Pesticide inhalation exposure, air concentration, and droplet size spectra from greenhouse fogging

ABSTRACT. Fogger application of pesticide in greenhouses can reduce application time and applicator contact with equipment. Since fog applications use smaller and more concentrated droplets than typical wet spray applications, potential for inhalation and off-target transport hazards may be increased. This study investigated temporal characteristics of airborne pesticide after thermal fogging of a greenhouse. Droplet size spectra and concentration of airborne pesticide were measured. Volume median diameter of the suspended aerosol decreased from 14 to 2.3 µm during 1.5 h after application. Concentration of airborne pesticide decreased by 60% in the first hour after application and by 95 % during 12 h after application. Implications for respiratory exposure were analytically developed from observed data. Hand spraying with high-pressure, high-volume systems is the most common technique of pesticide application in greenhouse culture. However, fog or aerosol applications are feasible and often-used alternatives for enclosed structures. The motivations for fog application are the potential to increase spray deposition; improve pest control efficacy; and reduce application times, rates of active ingredients, and applicator exposure. A common fogging procedure in greenhouse operations is to apply the fog in late afternoon or early evening. This practice allow