Pyrethroids as household insecticides: analysis, indoor exposure and persistence

Summary

Natural pyrethrins from insecticidal pyrethrum extract and pyrethroids (e.g. allethrin, tetramethrin, permethrin, cyphenothrin, cypermethrin, cyfluthrin) are active ingredients in insecticidal formulations such as powder, sprays, impregnated paper for electro-evaporators, mosquito coils, and solutions for wood treatment, all mainly intended for indoor use. Some commercial preparations contain also non-pyrethroid insecticides, such as dichlorovos, propoxur, or phoxim, and piperonyl butoxid as synergist. High-resolution gas-chromatography with oncolumn injection and FID and ECD detection is employed for the analysis of these insecticides in commercial formulations, in air during and after indoor application, and as residues on surfaces. The total input of pyrethroids into a large room amounts to 1 to 30 mg. The concentrations of the pyrethrins and pyrethroids in air (2 to 300 μg/m³) and their deposition on surfaces (up to 1000 μg/m²) reveal possible exposure of humans by inhalation (e.g. 30 μg allethrin or 60 μg tetramethrin) or by skin resorption (e.g. 200 μg allethrin and up to 1000 μg tetramethrin). The insecticides deposited on surfaces and some readily formed transformation products persist for 60 h or longer.