The World Health Organization has dropped a potential bombshell on the debate about the safety of atrazine.
Scientists at the United Nations agency concluded in a report released in early October that tap water can contain up to 100 parts per billion of the herbicide without adversely affecting human health.
The recommendation caught American pesticide experts off guard because many U.S. states use a standard of three ppb of atrazine in drinking water.
“I think we were surprised that it was as high as it was,” said Paul Moyer, a toxicologist with the Minnesota Department of Health.
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Jere White, executive director of the Kansas Corn Growers Association, said the WHO report is noteworthy because earlier this year the U.S. Environmental Protection Agency initiated a review of atrazine that focuses on the chemical’s impact on human and amphibian health.
“The strongest significance of it is yet another international agency has taken a look at the issue and determined that there’s really not an issue,” White said during a break from a meeting on atrazine in San Antonio, Texas.
“If you start stacking up, between Australia, the United Kingdom and a number of reviews that have taken place, the one consistent message is that the EPA got it right in 2006 when they re-registered the product.”
The EPA’s latest scientific review of the Syngenta product pre-empted its planned review scheduled for 2013.
The EPA said in a news release that the review would consider the newest and most relevant studies, including the potential link between atrazine and cancer and the herbicide’s impact on amphibians.
The pre-emergent herbicide is banned in Europe, and the EPA concluded in a 2003 report that an American ban would have a massive economic impact on U.S. farmers
“The total or national economic impact resulting from the loss of atrazine to control grass and broadleaf weeds in corn, sorghum and sugar cane would be in excess of $2 billion per year if atrazine were unavailable to growers,” it said.
An EPA conclusion that the herbicide is a threat to human or animal health would have a ripple effect on Canadian producers, said Clarence Swanton, a University of Guelph crop science professor who studied the economic value of atrazine for Canadian corn producers in 2007.
“If the EPA in their review decides that they want to ban it, then there will be huge pressure on Canada to follow suit,” he said.
Swanton estimated atrazine is worth $26 million a year to Ontario’s corn growers, based on its efficacy and its low price relative to other herbicides.
Atrazine has been available for 50 years, and most Canadian and American corn growers use it in combination with modern herbicides.
“A lot of our new chemistry, registered over the last several years, still relies on tank mixtures with atrazine to improve overall performance,” Swanton said. “A lot of the new chemistry has weaknesses that atrazine covers…. You might refer to it as almost the backbone of weed management in corn.”
He said the number of producers depending on atrazine could expand in the near future because glyphosate resistance is becoming more common in North America.
“With overuse of Roundup, we’re getting increased levels of weed species resistance to Roundup.”
While the WHO recommendation is an attention grabber, Moyer said the EPA dictates environmental policy in the United States.
“We’re more intent on some of the conclusions that the EPA might make here in the next few months.”
The Minnesota government completed its own assessment of atrazine in January.
State scientists analyzed water quality data going back to 1985 and determined that atrazine was not a threat to human or amphibian health, said Nila Hines, a pesticide specialist with Minnesota’s agriculture department.
“We really concluded that our state health standards and our state environmental standards are adequate,” she said. “They (the standards) are protective of both human health and aquatic life.”
Minnesota’s conclusion isn’t the final word on the chemical, Moyer noted. New studies are always underway and its reputed link to declining frog populations could affect the EPA’s decision.
“If you talk about setting a safe level for humans, for whatever chemical, that doesn’t mean that level might not be harmful for other species.”
All about atrazine
•Atrazine was first introduced in Canada in 1960. Since then, the herbicide has been used to control broadleaf weeds in corn, canola, low brush blueberries and other crops.
•The Canadian guideline for atrazine in drinking water is five parts per billion.
•Exposure to high levels in drinking water can cause nausea and dizziness. Studies in humans show evidence of an increased risk of ovarian cancer or lymphomas.
•Research published in 2010 by scientists at the University of Berkeley indicates that 2.5 ppb of atrazine in water can castrate male frogs and turn them into females that lay eggs. As a result, environmental groups have labelled atrazine as the gender bender herbicide.
