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As U.S. growers wrap up planting an estimated 90 million acres of corn this spring, there’s a good chance many of those acres have something in common besides seed corn – an application of atrazine.

Discovered more than 50 years ago, 2-chloro-4-(ethylamine)-6-isopropylamine)-s-triazine or atrazine has become one of the most commonly used herbicides in the world. According to some counts, U.S. farmers apply around 76 million pounds a year.

But those applications could be in jeopardy if environmental groups such as the Natural Resources Defense Council succeed in their efforts to persuade EPA to phase out all uses of the product in the United States, including gardens and golf courses.

In a recent report entitled, “Still Poisoning the Well,” the NRDC repeated its claims that atrazine is responsible for pervasive contamination of watersheds and drinking water systems across the Midwest and Southern United States. The NRDC claims “thousands of drinking water systems may be unknowingly contaminated with atrazine.”

Representatives of Syngenta, the basic manufacturer of atrazine, have heard it all before. Some of them seem resigned to the fact they will have spent much of their careers defending the safety of atrazine.

“I’m proud to say atrazine is a tried and true herbicide that’s been used by American growers for over 50 years now,” says Chuck Foresman, technical brand manager for Syngenta. “And the reason why people use it is because it works and is safe.”

Foresman, who was interviewed following a Syngenta presentation at the Commodity Classic earlier this year, acknowledged that atrazine is well on its way to becoming one of the most studied herbicides in crop protection chemical history.

Despite its having been given a clean bill of health by EPA four years ago, the agency has announced it is taking yet another look at the herbicide’s safety record. Besides the NRDC’s April critique of atrazine, the National Academy of Sciences has also released a report echoing some of the NRDC’s claims.

“There are over 6,000 studies that have been looked at by the EPA over the last several years,” said Foresman. “In fact, in 2006, EPA decided to re-register, in other words, re-license the use of atrazine, and so it has come under close scrutiny.”

Syngenta toxicologists have looked at the National Academy of Sciences report, which refers to a study that claims atrazine appears to inhibit the reproductive development of a certain species of frogs. The study contains several flaws, according to Syngenta scientists.

“No. 1, we wonder if the results are really reproducible,” says Foresman. “In fact, the author of the article suggests these findings are not similar to previous test findings. No. 2, when you do toxicological studies you really should be looking at more than a single dose, and that’s what they did in this study, a single dose of atrazine that was used to expose these frogs.”

The scientists also question the lack of an internal positive control among the population. (An independent Scientific Advisory Panel set up by EPA has reviewed the findings and said there is not enough data to determine if atrazine affects amphibian development.)

“So there are several aspects of that study that Syngenta takes issue with,” says Foresman. “It was a bit of a sensational study. We don’t think it’s founded in good science, and Syngenta takes the approach that good science will prevail.”

The Scientific Advisory Panel’s findings haven’t stopped the NRDC from continuing its efforts to phase out atrazine. On its Web site, the NRDC claims that based on an analysis of atrazine monitoring data taken from 20 watersheds between 2007 and 2008, surface waters in the Midwest continue to be “pervasively contaminated” with atrazine.

It also cites findings that 18 of the watersheds were intermittently severely contaminated with at least one sample above 20 parts per billion of atrazine. “Nine had a peak concentration above 50 ppb, and three had peak maximum concentrations exceeding 100 ppb,” it said. (For more on the NRDC’s study, go to http://www.nrdc.org/health/atrazine/.)

Peak concentration is a term the NRDC keeps coming back to because average concentrations at the atrazine monitoring sites continue to fall below the 3 ppb upper limit set by EPA for drinking water.

“Our analysis of the data reinforces the fact that the monitoring schedule, set by drinking water regulations, fails to guard against high spikes in atrazine levels or even ensure that the EPA’s annual average limit on atrazine contamination is not being exceeded,” the NRDC says in its executive summary for the April report.

“Because public water systems are only required to take one to four samples per year, they are likely to miss a lot of the high spikes we found. This means the EPA is ignoring high spikes of atrazine in drinking water and that the running average of atrazine in a system may be higher than suggested by the four samples it takes per year.”

The atrazine manufacturer’s scientists question both the accuracy and the validity of the NRDC’s assertions.

“Syngenta is required by the EPA to conduct a long list of mandatory high-quality studies under rigorous scrutiny by the agency,” says Tim Pastoor, principal scientist for Syngenta Crop Protection, in a statement issued by the company.

“Every data point is available to verify the studies were done properly and the science can be verified by EPA scientists. Recently cited studies by activist organizations are not required to adhere to the same standards. The EPA’s recent evaluation reviewed the best science in its regulatory decision so another review would only repeat work that has already been done.”

But it’s the NRDC’s statement that atrazine should be phased out because it has minimal or no benefits for crop production that may get the greatest amount of push back from Syngenta and farmers alike.

“Evidence of atrazine’s toxic effects on sensitive wildlife species and its potential risk to human health is abundant,” the NRDC says. “The monitoring data show that high contamination levels in the Midwestern and Southern United States are pervasive. There is little compelling evidence that atrazine is needed by farmers.”

The EPA estimates the loss of atrazine would cost corn growers $28 an acre in lost yields and substitute herbicide costs. The total negative impact on corn, sorghum and sugar cane growers in the United States, it says, would exceed $2 billion per year.

For more information on the uses and economic benefits of the product, go to www.atrazine.com.

e-mail: [email protected]