Marsupials are experiencing devastating population declines across Australia, with 21 per cent of native mammals currently threatened with extinction. As their habitat becomes more restricted, marsupials are pushed into agricultural areas and forestry plantations, attracted to the food resources and rare permanent water sources. This shift may increase their risk of exposure to agricultural contaminants, such as pesticides.
The herbicide atrazine is of particular concern due to its ability to disrupt the signals from reproductive hormones in a broad range of vertebrates, including fish, reptiles, frogs and rodents. Atrazine is of such concern that it has been banned across the European Union since 2003, due to its known impacts on the health of wildlife and potential impacts on humans. However atrazine is used extensively in Australia, on cereal crops and in forestation to prevent the growth of weeds, with approximately 3000 tons used on crops annually.
Researchers at the University of Melbourne investigated whether atrazine disrupted development of the reproductive organs in marsupials. After exposure to atrazine at 450ppm in the drinking water during gestation and lactation, male offspring had a 20% reduction in penis length and altered expression of genes involved in testis development. This indicates that the hormone environment had been disrupted during a critical window of reproductive development.
This is the first study to show that endocrine disruptors (chemicals that disrupt normal hormone signalling) are able to affect developing marsupial pouch young through gestational and lactational exposure. These data raise major concerns for the use of pesticides in areas with vulnerable or endangered marsupial populations and illustrates the need for more stringent guidelines surrounding the use of known endocrine disrupting chemicals such as atrazine in Australia.
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Written by Laura Cook and Liza O’Donnell