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 5 0 h after broadcast treatment for flea control in residences. Insectic ide formulation, time after treatment, ventilation regime, and height above floor affected airborne residues. Before spraying chlorpyrifos r esidues were low or undetected. In nonventilated residences, chlorpyri fos residues peaked in 0-6 h after treatment at 38 ng/liter for emulsi fiable, remained low at <12 ng/liter for the microencapsulated, and sh arply peaked in 1-2 h after treatment at 52 ng/liter for the aerosol f ormulation. Residues for all formulations then slowly declined through 50 h. In ventilated residences, chlorpyrifos residues peaked from 2 t o 10 h after treatment at 25-27 ng/liter for emulsifiable, remained lo w at <10 ng/liter, and sharply peaked in 0-2 h after treatment at 21 n g/liter far the aerosol formulation. Maximum airborne concentrations m ere 74 ng/liter for emulsifiable, 17 ng/liter for microencapsulated, a nd 61 ng/liter for aerosol chlorpyrifos.