Photostability and phytotoxicity of selected sunscreen agents and their degradation mixtures in water |
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Authors: | Rosario Rodil Monika Moeder Rolf Altenburger and Mechthild Schmitt-Jansen |
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Institution: | (1) Department of Analytical Chemistry, Nutrition and Food Science, IIAA-Institute for Food Analysis and Research, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain;(2) Department of Analytical Chemistry, Helmholtz Centre for Environmental Research, UFZ, Permoserstra?e 15, 04318 Leipzig, Germany;(3) Department Bioanalytical Ecotoxicology, Helmholtz Centre for Environmental Research, UFZ, Permoserstra?e 15, 04318 Leipzig, Germany; |
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Abstract: | The study on the photostability of six UV filters in aqueous solution was combined with investigations on the phytotoxicity
of the produced degradation mixtures. During the exposure to artificial sunlight over 72 h, the degradation of three of the
UV filters evaluated was observed with half-lives between 20 and 59 h. The structural changes of iso-amylmethoxy-cinnamate
(IAMC), ethylhexyl-methoxy-cinnamate (EHMC), and 4-methylbenzyliden camphor (4-MBC) occurred during irradiation were consistent
with isomerisation and polymerization (IAMC and EHMC) whereas 2-ethylhexyl-4-(dimethylamino)benzoate (OD-PABA) was degraded.
The analysis of the UV filters and their degradation products was performed by stir bar sorptive extraction (SBSE) followed
by thermodesorption–gas chromatography–mass spectrometry (TD-GC-MS) or liquid desorption–liquid chromatography–mass spectrometry
(LD-LC-MS). The phytotoxicological potential of the UV filters was examined in vitro by evaluating reproduction inhibition
of the chlorophyte microalgae Scenedesmus vacuolatus. Excess toxicity was calculated by comparing experimental derived median efficiencies after log-logistic modeling to predict
effects assuming narcotic mode of action. Benzophenone-3 (BP-3) showed 43-fold higher toxicity than theoretically predicted
and a more specific mode of action was assumed. The other UV filters tested indicated toxicity in the range of modeled narcosis.
For IAMC, EHMC, and OD-PABA the phytotoxicity of their photodegradation mixtures was followed over time. Phytotoxicity decreased
directly with the reduction of the parent substance from the solution. Five of the tested UV filters do not represent a risk
at least for algae. Octocrylen and 4-MBC were found to be photostable but few toxic to algae. EHMC, IAMC, and OD-PABA were
fast degraded during UV radiation and the phytotoxicity of the corresponding degradation mixtures was low and decreased onward
during exposure. Thus, for the UV filters studied, it could be confirmed that sunlight can account noticeably for decontamination
and detoxification of contaminated water. However, due to its potential accumulation in combination with a specific mode of
action, BP-3 may imply probable environmental risks at least to algae. This study emphasizes the need of a combined chemical
and toxicological evaluation for a reliable risk assessment concerning degradation processes exemplified here for UV-protecting
agents. |
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