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GLP-studies are available concerning the toxicity of acetyl tributyl-citrate to fish, aquatic invertebrates and algae: Short-term effects were investigated with fresh- and salt water fish and with a freshwater crustacean species in standard tests. Furthermore, a limit test on chronic toxicity to daphnids is available.

 

For assessing short-term effects on fish, reliable 96 h LC50 values are available from 2 flow-through tests. The 96-hour LC50 for the saltwater species Fundalus heteroclitus was 59 mg/L and for the fresh water species Lepomis macrochirus the LC50 values ranged between 38 and 60 mg/L. Both test results were based on nominal concentrations. The test concentrations were chemically analysed, however, the recovery of the test substance was unsatisfactory in the short-term tests and nominal concentrations were used for the evaluations.

The lowest LC50 value obtained in the fish studies was considered most relevant for the aquatic hazard assessment:

96 h LC50 Lepomis machrochirus 38 mg/L.

 

For assessing short-term effects on crustaceans, two reliable short-term tests are available. Immobilisation of Daphnia magna was studied in a static test according to OECD 202. Test solutions up to 1 mg/L (the maximum soluble concentration) were applied, ethanol was used as vehicle. After 24 h no immobilisation was observed in all test solutions.

 

The toxicity of tributyl acetylcitrate towards algae was investigated in a study conducted with Desmodesmus subspicatus according to EU Method C.3 (Algal Inhibition test; 2008) and OECD Guideline 201 (Alga, Growth Inhibition Test; 2006). Based on the results of a screening test, test substance concentrations of 10, 20, 40, 80, and 100 mg/L nominal were used. Due to the poor water solubility of the test substance water accommodated fractions were prepared and used in the tests. The stability of the test substance was checked by IR measurements. Based on the comparison of test substance concentrations/recoveries at time 0 and after 72h it can be concluded that the test substance was stable during the test duration (recovery around 80%). Based on this, the reported effect concentrations refer to mean measured (arithm. mean) concentrations of the aqueous phase. In respect to both, growth rate and yield, the 72 h NOEC and LOEC values were determined to be 4.65 and 10.9 mg/L, respectively. The 72 h EC50 for growth rate was determined to be 74.4 mg/L. In respect to yield, the 72 h EC50 was determined to be 11.5 mg/L (95% C.I. for both parameters could not determined).

 

The toxicity of tributyl acetylcitrate towards activated sludge was investigated in a study conducted according to EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test; 2008) and OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test; 1984). Based on the results of a screening test, the definitive test was performed as a limit test using three parallels with the highest nominal concentration of ca. 1000 mg/L. A fourth flask containing test substance (1006 mg/L), tap water and synthetic sewage feed was used for testing autoxidation of the test substance. At the concentration tested no inhibitory effects were observed (3 h EC10>1000 mg/L nominal).

No studies on long-term effects on aquatic organisms are available. 

In a chronic test on invertebrates, the influence of ATBC on the survival and reproduction rate of Daphnia magna was determined during an exposure period of 21 days. The 21-day NOEC was determined to be ≥ 1.11 mg test item/L for the reproduction rate and ≥ 1.11 mg test item/L for the survival of the adult test animals, respectively. The EC50 for the reproduction rate was > 1.11 mg test item/L.

 

Determination of PNECaquatic organisms freshwater

Short-term data for species from three trophic levels, a study on chronic toxicity to daphnia toxicity as well as a NOEC for algal growth are available for acetyl tributyl citrate (ATBC). In this case an assessment factor of 50 has to be applied.

The most sensitive endpoint was the 21d-NOEC from a limit test with Daphnia magna of ≥ 1.11 mg test item/L.

PNECaqua freshwater= 1.11 mg ATBC/L / 50 = 22 µg ATBC/L

 

Determination of PNECaquatic organisms marine

The greater species diversity in the marine environment compared to freshwater, including the presence of a number of taxa that occur only in that environment, may mean that the distribution of sensitivities of species is broader. Therefore, an assessment factor of 500 is applied to the most sensitive NOEC.

PNECaqua marine= 1.11 mg ATBC/L / 500 = 2.2 µg ATBC/L

 

Determination of PNECmicroorganism

There is a 3 h-EC10 of>1000 mg/L available, obtained from an Activated Sludge Respiration test. Using an assessment factor of 10, the PNEC is calculated to

PNECmicroorganism= 1000 mg ATBC/L / 10 = 100 mg ATBC/L

 

Determination of PNECsediment

The available data set does not include a single data on the effects of acetyl tributyl citrate on sediment organisms. The PNEC may provisionally be calculated using the equilibrium partitioning method with the PNEC for aquatic organisms and the water/sediment partioning coefficient.