The Globe and Mail

Exposure to atrazine, a commonly used weed killer, increases the risk of reproductive problems in a wide range of animals, says a new review study that analyzed research from around the world.

In earlier studies, various scientists have concluded that the herbicide has gender-bending properties. For instance, some studies showed that male frogs could be turned into females by exposing them to small amounts of atrazine at critical points in their development. But the findings were disputed – especially by the chemical industry.

In response, Tyrone Hayes, a professor of integrative biology at the University of California at Berkeley, urged others studying atrazine to pool their work into a single comprehensive study.

In total, 22 scientists from North and South America, Europe and Japan contributed to the new study that was published this week in the Journal of Steroid Biochemistry and Molecular Biology.

Dr. Hayes, the lead author of the study, says the research reveals a common association between exposure to the chemical and the “feminization” of male gonads in many animals – including amphibians, reptiles, fish and mammals.

“No science is perfect, but all this research from around the world, done independently in controlled conditions and field studies, points to the same thing,” he said. “It doesn’t matter if you are a fish or a frog, a cat or a dog, if you are exposed to atrazine, there is a problem.” It has huge implications for humans as well, he added.

Val Beasley, a co-author of the study and professor emeritus at the University of Illinois at Urbana-Champaign, noted that the chemical has been shown to contaminate groundwater, surface water and even rain (due to dust particles blown into clouds).

“We have to ask ourselves whether we want to continue to be exposed to something like this,” said Dr. Beasley.

European countries have already banned atrazine, but it is still widely used to kill weeds in agricultural areas – especially corn fields – in Canada, the United States and more than 60 other countries.

Olivia Caron, a spokesperson for Health Canada, said in an e-mail that the federal agency has received a copy of the study. “Should validated data raise concerns for the use of atrazine in Canada, Health Canada will take action as necessary to protect the health and environment of Canadians. ’’

Dr. Hayes said the herbicide affects many biological processes – not just reproductive systems. With input from more that 40 international scientists, he is already working on a bigger study that explores the impact of atrazine on animal and human health.