Algal growth inhibition of Chlorella pyrenoidosa by polar narcotic pollutants: toxic cell concentrations and QSAR modeling

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The effects of 11 polar narcotic pollutants (phenols, nitrobenzenes and anilines) on the algae Chlorella pyrenoidosa have been investigated in 72 h population growth inhibition tests. The lowest observed effect concentration and no-observed effect concentrations were determined. The partial effect concentrations were estimated (EC 1 0 and EC 5 0) by the Weibull function, and no-effect concentrations were determined by using the debtox program. In addition, for four of the chemicals, the internal cell concentrations yielding 10 and 50% growth inhibition were estimated from internal concentration–response curves. The toxic cell concentrations vary from 0.1 to 1.6 and from 0.5 to 17 mmol kg −1, for 10 and 50% inhibition, respectively. These values are in agreement with reported data for Selenastrum capricornutum (0.7–2.3 and 2–14 mmol kg −1, respectively). Finally, the determined (no-)effect concentrations have been used to construct quantitative structure–activity relationship models using hydrophobicity and hydrogen bonding capacity descriptors. The models indicate that toxicity increases with hydrophobicity, good hydrogen bonding donor capacity, and low hydrogen bonding acceptor capacity. The models can be interpreted based on the composition of biomembranes, which are supposed to be the target of narcotic pollutants.