study Fit Futures collected blood samples and questionnaires from over 900 girls and boys aged 15-19.

Almost 16 percent of the girls in the sample had their first period before they turned 11, considered early onset menstruation. These girls also had the highest levels of PFAS in their blood.

Man-made environmental poisons

PFAS are man-made chemicals that can be found everywhere, including in your body.

PFAS are water, stain and grease repellent and are used to make products such as ski waxes, make-up, non-stick pans and impregnated sportswear. They leak into nature and contaminate drinking water, vegetables, animals and fish.

One year ago, Norway helped put forward a proposal to ban PFAS in the EU.

“PFAS are some of the most worrying contaminants we surround ourselves with,” said Espen Barth Eide, then-Minister of Climate and the Environment (in Norwegian).

Over 10 000 different PFAS have been identified, and we know very little about most of them. The ones that have been researched the most have been shown to be carcinogenic, weaken the effect of vaccines, and to inhibit foetal development.

It is unclear how puberty may be affected by PFAS, but one theory is that, similar to some other environmental contaminants, they can mimic or inhibit the effects of testosterone or oestrogen and disrupt signals that are important for puberty onset.

Disrupts endocrine system

“Ours is one of an increasing number of studies indicating that these substances that we surround ourselves with disrupt our bodies,” says Guri Grimnes, a senior physician and professor at UNN and UiT–Norway's Arctic University. She is one of the researchers behind the study.

However, Grimnes emphasizes that the researchers cannot confirm that high levels of PFAS are the cause of early onset menstruation. The young people in the study have not been followed over time. They have answered questions and given blood samples at only one point in time. What the researchers can say is that they have found a link.

The researchers also found an association between high levels of PFAS in the blood and an imbalance in the steroid hormones produced in the adrenal glands.

The adrenal glands of boys with high levels of PFAS appeared to produce more stress hormones and fewer male sex hormones than those who did not have high levels of PFAS in their blood.

Ingvild Halsør Forthun studies the link between PFAS and pubertal development at the University of Bergen.

“For the girls, it was the opposite, where the adrenal glands of girls with high PFAS levels in their blood produced more male sex hormones and fewer stress hormones. More research is definitely needed here before we can be sure of anything,” says Grimnes.

“But our results indicate that these substances do affect our endocrine system.”

Also related to late onset menstruation

“This is an exciting study, but the connection between PFAS and puberty is still unclear,” says Ingvild Halsør Forthun.

“There are studies that point in both directions – that PFAS levels are related to both late and early onset puberty,” she says.

Forthun is currently working on a PhD on this topic as part of the Bergen Growth Study 2 (Vekststudien).

The growth study was carried out in 2016 and has established benchmarks for normal pubertal development in Norway. Compared to the Bergen Growth Study 1 from 2003 to 2006, the researchers have seen the average age for first menstruation decrease by 2.8 months.

Forthun's first study from the project found that one in five children had higher PFAS levels than what is regarded as safe.

The results of what she found about the association between PFAS and pubertal development will be published this autumn. More than 1000 children were examined at various stages of puberty for the study.

“The worldwide trend is towards earlier puberty and earlier breast development, and some studies have also found a lower age for first menstruation. Most of the available data is on girls, and that is where we see the trend most clearly,” says Forthun.

The trend arose at the same time as increased childhood obesity.

“But the phenomenon of early puberty occurs in all groups, both normal weight and overweight individuals. So obesity alone doesn’t explain it. Environmental contaminants are an important theory,” says the researcher.

Most studies are on pubertal development and menstruation, because it is an easy measure to ask about, and most girls remember when they had their first period. The physical changes of puberty for boys are less clear. Remembering when your voice changed, for example, is often not as precise.

Tolerance limit greatly lowered in 2020

Line Småstuen Haug works with environmental contaminants at the Norwegian Institute of Public Health. In 2020, she was part of a working group in EFSA, the EU's body for food safety, which carried out a risk assessment of PFAS.

The tolerance limits for PFAS were then lowered considerably, because updated research has shown that they are more dangerous than previously thought, says Småstuen Haug.

The reasoning at the time was mainly that PFAS causes vaccines to work less well. It was not possible to come to a conclusion on PFAS’ effect on hormones and puberty.

The study from Northern Norway is interesting, Småstuen Haug says. The study is large, with almost a thousand participants.

The problem is, as the researchers themselves also point out, that it is not possible to draw conclusions about causation. No samples exist of the girls' blood before they had their first period.

“When you measure PFAS and hormones in the same sample, you can’t in principle know whether PFAS are affecting the hormones or hormones are affecting PFAS,” says Småstuen Haug.

Lower levels today

Menstruation onset in Norway

In 1861, the average age for first menstruation was 15.6 years.

By 1940 it had dropped to 13.3 years.

The age of menstruation onset was stable at just over 13 years until the 2000s.

The Bergen Growth Study 2 found that, the average age for menstruation onset had dropped to 12.9 years among children measured in 2016.

Source: Starter puberteten tidligere enn før? (Does puberty start earlier than before?) (in Norwegian)

Småstuen Haug says that one way that PFAS are excreted from the body is by losing blood, which girls do when they menstruate.

PFAS levels also change as children mature because the growing body has more blood. Measurements often find the highest levels of PFAS in younger children. They have the least amount of blood in which to distribute PFAS and even ingest PFAS through breastfeeding.

“Measuring the blood level a few years after your first period is therefore not necessarily representative of what it was before menstruation onset,” Småstuen Haug says.

The Norwegian Institute of Public Health researcher also points out that the measurements stem from 2010 to 2011.

“If we measured now, the levels would most likely be slightly lower, because we’ve been observing a downward trend since 2000. In any case, it’s unlikely that they would be any higher,” she says.

Småstuen Haug is one of the researchers behind a study which found that almost a third of Norwegian children had levels of PFAS in their bodies that were higher than what is considered safe. The figures were from 2016 and 2017. New data is being collected now that will be able to provide information about current levels.

Fertility in the future

The next study from Fit Futures in Northern Norway will be able to report on PFAS exposure over time.

The young people in the study were followed up and re-tested when they were 18 years old, and again when they were 26-27 years old. Sex hormones, menstruation and levels of environmental contaminants were mapped.

Grimnes and her colleagues have also collected sperm samples from the men in the study.

The aim is to be able to offer more definitive conclusions about how exposure to environmental contaminants in the teenage years affect future fertility.


Translated by Ingrid P. Nuse

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