Terphenyl, hydrogenated

Toxicity to aquatic algae and cyanobacteria

Description of key information

The calculated 96 hour EC50 based on cell number decrease was 56 ppm (oldest study). In the most recent study, performed with a WAF approach no effects were seen up to concentrations of 100 mg/L.

Additional information

Two studies on algae are available (Hollister, 1979; Weltens, 2010). In the most recent study, algae were exposed to water soluble fractions of hydrogenated terphenyl. The presence of hydrogenated terphenyl in these WAFs could be measured with HPLC when solutions were freshly prepared. This soluble fraction however disappeared during the exposure time both in filtered and unfiltered WAFs and it was not clear from the results how fast the test substance disappears. The initial presence of these soluble compounds in the WAFs however does not interfere with normal algal growth rate for WAFs produced with nominal concentrations up to 100 mg/L hydrogenated terphenyl. As no effects were seen in the test range, no effect values could be defined.

In the oldest phytotoxicity study (K2), the effect of exposure to hydrogenated terphenyls was also determined on the freshwater alga Selenastrum capricornutum (new name P. subcapitata).The basis of effect in that study was in vivo chlorophyll a (for all time points). After 96 hours, also cell numbers in exposed and control cultures were compared resulting in the calculation of EC₅₀.However, only nominal concentrations were reported (10, 32, 56, 100 and 320 mg/L). Based on the decrease of in vivo chlorophyll a, the estimated 24 hour EC₅₀was > 320 ppm, while the calculated 96 hour EC₅₀was 44 ppm with 95% confidence limits of 1 - 1586 ppm. The calculated 96 hour EC₅₀based on cell number decrease was 56 ppm with confidence limits of 4 -743 ppm. Due to the large confidence limits in this study, the reliability of this study is not regarded to be very high.