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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

No algal toxicity test results were available for DPnB.  Endpoints were generated using QSARs to predict the acute toxicity to green algae.  

Key value for chemical safety assessment

EC50 for freshwater algae:
519 mg/L

Additional information

A QSAR assessment of the algal toxicity of Dipropylene glycol n-butyl ether was performed. Algal toxicity was assessed in terms of the effect concentration at which growth 50% inhibition of algal growth is determined (ErC50). Prediction from two published QSARs for algal toxicity (Van Leeuwen et al. 1992 and ECOSAR 1.00 – Nabholz, V. and K. Mayo-Bean, 2008) for the unknown and 4 analogues were calculated and compared with experimental data. From this comparison it was concluded that toxicity is overestimated by ECOSAR 1.00 neutral organics module and slightly underestimated by van Leeuven et al (1992).  Therefore, preference was given to a linear regression of the experimental data of three analogues (PGnPE, TPnB and PnB) against calculated log Kow using KOWWIN v 1.67 which resulted in the following relationship:

ErC50(96hr) = -1.1824.Log Kow + 1.7717 [log (mmol/l)]

The effect concentration for Dipropylene glycol n-butyl ether predicted based on this relationship is 519 mg/l.  A previous QSAR is provided as supporting information. From this previous study the ECOSAR program module of EPIWIN (v0.99) predicted a Green Algae 96 -hr EC50 of 556 mg/L. The more recent QSAR is considered more reliable and conservative, therefore the EC50 value of 519 mg/L was chosen as the key endpoint.