In 2003 the U.S. Environmental Protection Agency began requiring that atrazine manufacturers increase monitoring of selected surface water supplies. Although atrazine is highly water soluble, EPA monitoring data found that atrazine is not contaminating groundwater significantly. The problem is that atrazine is showing up in higher-than-expected concentrations in surface water, such as reservoirs, ponds and lakes.

In response, the EPA has ordered atrazine manufacturers to develop a comprehensive monitoring program for community water systems with high atrazine levels. Chemical companies that do not participate cannot continue to market atrazine.

The upshot? "Producers who use weed control products with the active ingredient atrazine need to be extra careful when applying the herbicide to cropfields near watersheds," says Bill Johnson, a Purdue University Extension weed scientist.

"Atrazine in corn is like Roundup in soybeans," Johnson says. "It's easily the number-one herbicide used in corn. It's used on over 80 percent of the acres. The reason it's used is because it's cheap, it's effective and it controls more weeds per dollar spent on herbicide than any other herbicide that we have in corn."

Frog scare
Concern for atrazine in water supplies peaked in 2002 when researchers at University of California-Berkeley, found that frogs living in very low concentrations of the herbicide (0.2 parts per billion in water) tended to be much more likely to have reproductive anomalies where male frogs developed female characteristics. A few studies at other universities succeeded in finding similar endocrine disrupter effects in frogs, raising concerns that the chemical might disrupt human endocrine systems as well.

Such research results have been vigorously refuted by crop protection companies, which have set about burying the frog-unfriendly results with mountains of contrary data that vindicate the chemical. To date, atrazine in drinking water has not been proven to cause deleterious health effects in humans. Contrary research has put its effect on frogs in doubt as well. Nevertheless, the EPA has set a maximum annual average for atrazine in public drinking water of 3 parts per billion (ppb).

Already, Johnson points out that higher concentrations of atrazine have been found in almost a dozen Indiana watersheds. He urges farmers to reduce the risk of atrazine runoff by not making applications nearer to water sources than recommended or at times when the herbicide is more likely to wash away.

No matter how safe atrazine proves to be, a worried, voting public is never going to like the idea of herbicides getting into its lakes and streams. The fact that 3 ppb is an unfathomably low concentration is irrelevant in the political arena. Farmers simply need to use atrazine carefully and keep it out of the water if they want to keep this cheap herbicide around for much longer.

For further information:

Frogs feminized by atrazine?
http://www.sciencenews.org/articles/20020420/fob1.asp

http://outreach.missouri.edu/hesnutrnews/safe4-18-02(2).htm

Syngenta Crop Protection's case for atrazine safety
http://www.syngentacropprotection-us.com/prod/herbicide/Atrazine/index.asp?nav=FSheet2

Atrazine stewardship:

Purdue Weed Science
http://www.btny.purdue.edu/weedscience/

Office of the Indiana State Chemist
http://www.isco.purdue.edu/