Ethylbenzene

Long-term toxicity to fish

Description of key information

No long-term toxicity test data were available with fish for ethylbenzene.

Additional information

A chronic fish toxicity study for ethylbenzene is not available. However there is a large amount of supporting evidence which suggests that the value is predictable, and that testing is not strictly required.

 

Ethylbenzene, based on its structure, is expected to exhibit toxicity through a non-polar narcotic mode of action (Verhaar et al., 1992). This suggests that the toxicity between the three aquatic trophic levels (fish, daphnia and algae) is not expected to vary significantly. Acute toxicity data are available which supports this assumption and, of the acute toxicity data available, fish were found to be the least sensitive trophic level (most sensitive LC50 = 4.2 mg/L, for Oncorhynchus mykiss, compared to EC50s of 1.8, 3.2 and 3.6 mg/L for Daphnia magna, Ceriodaphnia dubia and Selenastrum capricornutum, respectively).

 

Chronic toxicity data are available for invertebrates (NOEC = 1 mg/L, Ceriodaphnia dubia) and algae (NOEC = 3.4 mg/L,Selenastrum capricornutum). There is little variation of toxicity between both the chronic and acute toxicity data and the two chronic endpoints of these species, representing two trophic levels.

Chronic toxicity has also been predicted using a QSAR (Nabholz et al., 2009) and shows a good correlation with the measured data. The predicted 30-day ChV (chronic value) endpoint for fish is 1.13 mg/L, which lies within the range of the two measured chronic toxicity values for invertebrates and algae. The chronic endpoints for invertebrates and algae have also been predicted with a high degree of accuracy (0.908 and 2.242 mg/L, respectively).

 

Finally, acute:chronic ratios (ACRs) for substances with non-polar narcotic modes of action have generally been found to be low. An average ACR of these substances for studies mainly conducted on invertebrates was found to be 2.58 (Roex et al., 2000). An ACR calculated for ethylbenzene was 1.91. The chronic toxicity of ethylbenzene to fish, predicted using this ACR is 2.20 mg/L. It was noted that ACRs for fish were generally more variable than those for invertebrates, and hence less reliable. The 50^thand 95^thpercentile of ACRs for a range of non-polar narcotic substances which were calculated for a mixture of invertebrates and fish were 4.10 and 17.0, respectively (ECETOC, 2003). Toluene – a substance similar in structure to ethylbenzene – had an ACR of 8.1, based on 11 acute toxicity results and two chronic toxicity results. Given that the ACR of ethylbenzene for invertebrates was found to be lower than the average, and that a structurally similar substance had an ACR significantly lower than the 95^thpercentile of ACRs for a range of substances and species, it can be assumed that the ACR of ethylbenzene for fish will be lower than this 95^thpercentile, and an absolute worst case value for chronic fish toxicity can be calculated to be 0.25 mg/L.

 

Therefore, the testing of this endpoint is not scientifically necessary as there is strong evidence to suggest that chronic toxicity to fish is predictable and will lie in the range of 0.25-3.4 mg/L.

 

References

 

Verhaar HJM, Van Leeuwen CJ, Hermens JLM. 1992. Classifying Environmental Pollutants. Chemosphere, 25 (4) 471-391.

 

Nabholz V, Mayo-Bean K. 2009.ECOSAR v1.00, EPIWIN v4.0, U.S. Environmental Protection Agency.

 

Roex EWM, Van Gestel CAM, Van Wezel AP, Van Straalen NM. 2000.Ratios between Acute Aquatic Toxicity and Effects on Population Growth Rates in Relation to Toxicant Mode of Action. Env. Tox. and Chem. 19 (3) 685-693.

 

ECETOC. 2003. Technical Report Number 91. ECETOC