() Potential enhanced toxicity of pyrethroid pesticides with environmental levels of piperonyl butoxide.
Amweg, E1, Weston, D1, Lydy, M2, You, J2, 1 University of California, Berkeley, Berkeley, CA, USA2 Southern Illinois University, Carbondale, IL, USA
ABSTRACT- Pyrethroids are increasingly being used in both agricultural and residential consumer applications, and some formulations contain the synergist piperonyl butoxide (PBO), which effectively blocks metabolism of pyrethroids resulting in greatly enhanced toxicity to invertebrate pests. Aquatic sediments from urban and agricultural areas contain pyrethroids in detectable (>1 ppb) and sometimes toxic concentrations. This study was intended to determine if PBO in runoff could be an effective synergist, causing toxicity to non-target invertebrates in aquatic systems where pyrethroid concentrations would otherwise be inconsequential. Ten-day sediment LC50s for permethrin were determined for the freshwater amphipod Hyalella azteca with concurrent exposure to PBO either in the overlying water, or in sediment and water at equilibrium concentrations. The lowest effective PBO concentrations necessary to synergize permethrin toxicity was determined over a range of 0.1 ppb to 60 ppb PBO in water, and 40 ppb to 24,000 ppb PBO in sediment. Environmental concentrations of pyrethroids and PBO from a survey of urban creeks in California and Tennessee and environmental data from the literature are also presented to compare the concentrations at which PBO was an effective pyrethroid synergist in the laboratory with concentrations which are environmentally relevant in urban-dominated water bodies.
Key words: synergism, pyrethroid, piperonyl butoxide, hyalella azteca