Aquatic toxicity and ecological risk assessment of seven parabens: Individual and additive approach.

In the present study, aquatic concentrations of seven parabens were determined in urban streams highly affected by treated or untreated domestic sewage in Tokushima and Osaka, Japan. The detected highest concentrations were 670, 207, and 163ngl(-1) for methylparaben, n-propylparaben, and n-butylparaben, respectively in sampling sites with watershed area of no sewer system in Tokushima. Conventional acute/chronic toxicity tests were conducted using medaka (Oryzias latipes), Daphnia magna, and Psuedokirchneriella subcapitata for four parabens, which was consistent with our previous study on three parabens, n-butylparaben, i-butylparaben, and benzylparaben. The aquatic toxicity on fish, daphnia, and algae was weaker for the parabens with a shorter alkyl chain than those with a longer alkyl chain as predicted by their hydrophobicity. Medaka vitellogenin assays and DNA microarray analysis were carried out for methylparaben and found induction of significant vitellogenin in male medaka at 630µgl(-1) of methylparaben, while the expression levels of genes encoding proteins such as choriogenin and vitellogenin increased for concentrations at 10µgl(-1) of methylparaben. Measured environmental concentrations (MECs) of seven parabens in Tokushima and Osaka were divided by predicted no effect concentrations (PNECs) and hazard quotient (MEC/PNEC) was determined for individual parabens. The MEC/PNEC was highest for n-propylparaben and was 0.010 followed by n-butylparaben (max. of 0.0086) and methylparaben (max. of 0.0042). The sum of the MEC/PNEC for the seven parabens was 0.0049. Equivalence factors were assigned for each paraben on the basis of the toxicity of n-butylparaben for each species, and n-butylparaben equivalence was calculated for the measured environmental concentrations. The MEC/PNEC approach was also conducted for the n-butylparaben-based equivalence values. The maximum MEC/PNEC was 0.018, which is lower than the trigger level for further detailed study such as large-scale monitoring for chronic toxicity tests including full-life cycle tests for fish.

Preliminary ecological risk assessment of butylparaben and benzylparaben -1. Removal efficiency in wastewater treatment, acute/chronic toxicity for aquatic organisms, and effects on medaka gene expression.

Butylparaben and benzylparaben, used as preservatives mainly in cosmetic products, have recently been found to be weakly estrogenic. Batch activated-sludge treatment and batch chlorination were carried out to roughly determine the removal efficiency of a wastewater treatment plant. Combining the removal efficiency with the estimated annual consumption and the unaltered excretion ratio, the maximum predicted environmental concentration (PEC) was estimated. Conventional acute/chronic toxicity tests were conducted using Japanese medaka (Oryzias latipes), daphnia (Daphnia magna), and green algae (Pseudokirchneriella subcapitata) for n-butylparaben, i-butylparaben, and benzylparaben. Medaka vitellogenin assays were also conducted for the three compounds and DNA microarray analysis was carried out to examine the effects of benzylparaben on gene expression. The plasma vitellogenin concentration of male medaka increased for concentrations of 200, 100, and 100 microg L(-1) n-butylparaben, i-butylparaben, and benzylparaben for 14 days, respectively, while the expression levels of genes encoding proteins such as p53, cytochrome P450 3A40, and choriogenin-L increased for concentrations higher than 4 microg L(-1) of benzylparaben. Furthermore, the predicted no-effect concentration (PNEC) was calculated using the lethal or effect concentration 50 (LC50 or EC50) values and no-effect concentrations (NOECs) obtained in the toxicity tests for these compounds. The maximum concentrations found in the aquatic environment or sewage effluent (MEC eff) were used to carry out preliminary environmental risk assessment. The calculated MEC/PNEC ratio suggests the necessity of further study such as a more detailed large-scale monitoring and chronic toxicity tests including reproduction inhibition and endocrine disruption.