2,4-Dichlorophenoxyacetic acid (2,4-D) and its chemical derivatives are widely used herbicides. A large number of formulations are available containing different 2,4-D salts (sodium, amine, alkylamine, and alkanolamine) and esters (propanoic acid, butanoic acid, and other alkoxy compounds). The most frequently used agricultural product, based upon 2013 California pesticide use data, is the dimethylamine salt of 2,4-D. Current California registration data (November 2015) show 205 formulations for the dimethylamine salt, with concentrations ranging from 0.12% (for the most dilute home use product) to 46.8–96.9% (for agricultural formulations). Although some concentrated formulations of 2,4-D esters are wettable powders, others contain petroleum solvents (identified on the "first aid" statement on the pesticide label); even though these solvents are considered "inert" ingredients because they are not pesticides, they may have their own innate toxicity (see "Toluene and Xylene" and "Hydrocarbons").
Agent Orange was a mixture of the chlorophenoxy herbicides 2,4-D (dichlorophenoxyacetic acid) and 2,4,5-T (trichlorophenoxyacetic acid) that also contained small amounts of the highly toxic contaminant TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin, derived from the process of manufacturing 2,4,5-T. Manufacture of 2,4-D by chlorination of phenol does not produce TCDD. Populations involved in the manufacture or handling of 2,4,5-T may show elevated levels of TCDD on serum testing and overall increased rates of cancer compared with the general population.