Development of the simulation model InPest for prediction of the indoor behavior of pesticides

The objective was to develop a computer software package (to be registered as InPest) that runs under Microsoft Excel on a personal computer to help i n the risk assessment of indoor-use pesticides for both applicators and ind oor occupants for various methods of application including space spraying, electric vaporizing, broadcast spraying, and residual spraying. For space s praying, the movement of the pesticide in a sprayed room including droplet settlement, permeation into the floor, degradation, transference, and disch arge by ventilation were described as precisely as possible by various phys icochemical equations. The equations thus obtained were then incorporated i nto the Fugacity model (Level IV). When pesticide information regarding molecular weight, vapor pressure, wate r solubility, and octanol/water partition coefficient is available, InPest is able to simulate the time-dependent concentrations of the pesticide in t he air and residual amounts on floor, wall, and ceiling materials under var ious conditions. Simulation data indicate that the predicted behavior of pe sticides fully agrees with the measured data. Based on the predicted concen trations in the air and amounts of residue on the floor, the levels of expo sure to room occupants via inhalation, dermal, or oral intake can be comput ed and compared with the mammalian toxicological data. Thus, InPest is a po werful tool for evaluating the safety of indoor-use pesticides with regard to human health.