Chapter 99 – The Safety Assessment of Piperonyl Butoxide

Publisher Summary This chapter explores the chemistry, formulation, and usage and presents an exposure assessment of piperonyl butoxide (PBO). It is an insecticide synergist produced from the condensation of the sodium salt of 2-(2-butoxyethoxy) ethanol and the chloromethyl derivative of hydrogenated safrole (dihydrosafrole). PBO is usually formulated with natural pyrethrins or synthetic pyrethroids in ratios (PBO: pyrethrins) ranging from 3:1 to 20:1. Formulations of PBO and carbamates are also available, although their use is minor relative to that of PBO and pyrethrins/pyrethroids. It inhibits the mixed function oxidase (MFO) system of insects, thereby reducing the oxidative breakdown of other pesticides such as pyrethrum and the synthetic pyrethroids. PBO enhances the pesticidal activity of a given level of active ingredient, thus promoting reduced use of the pesticide. It is also used extensively in combination with pyrethrins, various synthetic pyrethroids, and other insecticides to control insect pests in and around the home and in food-handling establishments. A wide variety of water-based PBO-containing products such as crack and crevice sprays, total release foggers, and flying insect sprays are made for use by consumers in the home. PBO is generally of low acute toxicity to animals. It is mildly irritating to the eye and skin, but it is not a dermal sensitizer. As a known alternative substrate for the liver microsomal enzyme system, PBO will inhibit the metabolism of many xenobiotics including drugs and pesticides. Rats quickly metabolize single large doses of PBO. Repeated PBO doses will generally induce the metabolism of phenobarbital and other xenobiotics.