Even embryos - here a blastocyst - show the same changes in the genome as the mother sows. (Image: ETH Zurich)
“We didn’t find any serious impact on the health of the adult offspring; we saw only slight changes, such as in bone density and the ratio of fat to muscle mass,” Ulbrich explains. However, it remains unclear what long-term effects the epigenetic changes might have, and whether the interaction of the many EDCs humans are exposed to on a daily basis render the situation more acute.
“There is an urgent need to observe this phenomenon over several generations in a long-term study,” says the ETH professor. “Epigenetic changes can emerge within just one generation, but in certain circumstances they will continue to be transmitted to succeeding generations. We can already clearly demonstrate that hormones, even after a brief exposure period and in very small amounts, can have a measurable effect,” she concludes.
Based on these results, Ulbrich, an expert in reproductive physiology, is calling for a re-assessment of the acceptable daily intake value and the “no observed effect level” dosage. She notes that pigs’ hormonal changes during pregnancy closely resemble those in humans, so the results of the study are highly applicable to humans; they may even be more appropriate than findings from a study of, say, mice.
“At the moment, recommended threshold levels are probably too high,” Ulbrich says. No matter how tiny the oestrogen dosage, the epigenetic changes she and her team observed clearly evidenced that the test subjects had been exposed to an EDC. She continues: “How exactly that resulted in the changes and what impact these changes will have in the long run requires closer study. The sensitivity of embryos in the early days of pregnancy should under no circumstances be underestimated.”
