Atrazine is a member of the chlorophenoxy-triazine (or triazine) family of herbicides, arguably the most widely used class of agricultural chemicals to date. Development of the triazines began in the early 1950s by J.R. Giegy, Ltd., whose chemists and biologists in Switzerland and the United States launched an ambitious new effort to combat the weeds most plaguing to farmers (LeBaron, et al, 2008, p. 13). At the time, the dominant herbicide in the US was 2,4-D, applied at the rate of over 34 million pounds annually (LeBaron, 2008, p.14). Atrazine was registered for use in Switzerland in 1956 and in the US in 1958, and quickly became the most popular of the triazines for its effectiveness against a wide spectrum of weeds in a range of conditions, including in dry soil. It has since become one of the most widely researched herbicides to date (LeBaron, et al, 2008, p.3).

Eliminating broadleaf weeds with herbicides reduces the need for soil tilling, a practice that contributes to topsoil erosion, a major environmental concern since the Dust Bowl storms of the 1930s. The use of atrazine may boost crop yields by anywhere from 6.5% to less than 1% (Ackerman, 2007, pp. 47-448). And, one study reported that sweet corn treated with a mixed herbicide preparation including atrazine developed more carotenoids, suggesting that atrazine may potentially increase the nutritional value of one of the main crops it is used on (Kopsell, 2009).
 
Today, atrazine remains the most widely used herbicide in the US and in most major agricultural nations outside of the European Union. It is used on cultivated farmland to inhibit the emergence of, and to exterminate, broadleaf weeds, and is applied alone or combined other herbicides. Atrazine is used on over fifty different crops, including corn, which represented nearly 25% of total US crop acreage as of 2000¹ and is a significant export crop of China, Brazil, and Mexico (LeBaron, et al, 2008, p. 4). The United States alone uses an estimated 76 million pounds of atrazine annually, and over 75% of the corn grown in the U.S. is treated with it (EPA FactSheet). Other crops treated with atrazine include citrus, soybean, sorghum, sugarcane, grapes, and forestry products. Though it is by far most heavily used in agricultural regions, atrazine is also used to maintain residential lawns and recreational turf.

(Map created by US Geological Survey.)

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1 US EPA, "Major Crops Grown in the United States", online reference available at: http://www.epa.gov/oecaagct/ag101/cropmajor.html