Terphenyl, hydrogenated

Short-term toxicity to aquatic invertebrates

Description of key information

Several invertebrate studies are available for hydrogenated terphenyls. The lowest EC50 (48h) is 0.1 mg/L. However, the test reporting an EC50 (48h) > 1.34 mg/L is considered the most relevant and reliable study. For risk assessment purposes this result is taken into account. This conclusion is further supported by the long-term toxicity study performed with Daphnia magna.

Additional information

A number of tests evaluating the acute toxicity of hydrogenated terphenyls towards aquatic invertebrates are available, several of which are GLP compliant and conducted according to the standard OECD 202 or other generally accepted guidelines. Seven out of ten studies were performed with Terphenyl, hydrogenated (Forbis, 1979; Powel and Moser, 1996; Adams, 1979; Gledhill, 1984; Hoberg, 1984 a&b) as the test substance, while for the remaining three a test substance containing 40 % hydrogenated polyphenyls was used (= read-across since the substance contains a larger fraction of hydrogenated quaterphenyls in comparison to the primary test substance) (Renaudette, 1984; Monsanto report, 1980; Calvert, 1982). In all cases but one, the endpoint was mortality (the other endpoint being mobility). Species tested were in most cases Daphnia magna, although Chironomus tentans, Mysidopsis bahia, Gammarus fasciatus and Paratanytarsus parthenogenetica were used as well.

Based on the results reported in all these studies, no toxicity was observed up to water solubility levels (0.06 mg/L).

To summarize, only one test reported a measured exposure concentration: this limit test (at 1.34 mg/L Terphenyl, hydrogenated, measured concentration) indicated that the EC₅₀(48h) is > 1.34 mg/L (Powell and Moser, 1996). Otherwise, EC₅₀(48h) values for freshwater invertebrates reported for hydrogenated terphenyl ranged from 0.1 mg/L to > 1.5 mg/L (nominal concentrations). It should be noted that all tests, except the most recent one (EC50 > 1.34 mg/L), did not report measured concentrations, the tested concentrations were above the water solubility and a solvent was used. Additionally it was questioned in one of those older reports whether the observed toxicity really originated from the test substance or whether it was brought about by the development of a surface film. Tests conducted with the read-across substance containing 40 % hydrogenated polyphenyls generally indicated a higher level of toxicity with an EC₅₀(48h) value ranging from 0.011 to 0.52 mg/L. These test results were not taken into account due to the obvious difference in composition of the substance in comparison to Terphenyl, hydrogenated, the fact that also those tests all used a solvent and did not report measured concentrations. To conclude, although the lowest EC50 (48h) is 0.1 mg/L, the test reporting an EC50 (48h) > 1.34 mg/L is considered the most relevant and reliable study. For risk assessment purposes this result is taken into account. This is further supported by the observations made in the OECD211 study where a WAF approach was used. In that study a NOELR (21 days) of 1 mg/L was determined for the mortality endpoint. There results are not unexpected as the use of a solvent and/or dispersing agent could increase the bioavailability of certain constituents of the UVCB and influence the observed toxicity.