1,4-dihydroxy-2,2,6,6-tetramethyl piperidinium-2-hydroxy-1,2,3-propanetricarboxylate

Toxicity to aquatic algae and cyanobacteria

Description of key information

The No-Observed-Effect Concentration(NOEC) was empirically estimated to be 74 mg a.i./L. The 72-hour ErC50 was calculated to be 380 mg a.i./L (corresponding 95% confidence limits of 110 to 1400 mg a.i./L).

Key value for chemical safety assessment

EC50 for freshwater algae:

380 mg/L

EC10 or NOEC for freshwater algae:

74 mg/L

Additional information

The purpose of this study according to OECD TG 201A adopted 1984-07-06 was to determine the effect of the test item on the growth of the freshwater green algae, Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum). Test concentrations were selected based on the results of preliminary testing. Based on these results nominal test concentration chosen for the definitive study were 10, 26, 64, 160, 400, and 1000 active ingredient per liter of test solution (mg a.i./L). Mean measured concentrations ranged from 95 to 120% of nominal concentrations and defined the treatment levels as 11, 31, 74, 150, 390, and 1000 mg a.i./L.At test initiation (0 hour) and test termination (96 hours), one sample from each exposure solution and the control was analyzed for test item concentrations. All samples were analyzed for the test item using a gas chromatography (GC) procedure based on methodology. Cell densities were determined at each observation interval. Cell density in the 11, 31, 74, 150, 390 and 1000 mg a.i./L treatment levels averaged 317, 298, 263, 30, 6.8, and 3.6 x 10E4 cells/mL, respectively, at test termination, statistical analysis (i.e., Williams' Test) demonstrated a significant reduction in cell density in treatment levels >31 mg a.i./L as compared to the control data. Based on these results, the 96- hour NOEC for cell density was determined to.be 11 mg a.i./L. The 96-hour EC50 for cell density was calculated to be 110 mg a.i./L (corresponding 95% confidence limits of 42 to 290 mg a.i./L). Cell biomass was calculated as area under the growth curve. The biomass in the 11, 31, 74, 150, 390 and 1000 mg a.i./L treatment levels averaged 102, 95, 90, 13, 5.6, and 2.2 x 10E4 cells days/mL, respectively. Statistical analysis (Williams' Test) determined a significant difference in biomass at treatment levels >31 mg a.i./L when compared to the biomass in the control. Based on these results, the NOEC for biomass was determined to be 11 mg a.i./L. The 72-hour EbC50 for biomass was calculated to be 120 mg a.i./L (corresponding 95% confidence limits of 39 to 400 mg a.i./L). The growth rate in the 11, 31, 74, 150, 390 and 1000 mg a.i./L treatment levels averaged 1.60, 1.58, 1.56, 0.850, 0.605, and 0.511 days/mL respectively. Statistical analysis (Kruskal-Wallis Test) determined a significant difference in growth rate at the 1000 mg a.i./L treatment level when compared to the growth rate in the control. No-Observed-Effect Concentration (NOEC) was empirically estimated to be 74 mg a.i./L where a 2.3% reduction in growth rate relative to the control was observed. The 72-hour ErC50 was calculated to be 380 mg a.i./L (corresponding 95% confidence limits of 110 to 1400 mg a.i./L).