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The aquatic toxicity of the six acrylic esters (methyl, 2-ethylhexyl, ethyl, n-butyl, isobutyl, and tert-butyl acrylate) is evaluated as a category.

 

Data of the acute toxicity in freshwater organisms are available for all three trophic levels (fish, aquatic invertebrates and algae). Effect values were all in the same range of concentrations, i.e. between 1 and 10 mg/L.

 

Freshwater fish

LC50 values for Oncorhynchus mykiss were determined to be 3.4 mg/L (measured) for methyl acrylate (BAMM 1995), 1.81 mg/L (measured) for 2-ethylhexyl acrylate (BASF AG 1999), and 4.6 mg/L (measured) for ethyl acrylate (BAMM 1990), respectively. The LC50 value for Salmo gairdneri was 5.2 mg/L (measured) for n-butyl acrylate (BAMM 1990) and the LC50 value for Pimephalis promelas was approx. 2.1 mg/L (measured) for isobutyl acrylate (Russom et al. 1988). Tert-butyl acrylate was tested in an acute toxicity study with Leuciscus idus under static test conditions without analytical monitoring and in an open system (BASF AG, 1978). Test concentrations were recalculated based on the nominal test concentrations at test start and the assumption that at test termination all concentrations were below the limit of detection (0.1 mg/L) as worst case. The 96-hour LC50 was recalculated to be 2.37 mg/L.

 

Thus, LC50 values for freshwater fish were between 1.81 and 5.2 mg/L.

Freshwater invertebrates

EC50 values for Daphnia magna were 2.6 mg/L (measured) for methyl acrylate (BAMM 1995), 1.3 mg/L (measured) for 2-ethylhexyl acrylate (BASF AG 2001), 7.9 mg/L (measured) for ethyl acrylate (BAMM 1990), 8.2 mg/L (measured) for n-butyl acrylate (BAMM 1990), and 8.74 mg/L (measured) for tert-butyl acrylate (BASF AG, 2001), respectively. No acute toxicity studies in invertebrates involving analytical monitoring are available for isobutyl acrylate.

 

Thus, EC50 values for freshwater invertebrates were between 1.3 and 8.74 mg/L.

 

Freshwater algae

EC50 values for Selenastrum capricornutum were 3.55 mg/L (measured) for methyl acrylate (BAMM 1995), and 4.5 mg/L (measured) for ethyl acrylate (BAMM 1990) based on growth rate, and 2.65 mg/L (measured) for n-butyl acrylate (BAMM 1990) based on cell number, respectively. The EC50 (growth rate) for Desmodesmus subspicatus was 1.71 mg/L (measured) for 2-ethylhexyl acrylate (BASF AG 2002), 5.28 mg/L (measured) for isobutyl acrylate (BASF AG 2002), and 14.6 mg/L (measured) for tert-butyl acrylate (BASF AG, 2002), respectively.

 

From three of the presented algae studies no observed effect concentrations could be derived. The NOEC for Desmodesmus subspicatus was determined to be 0.45 mg/L (measured) for 2-ethylhexyl acrylate, 0.82 mg/L (measured) for isobutyl acrylate, and 3.85 mg/L (measured) for tert-butyl acrylate, respectively.

 

Thus, EC50 values for freshwater algae were between 1.71 and 14.6 mg/L. The NOEC values ranged from 0.45 to 3.85 mg/L.

 

Based on the presented data, the most sensitive freshwater organism for the acrylic esters was Daphnia magna (EC50 = 1.3 mg/L).

 

In addition, there is a number of acute toxicity studies in marine organisms for two trophic levels (fish, invertebrates) available.

 

Marine fish

LC50 values in Cyprinodon variegatus were estimated to be 1.1 mg/L for methyl acrylate (BAMM, 1995), 2.0 mg/L (measured) for ethyl acrylate (BAMM 1995), and 2.1 mg/L (measured) for n-butyl acrylate (BAMM, 1996), respectively.

 

Thus, LC50 values for marine fish ranged from 1.1 to 2.1 mg/L.

 

Marine invertebrates

In an acute toxicity study with the seawater invertebrate Mysidopsis bahia (BAMM, 1996) an 96-hr LC50 of 1.6 mg/L based on mean measured concentrations was determined for methyl acrylate.

 

Long-term toxicity

Concerning long-term effects, a 21 -day chronic study with ethyl acrylate in Daphnia magna was conducted according to EPA guideline under flow-through conditions and with analytical monitoring (BAMM 1997). The NOEC for reproduction was 0.19 mg/L (measured).In addition, a 21-day Daphnia magna Reproduction Test was performed with n-butyl acrylate under semi-static conditions in accordance with OECD TG 211 (BASF SE, 2009). The effect concentrations were based on the time-weighted mean analytically detected concentrations: NOEC (reproduction) = 0.136 mg/L; LOEC (reproduction) = 0.457 mg/L. 

 

Aerobic microorganisms

The assessment of toxicity towards aerobic microorganisms was based mainly on data acquired with tert-butyl acrylate.

Effect values after 30 min exposure in a respiration inhibition test with domestic activated sludge according to OECD TG 209 were: EC20 = approx. 950 mg/L (BASF AG, 1993). Due to the considerable volatility of tert-butyl acrylate, this test which was conducted in an open system without analytical monitoring, has to be considered valid with restrictions. Also, a Pseudomonas respiration inhibition test was performed according to DIN 38412-27 (BASFSE, 1990). In this study, tert-butyl acrylate was dissolved in Tween 80 and incubated with Pseudomonas putida for 30 minutes with nominal test concentrations of 0 (control), 2500, 5000 and 10000 mg/L. As this test was performed in an open test system without analytical monitoring, the test is valid with restrictions. The EC10 was determined to be 8800 mg/L (nominal).

In accordance with the Guidance on information requirements and chemical safety assessment, Chapter R.10 (ECHA, May 2008), the tested concentration at which toxicity to the microbial inoculum can be ruled out can be considered as a NOEC for the toxicity to microorganisms. Therefore, the inhibition control in the CO2-Headspace Test conducted according to ISO 14593 (BASF SE, 2008) can be used as a NOEC = 30.5 mg/L.

In addition, there are valid experimental data from the other members of the acrylate category, e.g. the structurally related n-butyl acrylate. Effect values after 72 hrs exposure in a microbiological inhibition test with domestic activated sludge (BOD test) were: threshold inhibition concentration > 150 mg/L (BAMM 1995).

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