An Exposure Characterization of a Large Scale Application of a Biological Insecticide,Bacillus Thuringiensis

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Abstract
The gypsy moth, Lymantria dispar, is one of the most destructive insect pests of trees and shrubs in the United States. Since its introduction in the United States in 1869, the gypsy moth has extensively infested areas of 13 northeastern and mid-atlantic states. Smaller, localized infestations have been found in recent years in 17 other states across the nation. When DDT was available, the gypsy moth was almost eradicated from the United States, but as DDT use was curtailed, the gypsy moth infestations became widespread. The State of Oregon has chosen to primarily use the biological insecticide Bacillus thuringiensis var kurstaki (Bt) to eradicate the gypsy moth from approximately 250,000 acres of forested and urban areas in Lane County, Oregon. Personal exposure and area air monitoring for Bt was conducted to determine occupational and general public exposure potential to Bt. Portable sampling pumps with membrane filters (MF) were used to conduct the sampling. Analysis of the MF for Bt involved microbial culture techniques with the presence of toxin crystal formation confirming identification as Bt. This paper presents the exposure sampling results, discusses problems encountered when conducting microbial sampling with membrane filters, and discusses modifications to resolve the problems. Occupational exposure results ranged from 0 to 5600 colony forming units (CFU) of Bt/m3. General public Bt exposure results ranged from 0 to 1600 CFU/m3.

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