The public debate on endocrine disrupting chemicals (EDCs) – exogenous substances that have the same or similar effects as endogenous hormones – has been going on for some time. Chemicals such as bisphenol A or phthalates, the latter of which are used to soften plastics, may be connected to rising infertility rates among men and women.

In an experiment with pigs, researchers from ETH Zurich and the Technical University of Munich have demonstrated for the first time that the administration of even extremely low doses of an endocrine disruptor – in this case, an endogenous oestrogen – leads to epigenetic changes in a pregnant sow’s DNA. Moreover, these changes were also observed in the sows’ embryos, and similar changes were even evident after the offspring had reached adulthood. The study was recently published in the journal Scientific Reports.

A time window of increased sensitivity

“EDCs, especially oestrogens, are highly effective even at very low doses,” says Susanne Ulbrich, Full Professor of Animal Physiology at ETH Zurich. Whether endo- or exogenous chemicals have an effect, and how strong that effect is, also depends on the point in time during which the exposure occurs. “For example,” Ulbrich explains, “the body is particularly susceptible to external disruptive hormonal influences during the embryonic phase of early pregnancy.”

Ulbrich and her colleagues examined exactly such a time window in their study with pigs: to simulate the intake of EDCs via drinking water or food, they exposed pregnant sows to varying doses of oestradiol-17β, a natural oestrogen, via their daily feed either over the course of the whole gestation period or only during the first ten days after fertilisation.