Chlorpyrifos formulation effect on airborne residues following broadcast application for cat flea (Siphonaptera: Pulicidae) control.

Airborne residues of 3 chlorpyrifos formulations were measured up to 50 h after broadcast treatment for flea control in residences. Insecticide formulation, time after treatment, ventilation regime, and height above floor affected airborne residues. Before spraying, chlorpyrifos residues were low or undetected. In nonventilated residences, chlorpyrifos residues peaked in 0-6 h after treatment at 38 ng/liter for emulsifiable, remained low at < 12 ng/liter for the microencapsulated, and sharply peaked in 1-2 h after treatment at 52 ng/liter for the aerosol formulation. Residues for all formulations then slowly declined through 50 h. In ventilated residences, chlorpyrifos residues peaked from 2 to 10 h after treatment at 25-27 ng/liter for emulsifiable, remained low at < 10 ng/liter, and sharply peaked in 0-2 h after treatment at 21 ng/liter for the aerosol formulation. Maximum airborne concentrations were 74 ng/liter for emulsifiable, 17 ng/liter for microencapsulated, and 61 ng/liter for aerosol chlorpyrifos.