Conversion of Pyrethroid Insecticides to 3-Phenoxybenzoic Acid on Urban Hard Surfaces

The urban use of pyrethroids has been associated with the contamination and toxicity of urban surface water. A less considered phenomenon is that many pyrethroids may be transformed to a common intermediate, 3-phenoxybenzoic acid (3-PBA), that is an endocrine-disrupting compound. Here we examined the conversion of five common pyrethroids, permethrin, A-cyhalothrin, deltamethrin, fenpropathrin, and esfenvalerate, to 3-PBA on concrete. Formation of 3-PBA was almost instantaneous, reaching up to 3% of the initial level of pyrethroids within hours of exposure, and was caused mainly by hydrolysis, likely enhanced by the strong alkalinity of concrete. The accumulation of 3-PBA on concrete was transient, with half-lives of 4.2-6.7 h depending on the treatment. Low levels (nanograms per liter) of 3-PBA were frequently found in urban streams draining residential neighborhoods, validating the off-site transport potential of 3-PBA from urban hard surfaces. Findings from this study suggested that urban hardscapes such as concrete pavement are reactive surfaces, conducive to the formation of biologically active transformation products.