Ammonium 2-amino-4-(hydroxymethylphosphinyl)butyrate

Short-term toxicity to aquatic invertebrates

Description of key information

EC50 (48 h) 7.5 mg a.s./L (nominal) (Americamysis bahia) (Forbis, 1986)

Additional information

Four studies on the acute toxicity of glufosinate-ammonium to aquatic invertebrates are available. All studies, with the exception of Fischer (1982), were conducted according to GLP and different international guidelines. One freshwater species (Daphnia magna) and one saltwater species (Americamysis bahia) were tested. The study conducted by Ruhland (2009a) yielded the lowest relevant endpoint for the standard species Daphnia magna and was chosen as key.

The acute toxicity of technical grade glufosinate-ammonium (GA, AE F039866, purity 50.4%) to Daphnia magna was tested under static conditions, when exposed to a limit concentration of 100 mg a. s. /L, corresponding to 198 mg glufosinate-ammonium (tech.) /L (Ruhland, 2009a). The study followed OECD guideline 202 and similar guidelines. The test was conducted in 100 mL glass beakers maintained at 20 ± 2 °C; pH values ranged from 8.2 to 8.5. First instar daphnids not older than 24 h (10 x 5 animals per concentration) were used. Mortality and sublethal effects were recorded every 24 hours during the test. The accompanying analytical verification of the glufosinate-ammonium concentrations during exposure revealed recoveries of 102% of the corresponding nominal concentration at start of exposure and 100 % at end of the 48 hours exposure period. Since the nominal concentration of 100 mg/L has been successfully maintained over the entire test period all reported results are based on the nominal concentration. No contaminations of glufosinate-ammonium were detected in samples from untreated water control. Due to the absence of treatment related effects up to a nominal concentration of 100 mg a. s. /L, the EC50 for immobilisation after 24 and 48 hours of static exposure was >100 mg a. s. /L.

The acute toxicity of technical grade glufosinate-ammonium (GA; Hoe 039866, purity 97%) to Daphnia magna was tested under static conditions in accordance with U. S. EPA Guidelines (1975) (Forbis, 1985). The test was conducted in 250 mL glass beakers maintained at 20 ± 2 °C; pH values ranged from 8.2 to 8.5. Test concentrations were 0, 32, 56, 100, 320, 560 and 1000 mg/L. Ten first instar daphnids in duplicate were used for each test concentration. Mortality and sublethal effects (as surfacing, clumping of the daphnids together and daphnids lying on the bottom of test chambers) were recorded every 24 hours during the test. No analytical measurements for the test substance were performed during the test. The highest test concentration (1000 mg/L) resulted in 5% mortality. No mortalities or sublethal effects were noted for any other dose group. Thus, the 48 hours EC50 for Daphnia magna was determined to be >1000 mg/L. NOEC was 560 mg/L.

The acute toxicity of technical grade glufosinate-ammonium (GA, AE F039866, purity 96%) was tested on mysid shrimp (Mysidopsis bahia = Americamysis bahia), a saltwater laboratory species in accordance with U. S. EPA 1975 under static conditions (Forbis, 1986). The test system was aged saltwater (salinity 25 – 27%o) maintained at 22 °C and pH 8.0. Nominal test concentrations were 0, 1.0, 1.8, 3.2, 5.6, 10, 18 and 32 mg/L, with ten mysids used per concentration level. The mysids were added to the test chambers by random assignment within 30 minutes after addition of test material. Observations of mortality and abnormal effects such as surfacing, quiescence (immobility) and/or mysids on the bottom were made every 24 hours during the test. The 96 hour EC50 value was determined to be 7.5 mg/L (confidence interval 5.4 – 11 mg/L). NOEC based on mortality and sublethal effects after 96 hours of exposure was 1.0 mg/L. Observed sublethal effects were loss of equilibrium and mysids lying on the bottom of the test vessel. The results were based on nominal concentrations. Analytical measurement of test concentrations was claimed to have been performed on the 10, 18 and 32 mg/L nominal levels.

The acute toxicity of technical grade glufosinate-ammonium (GA; Hoe 039866, purity 97.4%) to Daphnia magna was tested under static conditions in accordance with U. S. EPA Guidelines (1975) in a non-GLP study (Fischer, 1982). The test was conducted in 200 mL glass beakers maintained at 20 ± 1 °C in a temperature controlled area; pH values ranged from 7.11 to 7.68. Test concentrations were 0, 100, 135, 180, 240, 320, 420, 560, 750 and 1000 mg/L. Five first instar daphnids (<24 h old) in duplicate were used for each test concentration. Mortality and abnormal behavioral responses were recorded every 24 hours during the test. The 48 hours EC50 forDaphnia magnawas determined to be 667.56 mg/L (95% CL 595.72 – 747.11 mg/L), the NOEC was 420 mg/L.