title: Neonicotinoid contamination of global surface waters and associated risk to aquatic invertebrates: a review.
abstract: Neonicotinoids, broad-spectrum systemic insecticides, are the fastest growing class of insecticides worldwide and are now registered for use on hundreds of field crops in over 120 different countries. The environmental profile of this class of pesticides indicate that they are persistent, have high leaching and runoff potential, and are highly toxic to a wide range of invertebrates. Therefore, neonicotinoids represent a significant risk to surface waters and the diverse aquatic and terrestrial fauna that these ecosystems support. This review synthesizes the current state of knowledge on the reported concentrations of neonicotinoids in surface waters from 29 studies in 9 countries world-wide in tandem with published data on their acute and chronic toxicity to 49 species of aquatic insects and crustaceans spanning 12 invertebrate orders. Strong evidence exists that water-borne neonicotinoid exposures are frequent, long-term and at levels (geometric means=0.13μg/L (averages) and 0.63μg/L (maxima)) which commonly exceed several existing water quality guidelines. Imidacloprid is by far the most widely studied neonicotinoid (66% of the 214 toxicity tests reviewed) with differences in sensitivity among aquatic invertebrate species ranging several orders of magnitude; other neonicotinoids display analogous modes of action and similar toxicities, although comparative data are limited. Of the species evaluated, insects belonging to the orders Ephemeroptera, Trichoptera and Diptera appear to be the most sensitive, while those of Crustacea (although not universally so) are less sensitive. In particular, the standard test species Daphnia magna appears to be very tolerant, with 24-96hour LC50 values exceeding 100,000μg/L (geometric mean>44,000μg/L), which is at least 2-3 orders of magnitude higher than the geometric mean of all other invertebrate species tested. Overall, neonicotinoids can exert adverse effects on survival, growth, emergence, mobility, and behavior of many sensitive aquatic invertebrate taxa at concentrations at or below 1μg/L under acute exposure and 0.1μg/L for chronic exposure. Using probabilistic approaches (species sensitivity distributions), we recommend here that ecological thresholds for neonicotinoid water concentrations need to be below 0.2μg/L (short-term acute) or 0.035μg/L (long-term chronic) to avoid lasting effects on aquatic invertebrate communities. The application of safety factors may still be warranted considering potential issues of slow recovery, additive or synergistic effects and multiple stressors that can occur in the field. Our analysis revealed that 81% (22/27) and 74% (14/19) of global surface water studies reporting maximum and average individual neonicotinoid concentrations respectively, exceeded these thresholds of 0.2 and 0.035μg/L. Therefore, it appears that environmentally relevant concentrations of neonicotinoids in surface waters worldwide are well within the range where both short- and long-term impacts on aquatic invertebrate species are possible over broad spatial scales.
authors.affiliation: Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan, Canada; School of Environment and Sustainability, 117 Science Place, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. Electronic address: christy.morrissey@usask.ca.
authors.forename: Christy A
authors.initials: CA
authors.lastname: Morrissey
authors.affiliation: Pierre Mineau Consulting, 124 Creekside Dr., Salt Spring Island, BC V8K 2E4, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Mineau
authors.affiliation: Institute for Wetland and Waterfowl Research, Ducks Unlimited Canada, P.O. Box 1160, Stonewall, Manitoba, Canada.
authors.forename: James H
authors.initials: JH
authors.lastname: Devries
authors.affiliation: Faculty of Agriculture & Environment, University of Sydney, NSW 2015, Australia.
authors.forename: Francisco
authors.initials: F
authors.lastname: Sanchez-Bayo
authors.affiliation: UFZ, Helmholtz Centre for Environmental Research, Department System-Ecotoxicology, Permoserstrasse 15, 04318 Leipzig, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Liess
authors.affiliation: School of Environment and Sustainability, 117 Science Place, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Cavallaro
authors.affiliation: School of Environment and Sustainability, 117 Science Place, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan, Canada.
authors.forename: Karsten
authors.initials: K
authors.lastname: Liber
mesh_terms: D000818:Animals; D006146:Guanidines / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D007093:Imidazoles / Q000032:analysis; D007306:Insecticides / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D007448:Invertebrates / Q000187:drug effects*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000032:analysis; D012306:Risk; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D060753:Water Quality
chemical_list: D006146:Guanidines; D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D014874:Water Pollutants, Chemical; C082359:imidacloprid
keywords: Aquatic invertebrates; Neonicotinoids; Pesticides; Risk assessment; Species sensitivity distribution; Water quality guidelines