UC Riverside

In highly urbanized areas, intensive use of pyrethroids has led to offsite transport to surface waters at concentrations known to cause toxicity to aquatic organisms. However, there is limited knowledge on the occurrence and distribution of pyrethroids in urban settings, or the role dust particles play in offsite transport of pyrethroids. Additionally, when pyrethroids enter the environment, they undergo transformation to form a common degradation product 3-phenoxybenzoic acid (3-PBA), which has been shown to cause endocrine disruption. However, little research has been conducted on the formation of 3-PBA in urban environments, its occurrence in urban streams, or its stability in different environmental matrices. Here we first evaluated the occurrence of particle-borne insecticides including pyrethroids in outdoor urban dust and studied their spatial and temporal distribution patterns and correlation with particle sizes. Temporally, particle-bound insecticides increased over the dry season and then significantly decreased after winter rains. Spatially, levels of pyrethroids in dust did not differ with distance from point of application, suggesting redistribution. Pyrethroids were found to associate predominantly with the smallest particle size fraction in dust. These findings suggest that loose particles are likely a significant source for offsite contamination of insecticides. In a subsequent study, we investigated pyrethroid transformation processes on concrete and 3-PBA formation. Pyrethroid degradation was rapid with hydrolysis being the most significant pathway, leading to rapid formation of 3-PBA. Low levels of 3-PBA were constantly detected in urban surface water, suggesting the need to understand chronic exposure and risk to aquatic species. In order to aid risk assessment of 3-PBA, in the last study we examined its stability in different environmental matrices. The half-life of 3-PBA in surface water and aerobic sediments was relatively short, while it was prolonged in soil and anaerobic sediments. These results further suggested that urban soil may be a source of 3-PBA to surface water or underlying groundwater, and due to the continuous input, additional research is needed to evaluate adverse effects on non-target organisms.