Wash-off potential of pyrethroids after use of total release fogger products

Pyrethroids are frequently detected in urban wastewater. Even though treatment facilities remove most pyrethroids (> 90 %) in wastewater, residual concentrations can exceed thresholds that are acutely toxic to sensitive aquatic species. Total release foggers (also known as "bug bombs") are widely used by the general public for insect control. It was hypothesized that these products serve as a source of pyrethroids entering the urban wastewater through the deposition of the active ingredients on various surfaces and subsequent transfer from the contaminated surfaces to the waste stream through cleaning activities. Based on experiments conducted in an enclosure, we found that substantial amounts of a pyrethroid (i.e., cypermethrin) were deposited on various surfaces after a total release fogger use. A series of experiments simulating scenarios that would be representative of common residential cleaning activities indicated that the pyrethroid could be transferred from the contaminated surfaces to other adsorptive materials via physical contact (with or without water as a solvent). The pyrethroid was readily extracted from the adsorptive materials (cotton fabric and filter paper) when water was used as a solvent. Adding a small amount of detergent to the water significantly increased the extraction efficiency compared to water alone. These results indicate that insecticides used in total release foggers can contribute to insecticide loading into the wastewater treatment system via several possible routes, such as contact with or cleaning of exposed surfaces and washing contaminated clothing after their use within a structure.