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Ecotoxicological information

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The ecotoxicity of C9 aromatics have been examined in a series of studies on fish, Daphnia and algae, as well as in microorganisms and birds. The most conservative results of aquatic studies showed C9 aromatics to be of moderate toxicity, with LC50 or EC50 values of 9.2 mg/L (fish), 3.2 mg/L (Daphnia), and 2.6-2.9 mg/L (for biomass and growth rate), respectively, of algae). All of these studies were conducted in Water Accommodated Fraction (WAF) studies because of the limited water solubility of C9 aromatic materials. In this methodology, different loadings of the substance are added to the test medium and equilibrium between the water and the hydrocarbons is achieved according to their specific water solubility. The hydrocarbon concentrations at equilibrium will be characteristic of the loading of the substance, and therefore toxicity values from WAF studies are expressed as effect loadings or lethal loadings (EL or LL), not as concentrations. These effect loadings are used to determine environmental classifications. The WAF methodology is widely accepted for the testing of complex hydrocarbon substances and other UVCBs, and it has been incorporated in different guidance documents, including the REACH guidance (see draft decision response letter in Section 13). A study conducted with microorganisms demonstrated no significant toxicity (EC50 >99 mg/L), indicating that there would not be inhibition or toxicity to sewage treatment plant microorganisms.

Acute Fish Toxicity:

Water accommodated fractions of hydrocarbons, C9, aromatics, produced a 96-hour LL50 value of 9.2 mg/L with rainbow trout, Oncorhynchus mykiss.

Chronic Fish Toxicity:

The hydrocarbons, C9, aromatics, estimated freshwater fish 28-day NOELR (No Observed Effect Loading Rate) value is 1.23 mg/l based on growth.

Acute Invertebrate Toxicity:

Water accommodated fractions of hydrocarbons, C9, aromatics, produced a 48-hour EL50 value of 3.2 mg/L with Daphnia magna.

Chronic Invertebrate Toxicity:

The hydrocarbons, C9,% aromatics, estimated freshwater invertebrate 21-day NOELR (No Observed Effect Loading Rate) value is 2.14mg/l based on reproduction.

Algal Toxicity:

Water accommodated fractions of hydrocarbons, C9, aromatics, produced 72-hour ELb50 and ELr50 values of 2.6 and 2.9 mg/L,respectively, with the alga,Pseudokirchnerella subcapitata.The lowest NOELR values come from a second study, 0.22 mg/L for biomass and growth rate.

Microorganisms Toxicity:

The hydrocarbons, C9, aromatics, estimated protozoan, Tetrahymena pyriformis, 48-hr EL50 value for this substance is 21.16 mg/L based on growth inhibition.