Chapter 69 – Chloracetanilides

Publisher Summary This chapter describes the toxicology of chloracetanilide herbicides such as alachlor, acetochlor, butachlor, metolachlor, and propachlor. Eye and skin irritation studies conducted in rabbits showed alachlor to be non-irritating to the eye and slightly irritating to the skin. Alachlor produced skin sensitization in guinea pigs. Acetochlor has been shown to be practically nonirritating to the eyes and skin of rabbits. A dermal sensitization study in guinea pigs was positive. In studies with rabbits, butachlor was practically non-irritating to the skin and moderately irritating to the eye; dermal sensitization was observed in a study with guinea pigs. Metolachlor did not produce eye or skin irritation in rabbits; the material was positive in a dermal sensitization study with guinea pigs. Eye and skin irritation studies conducted in rabbits showed propachlor to be severely irritating to the eye and slightly irritating to the skin. Propachlor produced skin sensitization in guinea pigs. The herbicidal mode of action for chloracentanilides is not totally understood. It is known that this class of herbicides inhibits the biosynthesis of lipids, alcohols, fatty acids, proteins, isoprenoids, and flavonoids. By inhibiting synthesis of various terpenoid precursors, these herbicides appear to interfere with the production of gibberellins.