The behaviour of pyrethroids indoors: A model study

Pest control agents containing three different formulations of the pyrethroids permethrin and deltamethrin and/or pyretkrines and the synergist piperonyl butoxide were applied in a model house simulating indoor pest control. The concentrations of the agents were monitored in the gas phase, on suspended particles, house dust and on furniture surfaces over a period of 24 months. Permethrin and deltamethrin were detected only in the gas phase immediately after application of the agents. High concentrations of deltamethrin (similar to 2 mu g/m(3)) and permethrin (similar to 40 mu g/m(3)) were found on suspended particles directly after application. This concentration decreased rapidly within two days (deltamethrin similar to 5 ng/m(3), permethrin similar to 100 ng/m(3)) but much more slowly during the following 24 months. In house dust, deltamethrin was observed with initial concentrations of similar to 50 mg/kg and permethrin at initial concentrations of 150-800 mg/kg (depending on the formulation). The concentration levels of both compounds decreased by a factor of similar to 10 within the first 12 months but remained almost constant thereafter. Decontamination of the rooms using a commercially available household cleanser has little effect on the pyrethyroid concentration found on suspended particles, but leads to a substantial reduction of the contamination level in house dust and on furniture surfaces. (C) Indoor Air (1997).