Trichloroacetic acid

Endpoint summary

Additional information

Short-term toxicity to fish:

Weight of evidence: Several test results are available. The 96-h LC50 values are in the range from 2000 to 9600 mg/l. The 48-h LC50 values are in the range from 277 to more than 10000 mg/l.

Short-term toxicity to aquatic invertebrates:

Weight of evidence: Several test results are available. For Daphnia magna the following results are provided:

24 h EC50 =110 mg/l

48 h EC50 = 2000 mg/L

96 h EC50 = 3100 mg/l

However, no analytical monitoring was conducted during the studies. Therefore, there is no evidence that the concentration of the substance was maintained during the test.

For the species Nitocra spinipes a 48 h EC50 of 4800 mg/l is provided. Sublethal effects were determined with Dragonfly nymphs (several different species). Significant effects were recorded on the oxygen consumption rate and the ammonia excretion rate.

Toxicity to aquatic algae and cyanobacteria:

Weight of evidence: Read-across from results obtained with the substance sodium trichloroacetate in a non standardized test with several species and read-across from results obtained with the substance monochloroacetic acid in two independent studies according to OECD guideline 201 and DIN 38412, Part 9.

Based on the strongest effects recorded in a 14-day test with the species Chlorella pyrenoidosa and Chlorella mucosa obtained with the substance sodium trichloroacetate (EC50 values of 0.3 and 0.46 mg/l, respectively) and the molecular weights, the read-across approach is applied and the EC50 for trichloroacetic acid is calculated to be 0.27 and 0.4 mg/l for Chlorella pyrenoidosa and Chlorella mucosa, respectively.

Two studies with Scenedesmus subspicatus were independently performed at two different laboratories with the substance monochloroacetic acid. The results for biomass and growth were within the same range, i.e. 25-28 μg/l for biomass and 30-70 μg/l for growth (48-72 hour EC50-values). Based on these results and the molecular weights, the read-across approach is applied and the EC50 (based on growth rate) for trichloroacetic acid is calculated to be between 0.05 and 0.12 mg/l. Taking into account the 72 -h value based on growth rate, as recommended in the CLP Regulation, the EC50 would be 0.12 mg/l for trichloroacetic acid.

Toxicity to microorganisms:

Weight of evidence: Experimental results obtained with the substance trichloroacetic acid and read-across from the results obtained with the analogue sodium trichloroacetate.

In an activated sludge respiration inhibition test, conducted with industrial activated sludge exposed to the substance trichloroacetic acid, the 24 -h EC20 was higher than 750 mg/l.

The luminiscent bacteria toxicity (LBT) test was performed on the marine phosphorescent bacterium Photobacterium phosphoreum. The EC50 for trichloroacetic acid in the LBT test was 35 mg/l. Single species test with Photobacterium phosphoreum (Vibrio fischeri) should be considered of low relevance for STPs (Sewage Treatment Plants).

Based on the results obtained with the substance sodium trichloroacetate and applying the read-across approach taking into account the molecular weights of the substances, it is concluded that for the substance trichloroacetic acid, the toxicity threshold for the species Pseudomonas putida and the 24 -h EC10 for a mixture culture of heterotrophic bacteria would be greater than 880 mg/l. The MIC for the species Aeromonas hydrophila and Bacillus subtilis would be 880 mg/l.

Conclusion:

Trichloroacetic acid is included in the list of harmonised classifications and labellings and it is classified as Hazardous for the Aquatic Environment, Acute Category 1 and Chronic Category 1.

Algae are very sensitive to the analogues sodium trichloroacetate and monochloroacetic acid based on the reported results. These findings support the classification of the substance trichloroacetic acid as Hazardous for the Aquatic Environment, Acute Category 1. Furthermore, since the substance trichloroacetic acid is considered as non readily biodegradable, the substance is also classified as Hazardous for the Aquatic Environment, Chronic Category 1.