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Ecotoxicological information

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Experimental studies are available investigating the short- and long-term effects of the test item on aquatic organisms from three different trophic levels. The studies were performed according to internationally accepted guidelines in accordance with GLP. For all trophic levels freshwater and marine studies are available.
The short-term toxicity fish was investigated using the freshwater fish Oncorhynchus mykiss as well as Pimephales promelas (M-486042-01-1 and M-489576-01-1). Both studies were performed according to OECD 203 as a limit test with a concentration of 10 mg a.i./L. No effects were observed and a LC50 (96 h) of > 10 mg a.i./L (nominal) was derived in both studies. The study with the marine species Cyprinodon variegatus (M-508088-01-1) was performed under comparable conditions to the freshwater study (OECD 203, GLP). The test organism was exposed to two nominal concentrations of 5 and 10 mg a.i./L (nominal). No mortality was recorded and a LC50 (96 h) of > 9.09 mg/L (measured) was derived. In all studies the test substance was shown to be stable by suitable analytical methods.
In order to assess the chronic toxicity of the test item to fish two experimental studies were performed according to OECD 210 (GLP) with the freshwater fish Pimephales promelas (M-565378-01-1) and the marine species Cyprinodon variegatus (M-547597-01-1). Early life stages of P. promelas were exposed under flow-through conditions to 0.313, 0.625, 1.25, 2.50 and 5.00 mg a.i./L. Hatching rates, sub-lethal symptoms, fry survival and growth (length and wet and dry weight) were recorded. After 33 d of exposure (28 d post-hatch) an overall NOEC (33 d) of 2.5 mg a.i./L (nominal) was derived based on total length of fish. Cyprinodon variegatus was exposed to the same test concentrations but was shown to be less sensitive. No effects on any of the examined parameters were recorded. Thus, an overall NOEC (35 d) of ≥ 4.21 mg a.i./L (mean measured concentrations) was derived.
The short-term toxicity to aquatic invertebrates was assessed in four experimental studies. Two were performed with the freshwater organism Daphnia magna (M-566522-02-1, M-502273-01-1). Two of the available studies were performed with the marine species Crassostrea virginica (M-507732-01-1) and Americamysis bahia (M-503278-01-1). The studies with Daphnia magna were performed according to OECD 202 (GLP). In the key study D. magna was exposed to five nominal concentrations of 41.9, 71.2, 121, 206 and 350 μg a.i./L under static conditions. The mobility of D. magna was affected and an EC50 (48 h) of 173.3 µg/L (nominal) was calculated. The supporting study (M-502273-01-1) resulted in an EC50 (48 h) of 247 µg a.i./L (nominal).

The key study with the marine species Crassostrea virginica investigated the effects of the test item on shell deposition for 96 h. It was performed according to EPA OPPTS 850.1025 (GLP) and the shells were exposed to 0.31, 0.65, 1.3, 2.5 and 5.0 mg a.i./L (nominal). After 96 h an EC50 of 2.2 mg a.i./L (nominal) was calculated. A. bahia was shown to be less sensitive to the test item. The mortality was recorded for 96 h and a LC50 (96 h) of 8.3 mg a.i./L (measured) resulted. In conclusion, marine invertebrates were less sensitive to the test item compared to freshwater organisms.
The same trend was observed in the chronic studies with aquatic invertebrates (M-538451-01-1 and M-508258-01-1). In a long-term study with Daphnia magna according to OECD 211 (GLP) the test species were exposed to concentrations up to 140 µg/L under semi-static conditions. The reproduction of Daphnids was inhibited and a NOEC (21 d) and EC10 (21 d) of 13.3 µg a.i./L and 28.0 µg a.i./L were calculated, respectively. In the study with the marine species A. bahia which was performed according to EPA OPPTS 850.1350 (GLP) a NOEC (30 d) of 0.15 mg a.i./L (measured) was reported based on reproduction.
The toxicity to aquatic algae was investigated in three experimental studies (M-535793-01-1, M-553842-02-1 and M-527594-01-1). Two studies were performed with freshwater organisms whereas one was performed with a marine diatom species. The key study with the freshwater species Navicula pelliculosa was performed according to OECD 201 (GLP). N. pelliculosa was exposed to five nominal concentrations up to 5 mg a.i./L under static conditions for up to 96 h. The growth was slightly inhibited allowing the derivation of a NOEC (72 h) of 0.285 mg a.i./L (measured geom. mean). In the supporting study with Pseudokirchneriella subcapitata which was performed according to OECD 201 (GLP), no effects on growth of algae cells were recorded up to the highest concentration tested. A NOEC (72 h) of ≥ 1.97 mg a.i./L and an EC50 (72 h) of > 1.97 mg a.i./L were derived based on the geometric mean measured concentrations. The study with the marine species Skeletonema costatum was performed according to OECD 201 (GLP). Inhibition of growth was measured and an EC50 (72 h) of 1.49 mg a.i./L and a NOEC (72 h) of 0.429 mg a.i./L were calculated.
The toxicity of the test item to aquatic plants was studied in a GLP guideline study according to OECD 221 with Lemna minor (M-532733-02-1). Duckweed were exposed to nominal concentrations up to 10 mg a.i./L. Total frond area as well as total frond number were investigated for 7 d in a semi-static test system. After 7 d an EC50 > 6.64 mg a.i./L (measured, time weighted average) and a NOEC of 2.05 mg a.i./L (measured, time weighted average) were derived.
In conclusion aquatic invertebrates were the most sensitive taxonomic group in acute and chronic studies with freshwater organisms. For marine organisms aquatic invertebrates were most sensitive in chronic studies whereas marine diatoms were slightly more sensitive in the acute studies.

The toxicity to the microbial community was studied in a GLP guideline study according to OECD Guideline 209 and EU Methode C.11 (M-585194-01-1). The activated sludge was exposed to the test item at a limit test item concentration of 100 mg/L without ATU (N-allylthiourea) representing the total microbial community and with ATU representing the heterotrophic part of the microbial community. The respiration rate of each mixture was determined after aeration periods of 3 hours. The test item showed 2.1% respiration inhibition of activated sludge at a test item concentration of 100 mg/L. The EC50 (3 h) is higher than 100 mg/L. The NOEC (3 h) is equal or higher than 100 mg/L. Thus, it can be concluded that the degradation process in sewage treatment plants is not inhibited by the test item.