imidacloprid (ISO); 1-(6-chloropyridin-3-ylmethyl)-N-nitroimidazolidin-2-ylidenamine

Endpoint summary

Description of key information

The substance was tested on different aquatic organisms, representing the three trophic levels: fish, invertebrates and algae; furthermore, testing on microorganisms also is available. With respect to fish, data are available for both freshwater and marine water.

The 96-hour LC50 for fish exposed to the present test material was 211 mg a.s./L for O. mykiss in freshwater and 161 mg a.s./L for C. variegatus in saltwater.

The 48-hour EC50 for aquatic invertebrates exposed to the present test material was 85 mg a.s./L based on Daphnia magna.

The ErC50 greater than 100 mg/L was derived for Pseudokirchneriella subcapitata after 72h exposure, whereas the NOEC was below 100 mg/L.

The NOEC for fish based on early life stages testing with rainbow trout (Oncorhynchus mykiss) was set at 9.02 mg a.s./L.

The 21-day NOEC for aquatic invertebrates exposed to the present test material was the 1.8 mg a.s./L based on Daphnia magna.

The 3-hour EC50 for microorganisms exposed to the present test material was > 1000 mg/L for activated sludge.

Thus, the most sensitive values refer to the invertebrate Daphnia, for both, the acute and the chronic aquatic toxicity.

Additionally, the potential endocrine disrupter effects were assessed for aquatic vertebrates (fish and amphibian). In both studies, the results lead to no potential endocrine disrupting properties.

Additional information

Short-term toxicity studies assessed the effects on fish. Two key studies, according to OECD 203 were performed with rainbow trout (M-006827-01-2; Oncorhynchus mykiss, 96 h, freshwater) and sheepshead minnow (M-007051-01-2; Cyprinodon variegatus, 96 h, saltwater). The lowest acute effect value in fish was determined in C. variegatus with an LC₅₀(96h) of 161 mga.s./L (mean measured).

In an acute toxicity test on the freshwater invertebrate Daphnia magna (M-006821-01-1), immobilisation was assessed, resulting in an EC₅₀(48 h) of 85 mg a.s./L (mean measured). Testing was done according to the EPA OPP 72-2 (Aquatic Invertebrate Acute Toxicity Test).

The toxicity of the substance to algae was investigated in a study performed according to OECD 201 with the freshwater algae Pseudokirchneriella subcapitata reported as Selenastrum capricornutum (M-033262-01-1). The 72-h ErC₅₀was > 100 mg a.s./L (nominal). The NOEC (72 h) was determined to be <100 mg a.s./L (nominal). A supporting study with Desmodesmus subspicatus (M-006854-01-2) resulted in a NOEC (72 h) >10 mg a.s./L (nominal).

 

The long-term effects of the substance towards fish were examined in a flow-through 31-day early-life stage toxicity test with the rainbow trout O. mykiss (M-049894-01-2) according to OECD 210. A NOEC (31d) of 9.02 mg/L (mean measured) was determined as the lowest derived chronic value.

The long-term effects of the substance towards aquatic invertebrates were examined in a 21-day toxicity test with Daphnia magna (M-006824-01-1) according to OECD 211. A NOEC (21d) of 1.8 mg a.s./L (mean measured) was determined.

The effect of the substance on the respiration rate of microorganisms (M-036840-01-1; activated sludge) was examined in a dose-response test at 1000 mg a.s./L.The EC₅₀(3 h) was determined to be > 1000 mg a.s./L (nominal).

 

Additionally, the potential endocrine disrupting effects were assessed for aquatic vertebrates.

A GLP-study dated 2012 is available for the fish (M-428258-01-1). Within this study, a fish short-term reproduction assay was conducted with the test item according to the protocol developed by Ankley et al. (Environ Toxicol Chem 20: 1276-1290, 2001) to assess the reproductive performance of groups of fathead minnows (Pimephales promelas) as the primary indicator for endocrine activity. Additionally, measurements of morphology, histopathology, and biochemical endpoints were performed to further evaluate any toxicological and/or endocrine effects of the test item. This study was conducted according to the OPPTS Guideline 890.1350 (2009). The mature fathead minnows (Pimephales promelas) were exposed under flow through conditions to mean measured concentrations of 0.5, 2.52 and 9.02 mg a.s./L, for 21 days. Since no obvious findings were noticed up to and at the híghest tested concentration of 9.02 mg a.s./L, the NOEC was ≥ 9.02 mg a.s./L. Further, the results provided no evidence for any endocrine disrupting properties.

A GLP-study dated 2012 is available, which was conducted with an amphibian (M-428255-01-1). This study was conducted according to the OPPTS Guideline 890.1100 (2009). For assessment of any endocrine activity, the amphibian metamorphosis is considered. The Xenopus laevis tadpoles were exposed under flow through conditions to mean measured concentrations of 0.73, 3.7 and 18.5 mg a.s./L, alongside with a control, for 21 days. A significant difference in normalized hind limb length after 21 days was reported which however was not considered to be endocrine effect related.