Fipronil Insecticide and Soil-Sample Handling Techniques of State Regulatory Agencies

Abstract

The goal of this project was to examine soil-sample handling techniques used by state regulatory agencies that regulate pesticides and their impact on soil-residue levels of the insecticide fipronil and to offer a standardized soil-sampling protocol. In the United States, the pesticide user industry is large for both agricultural and non-agricultural applications. The United States Environmental Protection Agency regulates pesticide use on a federal level, whereas each state has established a “state lead agency” (SLA) that is responsible for state regulation of pesticides. In the absence of mandatory federal protocols for sample collection by SLAs, each state is free to take environmental samples pursuant to administrative or criminal investigations as deemed appropriate. A comparative study of common sampling practices was performed to evaluate the impact of handling methods on results. Soil was treated with fipronil insecticide and placed in two types of storage containers: in opaque bags that block ultraviolet light or in clear glass jars. Soil samples were placed in a commercial freezer, a cooler with commercial ice, and a growth chamber (incubator) that exposed soil samples to heat, humidity, and ultraviolet light. The results of the experiment revealed that within 72 hr, exposure of the soil samples to freezing, humidity, 37.8°C, or commercial ice in a cooler had no statistically significant effect on the level of fipronil residue in the soil samples used in the experiment. However, soil in glass jars placed in the growth chamber and exposed to 51.6 Kj/m2 of ultraviolet light contained significantly less fipronil residue than the standard soil samples.