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Short-term toxicity to aquatic invertebrates

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Description of key information

Tert-butyl acrylate is acutely toxic to freshwater invertebrates.

EC50 (48 h) = 8.74 mg/L (measured), (Daphnia magna, OECD TG 202, closed system)

Key value for chemical safety assessment

Additional information

An acute toxicity study with Daphnia magna (BASFSE, 2001) indicated the 48-hour EC50 was 8.74 mg/L based on mean measured concentrations. This study followed OECD TG 202, part I using a static design (closed system). Nominal exposure concentrations ranged from 3.13 to 100 mg/L. The analytical recovery rate was after 0h and 48 h in all analyzed test solutions below 80 %. The effective concentrations mentioned in the study report were based on a median analytical recovery rate in the range of the beginning effect (12.5 mg/L) between 0h and 48 h (46 %). Complete immobilization occurred at the second highest concentration (23 mg/L, measured). The NOEC was 5.75 mg/L (measured).

In a short-term test with Daphnia magna conducted according to the Directive 84/449/EEC, C.2, the 48-hour EC50 was determined to be 57 mg/L based on nominal concentrations (BASF AG, 1993). Since this study was performed in an open test system and without concentration control analysis, the respective test result is valid with restrictions.

Since tert-butyl acrylate is of considerable volatility and moderately biodegradable, only test results from studies with analytical monitoring and performed in closed system were used for the hazard assessment for freshwater invertebrates.

Supporting data from other acrylates

In addition, a robust data set of acute studies is available from other acrylic esters (2-ethylhexyl acrylate, ethyl acrylate, n-butyl acrylate and methyl acrylate).

The acute toxicity of ethyl acrylate and n-butyl acrylate to aquatic invertebrates were determined in two separate studies performed according to EPA OTS 797.1300 that were in compliance with GLP (BAMM, 1990; BAMM 1990). In these studies, daphnids (Daphnia magna) were exposed to test concentrations in flow-through tests for a period of 48 hours. Test concentrations were analytically verified, but did not remain within 80 - 120% of the nominal concentrations. Therefore, the effect concentrations are based on the arithmetic means of the measured concentrations. Immobilization was recorded after 24 and 48 hours exposure. For ethyl acrylate, no abnormalities other than immobilization was observed and immobility was observed in the two highest concentrations. For n-butyl acrylate, immobility was observed in the three highest concentrations. Immobility increased in a dose-depenent manner with increasing test concentrations for both compounds. Based on these results, the 48-h EC50 were determined to be 7.9 and 8.2 mg/L for ethyl acrylate and n-buty acrylate, respectively.

The acute toxicityh of methyl acrylate to aquatic invertebrates was assessed in two studies according to EPA OTS 797.1930 and OECD 202, respectively (BAMM 1996, BAMM 1995). In these studies, the saltwater mysid (Americamysis bahia) and freshwater waterflea (Daphnia magna) were exposed for 96 and 48 hours, to test concentrations up to 9 and 10 mg/L (nominal). Mortality (saltwater mysid) and immobility (daphnids) was determined daily. Test concentrations were analytically verified, but did not remain within 80 - 120% of the nominal concentrations. Therefore, the effect concentrations are based on the arithmetic means of the measured concentrations. Saltwater mysids were lethargic and showed erratic swimming in the two highest test concentrations which were also the concentrations at which mortality was observed after 96 hours. In the freshwater test, several daphnids were observed as floating during the test which were submerged with a drop of water. These effects were determined to be not treatment-related. Immobile daphnids were observed in the four highest concentrations. Based on these results, the 96-h EC50 and 48-h EC50 were determined to be 1.6 and 2.6 mg/L for the saltwater mysid and daphnids, respectively.

Furthermore, the toxicity of 2-ethylhexyl acrylate to aquatic invertebrates was determined in a static test, performed according to OECD 202 and in compliance with GLP criteria. In this study, daphnids (Daphnia magna) were exposed to nominal test concentrations of 0 (control), 3.13, 6.25, 12.5, 25, 50 and 100 mg/L. Immobility of the test organisms was determined after 24 and 48 hours exposure. Test concentrations were analytically verified, but did not remain within 80 - 120% of the nominal concentrations. Therefore, the effect concentrations are based on the arithmetic means of the measured concentrations. Immobile daphnids were observed from 25 mg/L after 48 hours, which increased in a dose-dependent manner. Based on these results, the 48-h EC50 was determined to be 1.3 mg/L.

Overall, the data of other acrylates supports the finding of the acute toxicity test with tert-butyl acrylate (BASFSE, 2003). Members of the acrylic ester category show comparable toxicity values towards aquatic invertebrates.