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The substance ’Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised’ (NAF-AO) [EC no. 701-299-7] is a UVCB substance and consists of various constituents that can be divided into three component groups. These are dimers, trimers, and oligomers (n ≥ 4) formed during the production process from the monomeric starting material ‘C8-10 aromatic hydrocarbon fraction’.

The aquatic toxicity was tested in short-term toxicity tests with fish and aquatic invertebrates (daphnia) and in toxicity tests with algae and with aquatic microorganisms (respiratory inhibition). Test materials were different types (technical products) of NAF-AO (short-term test with aquatic invertebrates (daphnia) and toxicity test with algae). In addition, the structure related substance ‘Oligomerisation and alkylation reaction products of 2-phenylpropene and phenol’ (OAPP) [EC no. 700-960-7] was used as supporting substance (source substance) for read-across (short-term toxicity to fish and toxicity to microorganisms). OAPP is also a complex UVCB substance and contains except other components also two of the component groups that are present in NAF-AO (dimers and trimers).

Due to the complex composition and variable but low/very low solubility of its components, water solubility of both substances is not clearly defined. Depending on the quantity used, concentration of material dissolved in saturated water samples is variable. Therefore, water accommodated fractions (WAFs) have been used in aquatic toxicity testing. Thus, results of the aquatic toxicity tests are given as loadings (LL/EL50, LL/EL0, NOELR).

Short-term toxicity tests with fish have been carried out with OAPP as test substance. The LL50 (LL = lethal loading) was determined to be 25.8 mg/L.

Short-term Daphnia tests were performed with three different technical products of NAF-AO (Novares L 100, L 800, and TC 10). The daphnia 48-h EL50 values range from 54 mg/L to > 1000 mg/L.

In the toxicity test to aquatic algae, two technical products of NAF-AO were used as test materials. Novares L 100 produced no adverse effects on algal growth (EL50 >100 mg/L, NOELR = 100 mg/L) in a limit test. The same result was obtained in a limit test with the test material Novares TL 10.

Toxicity to aqueous microorganisms was tested with OAPP as test substance. In an activated sludge respiratory inhibition test, no adverse effects on the respiratory rate of sludge microorganisms was observed (limit test: EL50 > 100 mg/L, NOELR = 100 mg/L).

The highest toxicity to aquatic organism was determined with OAPP as test substance in the short-term toxicity test to fish (EL50 = 25.8 mg/L). This result is adopted for the chemical safety assessment and the derivation of PNECs of NAF-AO.