Neonicotinoid contamination of global surface waters and associated risk to aquatic invertebrates : a review / Christy A. Morrissey, Pierre Mineau, James H. Devries, Francisco Sanchez-Bayo, Matthias Liess, Micheal C. Cavallaro, and Karsten Liber.

Includes bibliographical references (pages 301-303).

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 = 0.13 μg/L (averages) and 0.63 μg/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 24–96 hour LC50 values exceeding 100,000 μg/L (geometric mean N 44,000 μg/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 1 μg/L under acute exposure and 0.1 μg/L
for chronic exposure. Using probabilistic approaches (species sensitivity distributions), we recommend
here that ecological thresholds for neonicotinoid water concentrations need to be below 0.2 μg/L (shortterm
acute) or 0.035 μg/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 0.035 μg/L. Therefore, it
appears that environmentally relevant concentrations of neonicotinoids in surface waters worldwide are
well within the range where both short- and long-termimpacts on aquatic invertebrate species are possible
over broad spatial scales.