Washington, DC–(ENEWSPF)–November 23, 2015. Commonly-used pesticides can impact aquatic species over multiple weeks, even when chemicals are no longer detectable in water nor monitored by regulators, according to new research. The study, titled A long-term assessment of pesticide mixture effects on aquatic invertebrate communities, published in the journal Environmental Toxicology and Chemistry, investigates the long-term effects on aquatic invertebrate communities of commonly-used insecticides: two pyrethroids (permethrin and lambda-cyhalothrin) and an organophosphate (chlorpyrifos). Pesticide applications were based on environmentally relevant concentrations and lethal concentrations (a concentration required to kill a certain percentage of animals tested) ranging from 10% (LC10) to 50% (LC50). Researchers made repeat applications in order to mimic runoff events in a multiple grower or homeowner watershed. The results indicate that insecticide mixtures continue to impact natural systems over multiple weeks, even when bound to particles and no longer detectable in water. Combinations of indirect and direct effects caused consequences across the food chain. Pyrethroids rapidly dissipated from the water column, whereas chlorpyrifos was detectable even six weeks after application.
