Study confirms link between herbicide atrazine and reproductive problems
Exposure to the chemical atrazine triggers reproductive dysfunction in animals, a new international study confirms. Presenting their study in The Journal of Steroid Biochemistry and Molecular Biology, scientists from Asia, Europe, and North and South America reviewed the evidence of a link between exposure to the herbicide used in over 60 countries worldwide and reproductive problems in mammals, amphibians, fish and reptiles. The United States in particular reports a high use of atrazine: over 75 million pounds of it are used on various crops including corn. This herbicide is also the most commonly detected pesticide contaminant of groundwater, surface water and even rain in the United States. For the purposes of the report, the team evaluated studies linking atrazine exposure to abnormal androgen levels in mammals, amphibians, fish and reptiles, along with studies linking exposure to atrazine to the 'feminisation' of male gonads in various animals. Their findings show that no less than 10 studies found that being exposed to atrazine will in fact trigger the feminisation of male frogs. In some cases, the sex of the animal is even reversed. Professor Val Beasley of the University of Illinois at Urbana-Champaign in the United States, one of the authors of the study, and his team discovered that the male frogs that came into contact with atrazine in the wild had a higher risk of having both male and female gonadal tissue than did frogs living in a herbicide-free environment. Citing a 2010 study carried out by Tyrone Hayes from the University of California, Berkeley in the United States, Professor Beasley says: 'Atrazine exposure in frogs was linked with genetic males becoming females and functioning as females. And this is not at extremely high concentrations. These are at concentrations that are found in the environment.' This latest report highlights the disruptions of hormone function and sexual development reported in studies of the various animals, and even human cells exposed to this herbicide. The results confirm that atrazine exposure triggers various modifications including changes in the expression of genes involved in hormone signalling, interferences with metamorphosis, inhibitions of key enzymes that regulate the production of oestrogen and androgen, and the impact on the normal reproductive development and functioning of males and females. 'One of the things that became clear in writing this paper is that atrazine works through a number of different mechanisms,' says Professor Hayes, the lead author of the report. 'It's been shown that it increases production of (the stress hormone) cortisol. It's been shown that it inhibits key enzymes in steroid hormone production while increasing others. It's been shown that it somehow prevents androgen from binding to its receptor.' Says Professor Beasley: 'Cortisol is a non-specific response to chronic stress. But guess what? Wildlife in many of today's habitats are stressed a great deal of the time. They're stressed because they're crowded into little remnant habitats. They're stressed because there's not enough oxygen in the water because there are not enough plants in the water (another consequence of herbicide use). They're stressed because of other contaminants in the water. And the long-term release of cortisol causes them to be immunosuppressed.' While some studies show neither effects nor different effects of exposure to atrazine, the studies are not all the same. 'There are different species, different times of exposure, different stages of development and different strains within a species,' Professor Beasely points out. Professor Hayes concludes: 'I hope this will stimulate policymakers to look at the totality of the data and ask very broad questions. Do we want this stuff in our environment? Do we want - knowing what we know - our children to drink this stuff? I would think the answer would be no.' Scientists from Argentina, Belgium, Brazil, Canada, Croatia, Japan, the United Kingdom and the United States contributed to this study.For more information, please visit: The Journal of Steroid Biochemistry and Molecular Biology:http://www.journals.elsevier.com/the-journal-of-steroid-biochemistry-and-molecular-biology/University of Illinois:http://www.uillinois.edu/
Countries
Argentina, Belgium, Brazil, Canada, Croatia, Japan, United Kingdom, United States
