reaction mass of ethylbenzene and m-xylene and p-xylene

Toxicity to aquatic algae and cyanobacteria

Description of key information

The studies by Galassi (1988) were chosen as the key studies on the basis that they were conducted according to OECD standard guidelines, analytical monitoring was performed and appropriate modifications for volatile compounds were made. The reported 72 hours EC50 results from these studies for the different isomers and ethylbenzene for Selenastrum capricornutum had an average of 4.7 mg/L.

The lowest result listed in the Draft Screening Assessment Report (Environment Canada 2014) for algal toxicity was a 48 hour EC50 of 1.3 mg/L for Ethylbenzene.

The lowest long-term result was reported by Oldersma et al (2004) for p-xylene with a 72 -hour NOEC of 0.44 mg/L.

The estimated EL50 values from TLM QSAR were 4.831 - 6.129 mg/L. The estimated NOELR values from TLM QSAR were 0.925 -1.174 mg/L.

The lowest values for EC50 and NOEC were used in chemical safety assessment, which were from Environment Canada 2014 (ethylbenzene) and Oldersma 2004 (p-xylene) respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.3 mg/L

EC10 or NOEC for freshwater algae:

0.44 mg/L

Additional information

Data are available on the ecotoxicity of each of the xylene isomers and ethylbenzene to algae. The studies by Galassi et al (1988) and Oldersma (2004) followed OECD 201, whilst Herman et al (1990) used a non-standard method. All studies included analytical confirmation of the exposure concentrations.

The lowest results listed in the EU RAR (ECB 2007) for the toxicity of ethylbenzene to algae are a 72 hour NOEC of 3.4 mg/L. The study is considered by the ECB to be reliable, and although results for 96 hours are also presented in the report, the algae were not in an exponential growth phase and therefore the results have not been used for effects assessment. The lowest results listed in the Draft Screening Assessment Report (Environment Canada 2014) for algal toxicity are a 48 hour EC50 of 1.3 mg/L for ethylbenzene.

The EC50 results reported from these studies for the different isomers and ethylbenzene are very similar, with a range of 1.3 - 4.9 mg/L. The lowest long-term result was reported by Oldersma et al (2004) for p-xylene with a NOEC of 0.44 mg/L. The lowest short-term result was reported in the EU Risk Assessment Report (ECB 2007) for ethylbenzene.

A TLM-EqP modeling framework was used to support values derived experimentally and are presented as supporting studies.

The estimated EL50 values from TLM QSAR were 4.831 - 6.129 mg/L, and the estimated NOELR values from TLM QSAR were 0.925 - 1.174 mg/L.