Scientists from five Polish universities exposed 300 tadpoles of the marsh frog Pelophylax ridibundus to very low concentrations of two endocrine-disrupting compounds (EDCs) — bisphenol A (BPA), which leaches into the environment from plastic containers, and ethinylestradiol (EE2), a synthetic estrogen used in contraceptives and hormone therapies. The concentrations matched levels currently detected in European surface waters.
The results were alarming, said Martyna Frątczak of Poznań University of Life Sciences, who led the study. In the group exposed to EE2, the sex ratio was severely skewed — roughly nine females to every one male, against a normal ratio of approximately 1:1. Some individuals also displayed intersex characteristics, with gonads containing tissue typical of both testes and ovaries.
"All indications are that some genetic males developed female characteristics under the influence of the compound. Critically, this effect appeared at an extremely low concentration — roughly one molecule of the compound per billion molecules of water", Frątczak said.
BPA did not affect sex ratios but proved damaging nonetheless. Histological analysis revealed significant degeneration and loss of reproductive cells in the testes of some males, which could impair fertility, while some gonads showed signs of delayed development.
Co-author Prof. Piotr Tryjanowski warned the findings pointed to a broader ecological problem. "Amphibians have long been treated as an early warning system for the environment. If we observe sexual development disorders in them caused by substances present in water, we are dealing with a real ecological problem. We are probably seeing only a fragment of a much larger phenomenon", he said.
The study was published in the journal Aquatic Toxicology and involved researchers from the universities of Poznań, Jagiellonian, Szczecin, Wrocław and Białystok.
(jh)
Source: PAP