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 -2. Fate and partitioning in aquatic environments.

Butylparaben and benzylparaben, used as preservatives mainly in cosmetic products, have recently been shown to be weakly estrogenic. Batch sunlight photolysis and river water biodegradation experiments were conducted to determine the persistence of these compounds in aquatic environments. As a result, benzylparaben was found to be moderately photodegradable whereas both n-butylparaben and i-butylparaben were highly stable against sunlight. Both benzylparaben and butylparabens were relatively biodegradable in the river water but the degradability was dependent on the sampling site and time. Batch sorption experiments were also conducted to determine the coefficients of sorption into river sediments and a model soil sample. The determined coefficients were slightly higher for benzylparaben than the two butylparabens and comparable to that of the natural estrogen 17beta-estradiol. The coefficients were also higher for sediment/soil with a higher organic content and the organic-carbon-based sorption coefficient (log K oc) shows a moderate linear correlation with the octanol-water partition coefficient (log K ow). These results suggest that hydrophobic interaction plays a predominant role in sorption at neutral pH.