Ammonium 2-amino-4-(hydroxymethylphosphinyl)butyrate

Long-term toxicity to fish

Description of key information

NOEC (35 d) = 26.2 mg a.s./L (mean measured) (Pimephales promelas; FIFRA 72-4m 1982; OCSPP 850.1400, 1996 draft; OECD 210, 1992) (Banman et al., 2014)

Additional information

Two studies on the chronic toxicity of glufosinate-ammonium to fish are available. Both studies were conducted according to GLP and different international guidelines. Two species of freshwater fish (Pimephales promelas, Oncorhynchus mykiss) were tested.

For studies already evaluated for the last Annex I listing, which are considered relevant in the context of classification and labelling, summaries are taken form the DAR (2002) and its Addenda (2004). The information on new data form the Annex I renewal process relevant for the classification and labelling with regard to aquatic toxicity (Banman, C.S. et al. (2014), M-507827-01-1) is presented within this dossier as summarised in the Document MCA for Annex I renewal.

 

The purpose of the study by Banman et al. (2014) was to estimate the chronic toxicity of glufosinate ammonium to early life stages of Fathead minnow (Pimephales promelas) under flow-through conditions. The study was conducted according to FIFRA Guideline 72-4 (1982), OCSPP Guideline 850.1400 (1996 draft) and OECD Guideline 210 (1992). This test resulted in the most sensitive effect values and is chosen as key study.

Fathead minnow (Pimephales promelas) eggs starting at <24 hours old were observed for hatch rate; young fish were assessed for abnormal behaviour, physical changes, mortality and growth (length, dry weight); study duration was 35 days under flow through conditions. This project consisted of two in-life trials due to variable statistical significance for the dry weight measurement in the initial study, making interpretation of the toxicity problematic. Trial 1: Nominal concentrations (mean measured) were: Control (<0.100), 3.44 (3.03), 6.88 (6.12), 13.75 (12.2), 27.5 (26.2), 55 (51), 110 (101) mg a.s./L. Mean measured recoveries ranged from 88 to 95% of nominal values. Results are based on mean measured concentrations. Trial 2: Nominal concentrations (mean measured) were: Control (<0.100), 0.938 (0.874), 1.88 (1.76), 3.75 (3.39), 7.50 (7.33), 15.0 (14.6) and 30.0 (28.3) mg a. s. /L. Mean measured recoveries ranged from 90 to 98% of nominal values. Results are based on mean measured concentrations.

Statistically significant effects occurred for the length and dry weight endpoints in Trial 1. The length NOEC was 26.2 mg a. s. /L. For the dry weight endpoint, there was not a clear monotonic dose response, and statistically significant effects occurred in the 3.03, 12.2, and 101 mg a. s. /L treatment groups. These effects were considered spurious and not biologically relevant. There were no statistically significant effects for any of the treatment levels in Trial 2. The overall LOEC and NOEC for this trial were > 28.3 and ≥ 28.3 mg a. s. /L, respectively.

Observations of fish were recorded daily throughout trials 1 and 2. Fish in all test levels appeared normal during the course of the study, with the exception of a few fish small in size, with erratic swimming behavior and with scoliosis being noted throughout various test vessels. In respect to trial 2, the observations noted above did not follow a monotonic pattern and only pertained to a few fish which were spread throughout the controls and treatment groups. The incidence of these observations increased and included some fish with loss of equilibrium in the two highest treatment levels from trial 1 (51 and 101 mg a. s. /L) which may have been a physical response to the chemical exposure.

In conclusion, the 35-day exposure to glufosinate-ammonium resulted in a NOEC of 26.2 mg a. s. /L and a LOEC of 51 mg a. s. /L.

 

The toxicity of glufosinate-ammonium technical (code Hoe 039866, purity 99%) was tested on Oncorhynchus mykiss in a 21-day prolonged toxicity test under flow-through conditions generally in accordance with OECD Guidelines 204 (version 1984) (Fischer, 1989). At test start fish were five months old and had an average length of 51 mm. The test water was aerated to oxygen saturation and maintained at 14 ± 1 °C, pH was 7.8 - 8.1. Nominal test concentrations were 0, 5, 10, 50, 100, 500, and 1000 mg/L. Ten fish were tested for each concentration, with no replicates. Analyses of test substance were conducted by HPLC at the concentrations of 5, 50, 100 and 500 mg/L on test days 4, 11, and 18. Mortality, growth and occurrence of sublethal effects were noted at 24 hours interval for 21 days.

The recovery rate of active substance according to the HPLC-analysis was 86 – 99%. As the measured concentrations remained above 80% of the nominal concentrations, all results are reported as nominal concentrations. Observations made during the test indicated that some fish in the concentration of 500 mg/L showed slow reactions, head down or surface swimming, horizontal turns, and/or narcotic symptoms during the first six test days, followed by 100% mortality. At 1000 mg/L, total mortality was observed already in the first test day. On test day two the fish in the concentration of 100 mg/L showed slow reactions, but the effects were not seen later during the test. Slight differences in size and weight were not dose related. The highest concentration tested without mortality or significant sublethal effects (NOEC, no observed effect concentration) was concluded to be 100 mg/L. The 21 days LC50 was calculated to be 224 mg/L.