5-ethylidene-8,9,10-trinorborn-2-ene

Endpoint summary

Additional information

ENB has been tested for aquatic toxicity in three trophic levels including fish, daphnia and algae. For acute toxicity, a 96hEC50 of 3.68 mg/L for algae (OECD TG 201, Selenastrum capricornutum by biomass), a 48hEC50 values of 7.3 mg/L for daphnid (OECD TG 202, Daphnia magna, immobilization), and for fish a 96hLC50 of 7.6 mg/L (Brachydanio rerio) were available. Algae appear to be marginally the most sensitive level, although since the EC50 by growth rate was 8.93mg/l, it can reasonably be deduced that within margins of experimental error, all trophic levels show similar levels of toxicity. This supports the reasonable conclusion that the toxicity is non specific and acts through non-polar narcosis. This is backed up by the results from a reliable QSAR which predict LC/EC50 values all within a factor of ~3 or less of the measured values (predictions are more conservative.) The QSAR also predicts that the EC/LC50's across the difference species are all within <50% of each other and that the chronic values are a factor of <10 of the LC50 values. The results from a bioaccumulation study in fish also back up these conclusions. These observations should be taken into account in identifying an appropriate assessment factor for the PNEC derivation. Chronic data is available for daphnia (21 day reproduction NOEC=1.51mg/l) and for algae (72 hr NOEC = 0.852mg/l). Toxicity to micro-organisms is lower than other aquatic species. The effect of test substance on the nitrifying activity of activated sewage sludge gave a 5-min EC50 of 150 mg/l. The No Observed Effect Concentration (NOEC) after 5-minutes exposure was 100 mg/l.