Environmental Fate and Effects of Dichloroacetamide Herbicide Safeners: “Inert” yet Biologically Active Agrochemical Ingredients

Safeners are included in many commercial herbicide formulations to selectively protect crops from injury induced by active ingredients. Despite their bioactivity, safeners are classified as inert from a regulatory perspective, and as such, safeners have received minimal attention in the peer-reviewed literature regarding their environmental fate and effects. Herein, we review what is known about the uses, physicochemical properties, environmental transformations, and (eco)toxicological effects of dichloroacetamide safeners, which represent one of the most commonly used safener classes (estimated use of >2 × 106 kg/year in the United States). We particularly highlight transformation pathways that may enhance biological activity and/or persistence; for example, limited studies suggest dichloroacetamides can transform via dechlorination into products with increased bioactivity. We also identify several research needs to improve our understanding of the environmental fate and potential risks of this overlooked agrochemical class, which in turn will enhance the efficacy and safety of future herbicide safener formulations.