Comparison of ecological risks of insecticides for nursery-box application using species sensitivity distribution

Abstract

e ecological risks to aquatic organisms posed by insecticide use were compared using species sensitivity distribution (SSD) to determine if nursery-box application is ecologically safer than surface-water application. e targeted insecticides were imidacloprid and pronil for nursery-box application and fenitrothion as a reference for surface-water application. Ecological risks were quanti ed as the potentially a ected fraction (PAF) of species calculated using SSD and the pesticide concentration in river and paddy water. e PAF value was the highest for fenitrothion in both river and paddy water, indicating that substituting nursery-box for surface-water application reduces the ecological risk. e validity of our SSD approach for risk quanti cation was con rmed with comparisons in mesocosm studies. e comparisons suggest that the PAF values successfully correspond to the magnitude of the pesticide e ect on ecosystems. e actual ecosystem appeared to have strong recovery potential, even when more than 50% of the species were a ected. © Pesticide Science Society of Japan Keywords: risk assessment, imidacloprid, pronil, potentially a ected fraction. Electronic supplementary materiale online version of this article contains supplementary material (Supplemental Tables S1 and S2), which is available at http://www.jstage.jst.go.jp/browse/jpestics/. IntroductionIn Japan, pesticide registration criteria based on ecological risk assessment are set by the Japan's Ministry of Environment under the Pesticide Regulation Law.1) Under the risk assessment scheme, acute toxicity tests are conducted for sh (Cyprinus carpio), daphnids (Daphnia magna), and algae (Pseudokirchneriella subcapitata), and then the acute e ect concentration (AEC) is determined as the minimum value of the 50% e ect concentration (EC 50 ) or 50% lethal concentration (LC 50 ) divided by an uncertainty factor (10 for sh and crustaceans and 1 for algae). Subsequently, the predicted environmental concentration (PEC), which is the peak concentration in river water at the time of pesticide application, is calculated using an environmental model based on a standard scenario in a model basin.2) Finally, if the PEC is less than the AEC, the short-term aquatic risk is deemed to be insigni cant and the pesticide is considered to ful ll the criteria.Various measures are taken by farmers for the protection of biodiversity, such as reducing pesticide use, substituting to safer pesticides, and preventing of pesticide runo into river water.However, the e ciency of the risk management options has not been evaluated. e present risk assessment scheme is deterministic, and therefore does not allow the comparison of risks under the various risk management options. Insecticide application in rice paddy elds in Japan has gradually shi ed from surfacewater application to nursery-box application in light of its many advantages such as reduced labor, long-term e ect, and low runo and dri . However it is necessary to determine if nurserybox application is ecologically safer than surface-w...

Ecological effect assessment by species sensitivity distribution for 68 pesticides used in Japanese paddy fields

“…Semi-field experiments (microcosm/mesocosm) have provided more realistic ecological effects of pesticides than single-species toxicity experiments in the laboratory. Several studies [9][10][11][12][13] showed that the values of HC 5 based on acute toxicity were protective against adverse ecological effects under single short-term exposure in freshwater microcosm/mesocosm experiments. Their results indicate the validity of HC 5 values as predicted no-effect concentrations in aquatic ecosystems.…”

“…SSD has also been used for quantitative ecological risk assessment of pesticides, such as diazinon 14) and aldicarb 15) insecticides, atrazine herbicide, 16) and pesticide mixtures. 17) Our previous studies 9,18,19) also conducted probabilistic ecological risk assessment of several paddy insecticides and herbicides. The potentially affected fraction (PAF) is an index of the magnitude of ecological risk (Fig.…”

Studies on ecological risk assessment of pesticide using species sensitivity distribution

“…2). 4) If the environmental concentration is just below the registration criteria (8500 µg/L), most arthropod species would be affected. Daphnia magna, which is generally sensitive to insecticides and therefore is regarded as the standard species for toxicity testing of arthropods, is not always sensitive, especially to neonicotinoids.…”

“…[7][8][9] Semi-field experiments (microcosm/mesocosm) have provided more realistic ecological effects of pesticides than single-species toxicity experiments in the laboratory. Several studies 4,[10][11][12][13] have shown that the HC 5 values based on acute toxicity were protective against adverse ecological effects with single short-term exposure in freshwater microcosm/mesocosm experiments. Their results indicate the validity of HC 5 values as predicted no-effect concentrations in aquatic ecosystems.…”

“…4). 4,10) The toxicity data for herbicides were separated into primary producers and other species because primary producers are the most sensitive taxonomic group to herbicides, and the SSD showed a clear separation of primary producers from others ( Fig. 4).…”