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, iBA is estimated to be also acutely toxic to saltwater fish.
LC50 (96 h, flow through) = 2.1 mg/L (measured) (Pimephalis promelas, ASTM 1980)
LC50 (96 h, flow through) = 2.1 mg/L (measured) (Cyprinodon variegatus, OECD 203) (n-butyl acrylate)

Additional information

Isobutyl acrylate was tested in an 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).

As 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 was approx. 22 mg/L. In this study conducted in open test vessels, under static conditions and without analytical monitoring, the volatility of iBA was not taken into consideration. Thus, this study is only valid with restrictions.

In addition, 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 rainbow trout was determined to be 5.2 mg/L based on the mean measured concentrations (BAMM, 1990). This study followed OECD Guideline 203 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 rainbow trout 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 study conducted with n-butyl acrylate in the sheepshead minnow (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 butyl acrylate/L treatment groups, respectively. Although no mortality was observed in the 1.3 mg butyl acrylate/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 butyl acrylate/L treatment group, the NOEC was considered to be 1.3 mg butyl acrylate/L.

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.

In addition, a robust data set of acute studies is available from the other members of the acrylic ester category (methyl, 2-ethylhexyl, ethyl, and tert-butyl acrylate).