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Ecotoxicological information

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The dicarboxylic acids are of weak to medium acidity and partly dissociate in water causing a pH shift (pKa1: 4.21-4.43; pKa2: 5.42-5.64). The tolerance of water organisms towards pH is diverse. Recommended pH values for test species listed in OECD guidelines are between 6 and 9.

Concerning ecotoxicity of the multi constituent substance “dicarboxylic acids” in the environment, adipic acid is applied for read-across approach. Adipic acid is one of the constituents of the dicarboxylic acid mixture. All constituents are homologues linear alkyl dicarboxylic acids with a chain length of four to six carbon atoms. The mixture is composed of three discrete carboxylic acids. Due to the structural relationship, adipic acid is a good representative for the dicarboxylic acid mixture. Adipic acid is well assessed on behalf of the ICCA/OECD HPV-program, and adequate information already exits to satisfy the requirements under REACH for each endpoint. Where no data are available for the dicarboxylic acid mixture, data gaps were filled using the data of adipic acid.

Acute toxicity of the mixture of dicarboxylic acids to fish (Danio rerio) was assessed in a static bioassay according to a method comparable to the OECD Guideline 203 (Fish, Acute Toxicity Test). After 96 hours of exposure, a LC50 of 59.5 mg/l was obtained (Bayer, 1988).

With respect to the toxicity towards invertebrates (Dapnia magna) test results from adipic acid were used to draw a conclusion on toxicity to invertebrates. In static test conducted according to the OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) an 48 h-EC50 of 46 mg/l (MITI, 1997) was determined.

The long-term toxicity of adipic acid towards aquatic invertebrates (Dapnia magna) was investigated in a reproduction test according OECD Guideline 211. After 21 days of exposure a NOEC-reporduction of 6.3 mg/l was determined (MITI, 1997).

Concerning the toxicity to algae, the fresh water alga Scenedesmus subspicatus was exposed to the mixture of dicarboxylic acids for 72 hours. The experiment was conducted according to a national standard method and gave a 72-h EC50 value for effects on growth rate of 41.9 mg/L and a 72 -h EC10 of 22.6 mg/L (MITI, 1997).

Assessing the toxicity towords microorganisms, growth inhibition tests with Tetrahymena pyriformis were performed using adipic-, or succinic- or glutaric acid in each test. An 40h-IC50 of 591 mg/L was observed for adipic acid, 574 mg/l for succinic acid and 1027 mg/l for glutaric acid. (Schultz, 1997).