Nonprofit, nonpartisan journalism. Supported by readers.


As EPA re-evaluates safety of herbicide atrazine, Minnesota conducts its own review

The Environmental Protection Agency reauthorized the use of atrazine three years ago; now a new administration will re-evaluate its safety. Meanwhile, Minnesota prepares to release the results of a yearlong state study.

REUTERS/John Sommers II
Atrazine is heavily used in corn production throughout the Midwest.

It’s been only three years since the U.S. Environmental Protection Agency, (EPA) after one of the most exhaustive scientific investigations of a commercial product ever undertaken, reauthorized use of the herbicide atrazine, the longtime weed-killing staple of corn growers everywhere. Now, nine months into a new administration that has promised a renewed commitment to science and greater transparency on environmental issues, the EPA says it will re-evaluate atrazine yet again.
The agency’s Oct. 7 announcement came just weeks ahead of the expected release of a separate, yearlong study of atrazine done jointly by the Minnesota Department of Agriculture, the state’s Department of Health, and the Minnesota Pollution Control Agency. Gregg Regimbal, supervisor of the Pesticide Management Unit in the state’s Agriculture Department — which, along with the EPA, has regulatory authority over restricted-use farm chemicals in the state — said it would be premature to speculate on whether atrazine use in Minnesota will be modified as a result of the study, but that the review has been “worthwhile.”

‘The toughest one’
Minnesota decided to take a new look at atrazine after a legislative auditor’s report suggested periodic re-evaluations of pesticides should be routine. Regimbal said atrazine was picked first because of ongoing concerns about the product and because “we knew it would be the toughest one coming out of the chute.” The Minnesota review is not an attempt to duplicate anything the EPA does, Regimbal said, and is intended only to “look at the specific conditions of atrazine use” in the state.
“Atrazine is controversial,” said Regimbal. “We understand that. We’re sensitive to that. But we want to do our job. We want to look at the science and make decisions based on the best information.”
The Minnesota findings should be made public around Halloween — perfect timing for a pesticide with a regulatory history that has been a witches’ brew of stalemate and controversy for decades.
Kills weeds but not crops
Atrazine was among the first of the “selective” herbicides that kill weeds but not crops. Used on several crops, it has been especially important in corn production. Atrazine is made by Syngenta, a Swiss chemical company with extensive U.S. operations and which has primary responsibility for maintaining the herbicide’s registration with the EPA. Atrazine was first licensed in the United States in 1958, and for many years was the most heavily used pesticide in the world. It has also been one of the most frequently detected contaminants of water. Atrazine and its breakdown compounds have been found in lakes, streams, reservoirs, clouds, rain, snow, fog, and in water ready for human consumption from drinking-water systems in agricultural areas.
New, ultrasensitive testing methods are now picking up traces of atrazine even in places remote from where it is applied, including lakes in Minnesota’s far north. Although atrazine breaks down quickly when exposed to air, it persists in groundwater, and the potential for aquifer contamination led the European Union to ban atrazine use in 2003. That same year the EPA found widespread atrazine contamination of community well-water in 21 states in the U.S.
Although it is being steadily replaced in corn growing regions by glyphosate — commonly known by the brand name Roundup — atrazine is still a robust seller in Minnesota. In 2008, Minnesota farmers bought more than 3 million pounds of atrazine-based weed-control products.

Atrazine – herbicides

Estimated annual agricultural use (2007)

