Isobutyl acrylate

Short-term toxicity to fish

Description of key information

Isobutyl acrylate is acutely toxic to freshwater fish. Based on data from the structural analogue n-butyl acrylate, isobutyl acrylate is estimated to be also acutely toxic to saltwater fish.
LC50 (96 h, flow through) = 2.1 mg/L (measured) (Pimephalis promelas, ASTM 1980) (isobutyl acrylate)
LC50 (96 h, flow through) = 2.1 mg/L (measured) (Cyprinodon variegatus, OECD 203) (n-butyl acrylate)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

2.1 mg/L

Marine water fish

Marine water fish

Effect concentration:

2.1 mg/L

Additional information

Experimental data are available for the target substance isobutyl acrylate (CAS 106 -63 -8) as well as for the source substances tert-butyl acrylate (CAS 1663 -39 -4) and n-butyl acrylate (CAS 141 -32 -2).

 

Isobutyl acrylate

Isobutyl acrylate was tested in a 96-hour acute toxicity test with Pimephalis promelas under flow-through conditions. Biological and chemical procedures followed the American Society for Testing and Materials recommendations (ASTM, 1980). The test was repeated once. Based on mean measured concentrations, the 96-hour LC50 was determined to be 2.09 and 2.11 mg/L, respectively. Reported behavioural effects were: hyperactive locomotor activity, overreactivity to outside stimuli, tetany, with no signs of permanent deformities (lordosis/scoliosis) (Russom et al., 1988).

A supporting study, an acute fish test according to the national German standard DIN 38412, part 15 with Leuciscus idus is available. The 96-hour LC50 based on nominal concentrations of 2.15, 4.64, 10.00, 21.50, 46.40 and 100 mg/L was approx. 22 mg/L (BASF AG, 1989). In this study conducted in open test vessels, under static conditions and without analytical monitoring, the volatility of isobutyl acrylate was not taken into consideration. Thus, this study is only valid with restrictions.

 

Another study is available with a 96-hour acute toxicity test with Pimephalis promelas under static conditions comparable to standard methods for the examination of water and wastewater 13th edition, 1971 American Public Health Assn.NY, NY 10019 (Dow Chem. Co., 1992). The 96-hour LC50 was nominal determined to be in the range of 10-20 mg/L. Due to poor documentation the reliability of the study is not assignable and hence not considered for assessment.

 

N-butyl acrylate

Valid experimental data from the structural analogue n-butyl acrylate are available which support the LC50 of approx. 2.1 mg/L published by Russom et al. (1988).

 

The 96-hour LC50 for n-butyl acrylate in Oncorhynchus mykiss was determined to be 5.2 mg/L based on the mean measured concentrations (BAMM, 1990). This GLP compliant study followed EPA OTS 797.1400 guideline using a flow-through design. Nominal exposure concentrations ranged from 0.438 to 14 mg/L and mean measured concentrations (0 and 96 hrs) ranged from 0.49 to 7.2 mg/L. Behavioral/sublethal effects noted during the study included surfacing, labored respiration, quiescence, on-bottom orientation and loss of equilibrium. A no-effect concentration (NOEC) of n-butyl acrylate toxicity to Oncorhynchus mykiss was determined to be 3.8 mg/L, based upon behavioral and sublethal effects at 14 and 7.2 mg/L. The lack of mortality or behavioral/sublethal effects at the test concentrations of 3.8, 1.9, 0.93 and 0.49 mg/L supported this conclusion.

 

In a saltwater GLP study conducted with n-butyl acrylate in Cyprinodon variegatus (BAMM, 1996), the 96-hour LC50 was estimated to be 2.1 mg/L. This study was conducted according to OECD Guideline 203 using a flow-through design. The LC50 value was based on analytically determined concentrations. After 96 hours of exposure, mortality was 0, 100 and 100 % in the 1.3, 3.5 and 5.1 mg n-butyl acrylate/L treatment groups, respectively. Although no mortality was observed in the 1.3 mg/L treatment group, the majority of the fish were exhibiting clinical signs of toxicity at test termination (e.g., lethargy, erratic swimming and surfacing). Due to the clinical signs of toxicity observed in the 1.3 mg/L treatment group, the NOEC was considered to be 1.3 mg butyl acrylate/L.

 

Tert-butyl acrylate

A freshwater non GLP compliant study conducted with tert-butyl acrylate according to national German standard DIN 38412, part 15 using a static design is available (BASF SE, 1978). In this test with Leuciscus idus there was no analytical monitoring, so the test concentrations (0 (control), 1.78, 2.15, 2.61, 3.16, 3.83 and 4.64 mg/L) were recalculated based on the geometric means of the nominal concentrations at test start. Thus the 96-hour LC50 was determined to be 2.37 mg/L.

 

Conclusion

Since isobutyl acrylate is readily biodegradable and of moderate volatility, exclusively effect values based on analytically measured test concentrations are considered valid for hazard assessment purposes. Based on the most relevant and reliable information on toxicity to freshwater fish (ASTM, 1980) the 96 -hour LC50 is considered to be 2.1 mg/L. This result is supported by valid experimental data from the structural analogue n-butyl acrylate (BAMM, 1990; 96 h LC50 = 5.2 mg/L). By applying a read across approach to the structural analogue n-butyl acrylate (BAMM, 1996), the 96 -hour LC50 for marine water fish of the target substance isobutyl acrylate is determined to be 2.1 mg/L. In conclusion, isobutyl acrylate is regarded to be acutely toxic both to freshwater and marine fish.