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Toxicity to aquatic algae and cyanobacteria

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Description of key information

n-Butyl acrylate is acutely toxic to freshwater algae.
EC50 (72 h, cell number) = 2.65 mg/L (measured) (Selenastrum capricornutum, OECD TG 201)

Key value for chemical safety assessment

Additional information

An acute toxicity study was conducted with Selenastrum capricornutum (BAMM, 1990) according to OECD Guideline 201 using a static design. Nominal exposure concentrations were 3.8, 7.5, 15, 30, 60 mg/L. At time 0, the analyzed concentrations were 3.5, 7.2, 15, 32, 67 mg/L. After 96 hours, analyses of the test media were all below the limit of detection. The loss of butyl acrylate was considered to be related to volatility and/or adsorption to the vessels and the algae. Growth inhibition of algae was observed at all concentrations from 24 through 96 hours. At termination, the cell counts for the 3.5, 7.2, 15, 32, 67 mg/L cultures were 100, 15, 2.8, 0.82, and 0.59 cells/mL (x 104), respectively. Based on cell counts, the 72 and 96 hour EC50 values were 5.9 and 5.2 mg/L, respectively. All results were based on nominal test concentrations of butyl acrylate since samples taken at 96 hours were below the detection limit of n-butyl acrylate.

A recalculation using the arithmetic means for the exposure concentrations (1.8, 3.15, 7.55, 16.5, 34 mg/L) provides a 96-hour EC50 value of 2.65 mg/L. This value indicates the toxicity of butyl acrylate to algae is similar to other aquatic species and the recalculated EC50 is considered appropriate for the assessment. No NOEC could be derived since significant growth inhibition was observed at all concentrations (< 1.8 mg/L).

Two additional studies were available, but were considered to be klimisch 3 as these studies did not meet important criteria of standard methods.

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