But corn farmers’ devotion to atrazine has long been accompanied by questions about its safety — and by a protracted review of those concerns by the EPA. In 1988, Congress directed the EPA to reregister atrazine, along with nearly 900 other older pesticides that had never been subjected to modern safety testing. EPA upped the urgency of this process by designating atrazine for “special review” in 1994 after preliminary data suggested it might cause cancer. Over the next 12 years, while the herbicide remained in use, the agency generated more than a million pages of documents on atrazine, and in 2006 formally relicensed it, declaring atrazine not “likely” to be carcinogenic and safe when properly used. The decision came after a late scramble to assess studies showing that atrazine exposure can turn male frogs into hermaphrodites.
Bad press and a damning report
The new EPA review follows media accounts of inadequate monitoring and regulation of community water systems and a damning report by the Natural Resources Defense Council (NDRC) last August that accused the agency of ignoring atrazine contamination in drinking water and in natural watersheds across the Midwest. The NRDC, which has waged a long battle with the EPA over atrazine, has previously sued the agency under provisions of several federal laws the group claims should have long ago led to a ban on atrazine use.
Under an agreement with Syngenta, drinking-water systems and streams shown to contain atrazine are regularly checked to ensure contamination levels stay below concentrations considered unsafe. To date, no community water systems in Minnesota have required monitoring, but the North Fork of the Whitewater River in the southeast part of the state — in the heart of cherished trout fishing country — is under such surveillance. In 2005 and 2006, the river was checked for atrazine more than 100 times, and came up positive in nearly half the samples.
For drinking water, the established safe level of atrazine is an annual average of 3 parts per billion (ppb). But much higher exposures are permitted for shorter periods. The maximum average permitted over a 90-day period is 37.5 ppb, and for a single day it goes up to 298 ppb. Syngenta is required to conduct weekly testing during the growing season of any drinking-water system with annual atrazine levels above 2.6 ppb.
Company considers standards ‘completely protective’
In an email, Syngenta spokesperson Sherry Ford said the company stands firmly behind the safety of atrazine, which she notes has been thoroughly reviewed by agencies in the United States and in other countries. Syngenta considers the current EPA standards for atrazine conservative and “completely protective” of human health, including that of infants, children and pregnant women. The company also remains convinced of the adequacy of its water-monitoring program, which Ford said in the six years since it was implemented has never found annual average concentrations of atrazine in drinking water above the EPA’s annual 3 ppb limit.
But the efficacy of the EPA’s water-monitoring requirements have come into question in new epidemiological studies linking pesticides in drinking water with low birth weights and other developmental problems in babies born in areas of high atrazine use.
Steve Bradbury, deputy director in the Office of Pesticide Programs at the EPA, said the monitoring program has never found atrazine levels approaching the 90-day or one-day maximums. But Bradbury conceded that the new atrazine review is in part a response to complaints that weekly monitoring is insufficient to catch “spikes” of contamination that can occur over short periods when pesticides are applied and immediately after heavy rains that can flush atrazine into water supplies. “We’re going to ask our scientific advisory panel if weekly sampling is sufficient,” said Bradbury.
EPA scientific advisory panels are groups of independent scientists brought in to review the agency’s handling of complex issues. Beginning next month, the EPA will convene the first of four advisory panels that will review the agency’s work on atrazine over the course of the coming year. The panels will be asked to evaluate the EPA’s conclusions about atrazine and human health, including cancer, as well as the agency’s reassessment of water monitoring protocols.
Effects on frogs
The panels will also consider the agency’s earlier findings on atrazine’s effects on frogs, which were contentious. The agency did not act on its own previous advisory panel’s warning that the majority of studies it looked at showed harmful effects of atrazine on amphibian reproductive organs. Instead, the EPA asked Syngenta to carry out further studies on frogs. Those follow-up tests came back negative and the agency considered the issue closed. But just last month, in a massive report reviewing the existing science for the journal Environmental Health Perspectives, researchers reported that eight out of 10 studies show “strong trends or statistically significant alterations” in the reproductive systems of male frogs exposed to atrazine.
One question sure to come before an advisory panel — but unmentioned in EPA’s announcement of the review — is whether atrazine is an endocrine disruptor. Endocrine disruptors are chemicals that mimic hormones or otherwise interfere with normal hormone function. This can have serious developmental and health consequences. And because hormones operate at extremely low concentrations, even tiny doses of an endocrine disruptor can have an effect. The amount of atrazine reported to turn frogs into hermaphrodites, for example, was only .1 ppb — 30 times less than the amount allowed in drinking water.
As it happens, the EPA already knows that atrazine is an endocrine disruptor. In 1996, Congress ordered the agency to develop methods for testing chemicals for endocrine disrupting properties. Progress was slow — endocrine disruption is a new species of toxicology and at times there wasn’t even agreement on a definition of endocrine disruption — but the agency has now completed work on 11 new assays and just this fall finalized a list of more than 60 compounds it plans to begin testing.
To validate the new assays — that is, to make sure they work — it was necessary to find chemicals that produced positive results when tested. One of the chemicals that came up positive was atrazine. In both male and female rats, atrazine was shown to inhibit normal reproductive-system development. Although the mechanism behind this effect isn’t yet completely understood, the agency’s 2007 report on its new assays stated “The conclusion from this study … clearly identified atrazine as interacting with the endocrine system …”
A changing EPA
If history is an indication, the EPA’s latest review of atrazine may be only the first step in a lengthening process extending far into the future. But the agency’s Steve Bradbury said things are changing inside the EPA. During the Bush administration, science often finished second behind ideology on issues like climate change, or air- and water-quality regulation. Bradbury said that the new administration is now insisting that the EPA “stay on top of the science.” The federal laws governing the agency give it broad discretion to end the use of any pesticide it deems dangerous — and at any time. At least in theory, that means the EPA could curtail or even ban atrazine use if at some point in the review process evidence emerges to justify such an action. “The statutes give us the ability to suspend a pesticide if it poses an imminent threat,” said Bradbury. “Imminent threat is a pretty high threshold. But we’re not prejudging what the results of our review will be.”
Jennifer Sass, a staff scientist at NRDC and a co-author of its latest report on atrazine-contaminated water, says the EPA’s willingness to re-evaluate atrazine again is a hopeful sign — but not a guarantee that it will lead to the phase-out of atrazine the NRDC has called for. “The science will get you only so far,” said Sass. “After that the agency has to follow its statutory authority. If they do, then we’re going to see action on atrazine.”
The word “action” does not fit comfortably into a regulatory process that has proceeded at a crawl for more than 20 years. Syngenta, which has invested millions of dollars defending atrazine — while continuing to earn many millions more selling it — could be forgiven for wondering when enough is enough. If there are legitimate questions about atrazine, there are likewise legitimate questions about the EPA’s ability to get it right after so much time and effort. But Steve Bradbury sees atrazine’s never-ending review as just the deliberate nature of the beast.

“This is sort of the beauty of democracy,” said Bradbury. “It is what it is.”

Local journalist William Souder reported on the EPA’s regulation of atrazine for Harper’s magazine in August 2006.

Editor’s Note: Since this story was originally posted, the Minnesota Department of Agriculture and its partner agencies have determined that results of the state’s atrazine study will likely not be finalized until sometime in December.