A common pesticide that turns boy frogs into girls should get Albertans to think twice about how we grow our food, says a prominent scientist.
About 50 Edmonton-area residents went to the Telus Centre at the University of Alberta Wednesday night for a talk by Tyrone Hayes, a renowned professor of integrative biology from the University of California, Berkley. The talk was part of the university's Toxic Bodies lecture series on how chemicals like pesticides affect people.
While previous talks focused on chemicals in general, this one zoomed in on atrazine – a herbicide commonly used in corn production in the U.S. and around Ontario.
Hayes shot to fame about 20 years ago when he discovered that atrazine turned male frogs into female ones. His research since then has inspired several lawsuits and legal efforts to ban the substance.
"There is enough atrazine in rainwater to chemically castrate a frog," he said, citing his research. Atrazine appears to be contributing to a global population crash in frogs, he continued, and to higher cancer rates in humans.
"We're using 80 million pounds [a year] of a chemical that's not allowed in the European Union," he said, referring to American usage, and all so farmers can boost their corn yields by about 1.2 per cent.
"We're really going to have to make changes in how we decide what's safe and what's not safe," he said.
Sex-changing frogs
A life-long frog fan, Hayes said he first hit upon the frog-herbicide connection 20 years when the company now known as Syngenta asked him to use African clawed frogs (a common experimental model) to measure the environmental impacts of atrazine.
The results were stunning. Hayes and his team found that male frogs exposed to this herbicide at very low levels – about 0.1 parts per billion, or one drop in 5,200 bathtubs – developed male and female reproductive organs and had testosterone levels comparable to those of females.
Further experiments, one of which involved putting the frogs in a kiddie pool, found that atrazine-treated male frogs almost never mated with females, often tried to mate with other males, and developed brain structures similar to females, Hayes said.
"They think they're female," he said.
They also had little sperm (and occasionally eggs) in their testes.
Researchers have since replicated these effects in wild leopard frogs, rats, birds, fish and many other vertebrates. This research has prompted Europe to effectively ban the use of atrazine and Syngenta to spend millions trying to discredit Hayes.
Of frogs and men
"A typical farmer might be using this stuff at levels that are 290 million times higher what we use in the lab," Hayes notes, referring to the recommended use level in agriculture. The amount of atrazine allowed in drinking water under U.S. law is 30 times higher than what he used in his experiments.
Other researchers have found that women who drink atrazine-contaminated water were more likely to get breast cancer, Hayes said, while men with the substance in their urine had lower sperm counts. Men in atrazine factories have 8.4 times more prostate cancer than average. What we don't know, he cautioned, is the amount of exposure that's required for these effects to kick in.
But because atrazine is valuable to corn farmers, Hayes argued, there's great resistance to its regulation.
"As one farmer put it to me, 'I know it's bad, but if I don't use it this year, my neighbour will own my farm next year,'" he said.
Hayes' work is an example of what happens when science meets entrenched political interests, said talk organizer Debra Davidson. It took decades of research to find these problems with atrazine, she noted.
"What does that say about the numerous other pesticides that are also in regular use that aren't going through the same amount of research attention?" she wondered.
The next talk in the Toxic Bodies series, which will feature Slow Death by Rubber Duck author Bruce Lourie, is on April 4 at the U of A's Telus Centre at 6:30 p.m. Call Davidson at 780-492-4598 for details.
