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Environment and sustainability

Waterproofing and non-stick pans may lead to earlier puberty among girls

Waterproof raincoats and non-stick pans make our everyday lives more practical. Unfortunately, some of the perfluoroalkyl substances that provide the practical benefits end up in the water and air and may harm our health. A new study appears to show that these substances are associated with girls starting puberty prematurely. Boys also seem to be affected by the substances. The researchers hope that manufacturers will improve at investigating the potential long-term effects before using such substances.

Children start puberty today much earlier than they did 150 years ago. Better living standards have caused much of this, but even though they have not changed significantly in recent years, research shows that the age at which puberty starts has continued to decline. A Danish research project has now shown that the perfluoroalkyl substances in our environment may play a role in this trend. The substances are in our environment because they are used in many things we use every day: packaging, blankets, jackets and pans.

“These substances are present in the air, water and dust that surround us. We measured the concentration of these substances in pregnant women’s blood and showed that the children of the women who have the highest concentrations start puberty earlier, and this may affect their health in the long term. The changes seem to apply to both the first generation of these substances but also to the new generations,” explains the study’s first author, Andreas Ernst, PhD student, Department of Public Health, Aarhus University.

New substances have the same effect as the old ones

The study is part of the project Better Health in Generations, which collected data from 92,000 pregnant women in 1996–2003. Since then, the children resulting from these pregnancies have been regularly followed up with questionnaires. Since 2012, 22,341 of the children born in 2000–2003 have been invited every 6 months to answer questions about their pubertal development, such as whether they had begun to develop breasts and pubic hair.

“We therefore had a unique opportunity to compare the children’s responses with the concentration of the perfluoroalkyl substances in their mother’s blood samples while they were pregnant, and this indicated a rather clear association. If the mothers had a high concentration of these substances in the blood, the girls started puberty 4 months earlier on average.

For the boys, the data were slightly more difficult to interpret, since some of the perfluoroalkyl substances in the blood were associated with starting puberty 1 month earlier and others were associated with starting 4 months later. Nevertheless, both girls and boys differed significantly in the age at which puberty started according to the concentrations of these substances. And all the various perfluoroalkyl substances – new and old – seemed to affect when puberty started.

“We had hoped that the second generation of these substances had less harmful effects than the old ones, but unfortunately this does not seem to be the case. One might hope that the rules for introducing chemical compounds into general use would be subject to the same strict requirements as, for example, new medicine,” explains another main author, Cecilia Ramlau-Hansen, Professor, Department of Public Health, Aarhus University.

Important for children’s health throughout life

The new study suggests that more thorough toxicological studies would be appropriate before new substances are approved for use. The new findings are worrying in any case, since previous studies suggest that earlier puberty is associated with increased risk of overweight, cardiovascular diseases, diabetes and some types of cancer, such as breast cancer.

“However, more research is still needed to explain the precise mechanisms that lead to the changes in the puberty profile. One explanation may be epigenetic effects, since we know that substances in our environment and food can affect the surface of DNA chemically.”

The chemical modifications of DNA greatly affect which genes are ultimately expressed and when. Evidence also suggests that the substances to which a fetus is exposed during pregnancy greatly affect the child’s health throughout life.

“If the perfluoroalkyl substances actually chemically change our DNA, this could be a plausible explanation for what we have found. However, it is still too early to determine the precise underlying mechanism between the chemical compounds, the expression of our DNA and the physiological changes we observe.”

Exposure to perfluoroalkyl substances during fetal life and puberty development in boys and girls from the Danish National Birth Cohort” has been published in Environmental Health Perspectives. In 2014, the Novo Nordisk Foundation awarded a grant to Cecilia Ramlau-Hansen for the project Birth Outcomes and Genital Malformations in Children of Mothers with Pregnancy-Associated Cancer: A Nordic Epidemiologic Cancer Project.

Cecilia Ramlau-Hansen
Professor
It remains unsettled whether prenatal exposure to perfluoroalkyl substances (PFASs) affects human reproductive health through potential endocrine disruption. Perfluoroalkyl substances (PFASs) cover a group of synthetic chemicals that induce water, oil, and dirt resistance, and these are used in the manufacturing of a variety of everyday consumer products. The substances are highly environmentally persistent and have long half-lives, thus having the disadvantage of accumulating in humans through various exposure routes, including drinking water, diet, dust, and air. PFASs cross the placental barrier and were recently detected in placental and fetal tissue from legally terminated pregnancies. This has raised concerns about the potential adverse effects of prenatal exposure to PFASs on later health, including reproductive health. These concerns are supported by an emerging number of in vitro and animal studies, proposing mechanisms by which PFASs may interfere with the endocrine system. We aimed to explore the associations between prenatal exposure to several PFASs and various aspects of pubertal development in boys and girls.