title: Combination effects of pyrethroids and neonicotinoids on development and survival of Chironomus riparius.
abstract: Standard ecotoxicological risk assessments are conducted on individual substances, however monitoring of streams in agricultural areas has shown that pesticides are rarely present alone. In fact, brief but intense pulse events such as storm water runoff and spray drift during application subject freshwater environments to complex mixtures of pesticides at high concentrations. This study investigates the potential risks to non-target aquatic organisms exposed to a brief but intense mixture of the neonicotinoid pesticides imidacloprid and thiacloprid and the pyrethroid pesticides deltamethrin and esfenvalerate, compared to single substance exposure. All four of these pesticides have been detected in surface waters at concentrations higher than benchmark values and both classes of pesticides are known to exert adverse effects on non-target aquatic organisms under single substance exposure scenarios. First instar midge larvae of the non-target aquatic organism, Chironomus riparius, were exposed to combinations of these four pesticides at 50% of their LC50 (96 h) values in a 1h pulse. They were then reared to adulthood in uncontaminated conditions and assessed for survival, development time and fecundity. Our results show that the risk of disruption to survival and development of non-target aquatic organisms under this scenario is not negligible on account of the significant increases in mortality of C. riparius found in the majority of the pesticide exposures and the delays in development after pyrethroid exposure. While none of the deleterious effects appear to be amplified by combination of the pesticides, there is some evidence for antagonism. No effects on fecundity by any of the pesticide treatments were observed.
authors.affiliation: Department of Animal Ecology, Uppsala University, Box 256, SE-75105 Uppsala, Sweden. Electronic address: warren.kunce@ebc.uu.se.
authors.forename: Warren
authors.initials: W
authors.lastname: Kunce
authors.affiliation: Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Science, P.O. Box 7050, SE-75007 Uppsala, Sweden.
authors.forename: Sarah
authors.initials: S
authors.lastname: Josefsson
authors.affiliation: Department of Environmental Toxicology, Uppsala University, Box 256, SE-75105, Uppsala, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Örberg
authors.affiliation: Department of Animal Ecology, Uppsala University, Box 256, SE-75105 Uppsala, Sweden.
authors.forename: Frank
authors.initials: F
authors.lastname: Johansson
mesh_terms: D000818:Animals; D002683:Chironomidae / Q000187:drug effects* / Q000254:growth & development*; D004357:Drug Synergism; D054750:Ecotoxicology; D007093:Imidazoles / Q000032:analysis / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D007928:Lethal Dose 50; D000073943:Neonicotinoids; D009570:Nitriles / Q000032:analysis / Q000633:toxicity; D009574:Nitro Compounds / Q000032:analysis / Q000633:toxicity*; D010575:Pesticides / Q000032:analysis / Q000633:toxicity*; D011722:Pyrethrins / Q000032:analysis / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D007093:Imidazoles; D000073943:Neonicotinoids; D009570:Nitriles; D009574:Nitro Compounds; D010575:Pesticides; D011722:Pyrethrins; D014874:Water Pollutants, Chemical; C017180:decamethrin; C082359:imidacloprid; C017690:fenvalerate
keywords: Aquatic invertebrate; Brief exposure; Midge; Mixture toxicity; Pesticide