Pesticide use in the U.S. and policy implications: a focus on herbicides.

This article examines herbicide use in the United States, providing estimates of poundage, land surface covered, distribution, and recent trends based on federal and state figures. Herbicides are by far the most widely used class of pesticide in the US, where 556 million lbs of herbicide active ingredients (AIs) were applied in 1995. Agriculture accounts for the majority of herbicide use, totaling 461 million lbs of AIs in 1995. Over 60% of the poundage of all agricultural herbicides consist of those that are capable of disrupting the endocrine and/or reproductive systems of animals. In addition, at least 17 types of 'inert ingredients,' which can equal 90% or more of a pesticide product, have been identified as having potential endocrine-disrupting effects. Atrazine is the predominant herbicide used according to poundage, with 68-73 million lbs of AIs applied in 1995. However, 2,4-D is the most widespread herbicide, covering 78 million acres for agricultural uses alone. Both of these herbicides are reported endocrine disruptors. Acetolactate synthase (ALS) inhibitors, namely the sulfonylureas and imidazolinones, are one of the fastest growing classes of herbicides. Many of these herbicides are 100 times more toxic to select plant species than their predecessors, so they can be applied at rates approximately 100 times lower. Consequently, they can affect plant species at concentration levels so low that no standard chemical protocol can detect them. Due in part to these more potent herbicides, the poundage of herbicides used in the US has decreased since the mid-1980s; however, the available data suggest that the number of treated acres has not significantly declined. A thorough assessment of potential exposure to herbicides by wildlife and humans is limited due to the inaccessibility of production and usage data.