COAGULANT 122 (SOLID)

Toxicity to aquatic algae and cyanobacteria

Description of key information

After 72 hours of exposure to Coagulant 122, the EbC50 and ErC50 were 28.5 and 151 mg a.i./l, respectively.
The “no observed effect concentration” (NOEC) for both area under the growth curve and growth rate was not identified during the definitive test but EbC10 and ErC10 of 5.19 and 14.2 mg a.i./l, respectively were calculated. 
In the range finding test, a no-observed effect concentration of 1 mg a.i./l was identified (nominal).

Key value for chemical safety assessment

EC50 for freshwater algae:

151 mg/L

EC10 or NOEC for freshwater algae:

0.332 mg/L

Additional information

Coagulant 122 was registered in (waxy) solid form to UK authority back in 1995. The tests given in previous chapters are performed on the solid form (80.4% solution). Over the years after this registration, risks related to the substance has known better and registrant came to the conclusion that concentrating process of hydroxypropyl hydroxylamine (HPHA/Coag 122) has severe decomposition hazard potential, especially in the presence of trace free base hydroxylamine. The substance is imported as <50% solution and is never marketed in the solid form. For this reason, following test study “Algal Growth Inhibition Assay, 2009” for Chapter 6.1.5 (toxicity to algae and cyanobacteria) is performed on 44% purity liquid form of this substance.

The results mentioned below are based on 2009 studies.

The effect of Coagulant 122 on the growth of the unicellular green alga Pseudokirchneriella subcapitata was assessed under non-axenic conditions.

The study was conducted in accordance with EC Methods for Determination of Ecotoxicity, Annex to Directive 92/69/EEC (O.J. No. L383A, 1992) Part C, Method 3 “Algal Inhibition Test” and Procedure 201 of the “Guidelines for Testing of Chemicals” of the Organisation for Economic Co-operation and Development: Freshwater Alga and Cyanobacteria, Growth Inhibition Test” (2006).

Triplicate algal cultures, with an initial cell density of 1 x 104/ml, were exposed to Coagulant 122 dissolved in algal nutrient medium at nominal concentrations of 1.94, 4.27, 9.39, 20.7, 45.5, 100 and 220 mg a.i./l. The test media were prepared in OECD medium from aqueous stock solutions that were prepared by the direct addition of the test substance to the dilution medium. The cultures were incubated in an orbital incubator under continuous illumination at temperatures ranging from 22.6 to 23.2°C for 72 hours. At the start of the test, the measured levels of Coagulant 122 in samples of the test cultures ranged between 104 and 117% of their nominal values. After 72 hours, the measured levels were maintained at 100 and 220 mg a.i./l but decreased at the lower exposure levels, ranging from below the limit of detection of the analytical method (0.1 mg/l) at 1.94 mg a.i./l to 63% of nominal at 45.5 mg a.i./l. Based on a geometric mean, the overall measured levels were 0.332, 0.708, 4.17, 10.9, 38.1, 98.3 and 249 mg a.i./l.

Cell numbers were counted daily to monitor growth. The test results are expressed in terms of the area under the growth curve and growth rate. The following values were derived from the data:

Area under the growth curve

EbC₁₀ (72 h) : 5.19 mg a.i./l (95% confidence limits, 2.29, 9.28 mg a.i./l)

EbC₅₀ (72 h) : 28.5 mg a.i./l (95% confidence limits, 21.8, 37.1 mg a.i./l)

Average specific growth rate

ErC₁₀ (0 - 72 h) : 14.2 mg a.i./l (95% confidence limits, 9.63, 18.8 mg a.i./l)

ErC₅₀ (0 - 72 h) : 151 mg a.i./l (95% confidence limits, 136, 169 mg a.i./l)

No observed effect concentration (NOEC): < 0.332 mg a.i./l

Based on statistical analysis, a no-observed-effect concentration was not identified during the definitive test. However, inhibition at the three lowest test levels was similar so the reduction observed in growth at these levels may not be of biological significance as growth in a number of the replicate cultures at nominal 4.27 and 9.239 mg a.i./l was similar to that in the control cultures. In the range finding test, algal growth was not inhibited at nominal 1 mg a.i./l.

The mean coefficient of variation (CoV) for daily growth rates in control cultures ranged between 4.1 and 7.7 during the definitive test and the CoV for the average specific growth rates of control culture was 1.7 during the 72-hour exposure period.

No microscopic abnormalities of the cells were detected.

The measurements of water quality remained within acceptable limits throughout the study. The temperature of the incubator ranged between 22.6 and 23.2°C. At the start of the test, the test media at all concentrations were colourless.