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Diss Factsheets

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Isotan is an organic salt of strong base NaOH and weak acid causing a pH-shift in water. The tolerance of water organisms towards pH is diverse. Recommended pH values for test species listed in OECD guidelines are between 6 and 9.

Acute toxicity to fish (Brachydanio rerio) was determined in accordance with the Council Regulation (EC) No 440/2008, Method C.1 'Acute toxicity for Fish' (2008) which is in most parts equivalent to the OECD Guideline for Testing of Chemicals No. 203 'Fish, Acute Toxicity Test' (1992). Groups of seven fish of the recommended size were exposed to a range of concentrations, nominally 9.4; 20.7; 45.5 and 100 mg/L of Isotan, dissolved in water of pH value 6.0 under semi-static conditions. Observations were made on the numbers of dead fish and the incidence of sub-lethal effects. After 96 h LC 50-values of 60.01 mg/l for the active ingredient and 65.86 mg/l for the drying residue (geometric mean measured concentrations) were measured.

Concerning the toxicity towards aquatic invertebrates, an acute toxicity test to Daphnia magna was taken into account to draw a conclusion on toxicity towards aquatic invertebrates for Isotan. The study was performed in accordance with the Council Regulation (EC) No 440/2008, Method C.2 'Acute toxicity for Daphnia' (2008) which is in most parts equivalent to the OECD Guideline 202 (Daphnia sp. Acute Immobilization Test). Daphnia magna was exposed under semi-static conditions to a range of concentrations of the test item (pH 6.0-7.0). After 48h EC 50-values of 24.7 mg/l for the active ingredient and 27.1 mg/l for the drying residue were (geometric mean measured concentrations) were measured.

In a test, the fresh water alga Scenedesmus subspicatus was exposed to Isotan for 72 hours under static conditions (pH 6.1-7.2). The study was conducted in accordance with Commission Regulation (EC) No 761/2009 amending Regulation No 440/2008, Method C.3 ‘Freshwater Algae and Cyanobacteria, Growth inhibition test’ (2009) which is equivalent to OECD Guideline for Testing of Chemicals No. 201 'Alga, Growth Inhibition Test' (2006). Exponentially growing algal cells were exposed for a period of 72 hours to a range of concentrations, nominally 0.32, 1.0, 3.2, 10 and 32 mg/L of the test item dissolved in water. The cell densities were measured at 24 hour intervals. The study data were analyzed on a 48 h basis. As cell numbers increased well above 16-fold over 48 h, and all other validity criteria are met, this is an option explicitly covered by OECD TG 201 (2006) and EU method C.3 (2009). After 48 h EC 50-values of > 100 mg/l for the active ingredient and the drying residue (geometric mean measured concentrations) were measured.

In order to test the toxicity to microorganism of the substance, activated sludge from predominantly domestic sewage plant was exposed to the test solution of five nominal concentrations of the substance (100, 180, 320, 560, 1000 mg/l), blank control solution and solution with positive reference substance for a period of 3 hours. Dissolved oxygen was recorded and respiration rates were calculated. 49.0 % respiration inhibition was observed at the highest concentration of test substance as water solution. Analysis of the respiration rates after 3 hours (by probit analysis) gave an EC 50 value of 978.2 mg/l and an EC 10-value of 85.0 mg/l. As the content of the active ingredient in the water solution is 36.5% the effect concentrations can be calculated for the pure and solid substance as EC50= 357.0 mg/L and EC10= 31.03 mg/L. The study was conducted in accordance with Council Regulation (EC) No 440/2008, Method C.11 ”Activated sludge respiration inhibition” (2008). This test method is equal to OECD Guideline 209 (1984).

All toxicity studies mentioned above are evaluated as acceptable and satisfy the guideline requirements for the toxicity studies on acute toxicity to aquatic organisms.