The sex of painted turtles (Chrysemys picta), native to fresh waters of North America, is normally determined by the temperature the eggs are exposed to during development, but new research shows the commonly used hormone disrupting chemical bisphenol A (BPA) can disrupt this process. BPA, which is present in a number of household products including food can linings and till receipts, was found to disrupt male turtle development at levels found in polluted environments.
The research was a collaboration between US researchers at the University of Missouri, Westminster College, the US Geological Survey and the Saint Louis Zoo Institute for Conservation Medicine. In the press release for the study, Dawn Holliday, one of the researchers says :
“Normally, the painted turtle’s sex is determined by the temperature of the environment during their development in the egg—cooler temperatures yield more male turtles, while warmer temperatures mean females are more likely to develop”
“However, when turtle eggs are exposed to environmental oestrogens, their sex is no longer determined by the temperature, but rather by the chemical to which they’re exposed.”
The study found that when treated with levels of BPA which can be found in polluted environments, eggs incubated at the ‘male’ temperature (26 °C) produced turtles of which 30% or more had female-type tissue in their gonads.
“Turtles are known as an “indicator species” because they can be used as a gauge for the health of the entire ecosystem. By understanding the possible effects chemicals have on turtles, researchers might be able to understand the possible effects the chemicals have on other species, even humans” Holliday added.
This study is only one of many that have shown the profound impacts that hormone, or endocrine disrupting chemicals (EDCs) could have on wildlife. There are also many cases where these impacts have been proven. For example, a joint report by the World Health Organisation and the United Nations Environment Programme found a large number of examples of hormone disruption in wildlife, which included:
- The well-known case of the pesticide DDT thinning eggshells of birds of prey that resulted in severe population declines across North America and Europe.
- Exposure of marine snails to tri butyl tin (TBT), a biocide used in antifouling paints, which caused masculinization and worldwide declines of marine snails.
The impact of EDCs such as BPA is not limited to wildlife, and human health is also of concern. A study by the European Environment Agency, researching the impacts of endocrine disruptors on wildlife and people found that:
“[In the past 10 years] laboratory studies have shown that a broad range of species are susceptible to EDCs; for many species, strong evidence exists to indicate that endocrine disruption is a widespread phenomenon in wildlife populations …
The symptoms reported appear to mirror those observed in the human population, indicating that the human and wildlife evidence should be considered in parallel when assessing whether EDCs contribute to endocrine diseases and disorders.”