Relative toxicity of herbicide use in the United States 1990 to 2015

Herbicide use is among the most criticized aspects of modern farming operations, especially in response to widespread adoption of genetically-engineered (GE) herbicide-resistant crops. Many previous analyses of herbicide use have relied on flawed metrics in an attempt to evaluate trends in herbicide intensity and toxicity. Here, it is shown that herbicide use intensity has increased over the last 25 years in corn, cotton, rice, and wheat. Although GE glyphosate-resistant crops have been previously blamed for increasing herbicide use, herbicide use increased more rapidly in the non-GE crops rice and wheat. Even as herbicide use has increased, the chronic toxicity hazard associated with herbicide use decreased in 3 out of 6 crops, while acute toxicity hazard decreased in 5 out of 6 crops. In GE glyphosate-resistant crops, glyphosate accounted for 26% of corn, 43% of soybean, and 45% of cotton herbicide applications. However, due to it’s relatively low chronic toxicity, glyphosate contributed only 0.1%, 0.3%, and 3.5% of the chronic toxicity hazard in these same crops, respectively.