1-(2,6-bis(4-tolyl)-1,3-dioxano(5,4-d)-1,3-dioxan-4-yl)ethane-1,2-diol

Toxicity to aquatic algae and cyanobacteria

Description of key information

algal growth inhibition: EC50 values of greater than 0.40 mg/l and No Observed Effect Concentration of 0.40 mg/l

Key value for chemical safety assessment

EC50 for freshwater algae:

0.4 mg/L

EC10 or NOEC for freshwater algae:

0.4 mg/L

Additional information

Introduction.

A study was performed to assess the effect of the test material on the growth of the green alga Desmodesmus subspicatus. The method followed that described in the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

Methods. 

Information provided indicated the test material had a water solubility value of 1.5 x 10^-3g/l. A pre-study media preparation trial showed that the use of a saturated solution method of preparation resulted in the highest dissolved test material concentration.

Following a preliminary range-finding test, Desmodesmus subspicatu swas exposed to a solution of the test material at a measured test concentration of 0.40 mg/l (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C. The test material solution was prepared by stirring an excess (50 mg/l) of test material in culture medium using a propeller stirrer at approximately 1500 rpm at a temperature of 21°C for 24 hours. After the stirring period any undissolved test material was removed by filtration (0.2 µm Sartorius Sartopore filter, first approximate 2 litres discarded in order to pre-condition the filter) to produce a saturated solution of the test material with a nominal concentration of 0.40mg/l*.

*Concentration determined by analysis of a saturated solution prepared in an identical manner during the pre-study media preparation trial.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter Multisizer Particle Counter.

A positive control conducted approximately every six months used potassium dichromate as the reference material. Desmodesmus subspicatus was exposed to an aqueous solution of the reference material at concentrations of 0.0625, 0.125, 0.25, 0.50 and 1.0 mg/l (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter Multisizer Particle Counter.

Results. 

Exposure of Desmodesmus subspicatus to the test material gave EC₅₀ values of greater than 0.40 mg/l and correspondingly the No Observed Effect Concentration was 0.40 mg/l.

Analysis of the test preparations at 0 and 72 hours showed measured test concentrations to be near nominal and so the results are based on nominal test concentrations only.

This study showed that there were no toxic effects at saturation.

Exposure of Desmodesmus subspicatus to the reference material, potassium dichromate, gave an E_rC₅₀(0 - 72 h) of 0.49 mg/l; 95% confidence limits 0.43 – 0.55 mg/l, an E_yC₅₀(0 - 72 h) of 0.22 mg/l; 95% confidence limits 0.19 ‑ 0.24 mg/l, and an E_bC₅₀(0 - 72 h) of 0.23 mg/l; 95% confidence limits 0.21 - 0.27 mg/l. The Lowest Observed Effect Concentration based on inhibition of growth rate, yield and biomass integral were 0.25, 0.125 and 0.125 mg/l respectively and the No Observed Effect Concentrations were 0.125, 0.0625 and 0.0625 mg/l respectively.