Photoinduced toxicity of polycyclic aromatic hydrocarbons to Daphnia magna: ultraviolet-mediated effects and the toxicity of polycyclic aromatic hydrocarbon photoproducts.
ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants known for their photoinduced toxicity. This toxicity may occur through two mechanisms: Photosensitization, and photomodification. Photosensitization generally leads to the production of singlet oxygen, a reactive oxygen species that is highly damaging to biological molecules. Photomodification of PAHs, usually via oxidation, results in the formation of new compounds and can occur under environmentally relevant levels of actinic radiation. The toxicities of 16 intact PAHs to Daphnia magna were assessed under two ultraviolet radiation conditions. The toxicity of intact PAHs generally increased in the presence of full-spectrum simulated solar radiation relative to that in the presence of visible light plus ultraviolet A only. Despite the knowledge of a bipartite mechanism of phototoxicity that includes photosensitization and photomodification, few studies have examined the effects of PAH photoproducts on animals. To expand the existing data, 14 PAH photoproducts (oxy-PAHs) also were assayed, most of which were highly toxic without further photomodification. Two photoproducts of benzo[a]pyrene, 1,6- and 3,6-benzo[a]pyrenequinone, were the most toxic compounds tested, followed closely by benz[a]anthraquinone. Each of these three compounds had a median effective concentration in the low nanomolar range. The data presented highlight the effects of ultraviolet radiation on mediating PAH toxicity and the need to analyze absorption spectra of contaminants in the prediction of photoinduced toxicity. The importance of the role of photomodification also is stressed, because several oxy-PAHs, an unregulated group of contaminants, were highly toxic to D. magna, a key bioindicator species in aquatic ecosystems.
Chapter: Concentrations of Hydrophobic Organic Pollutants in U.S. Wastewater Treatment Plants and in Receiving Surface Waters Modeled from EPA Biosolids Monitoring Data[show abstract] [hide abstract]
ABSTRACT: Organic microcontaminants such as pharmaceuticals and personal care products (PPCPs) are currently not regulated with regards to wastewater treatment removal. To provide a basis for risk assessment, the U.S. Environmental Protection Agency (EPA) conducted a nationwide sampling campaign at seventy-four publicly owned treatment works, to assess contamination of biosolids with 145 different pollutants. However, a similar nationwide study of PPCPs contained in treated effluent of such a large number of wastewater treatment plants has never been conducted. In this study, a published empirical model was modified, and applied, to estimate from the biosolids concentrations reported by the EPA, the concentrations in raw and treated wastewater of pharmaceuticals and other organic contaminants. Target chemicals included eight organic compounds: (benzo(a)pyrene, beta-estradiol-3-benzoate, fluoranthene, miconazole, norgestimate, pyrene, triclocarban and triclosan. These compounds were selected based on the hydrophobicity range for which the model previously had been validated. The results of the mass loading estimations are compared to measured concentrations in treatment plant influent and effluent and also are put in relation to contaminant concentrations found in effluent receiving U.S. surface waters. Potential impacts on sensitive environmental receptors as well as potentially effective treatment methods for wastewater are identified and discussed. The removal efficiencies predicted by the model ranged from ≥13% for triclosan to ≥82% for benzo(a)pyrene. Modeled contaminant concentrations in treatment plant influent ranged from 0.025 to 12 µg/L whereas modeled contaminant concentrations in effluent ranged from 0.0062 to 10 µg/L. A comparison of predicted and observed removal efficiencies for triclosan and triclocarban indicated that the model predictions are conservative in nature and comparable to actual measurements made at sewage treatment plants. This study produced the first concentration estimates for beta-estradiol-3-benzoate, miconazole, and norgestimate in surface waters and identified important information gaps concerning ambient concentrations of microcontaminants and associated ecotoxicological effects.01/2010: pages 421-436; , ISBN: 084122496X
Article: Sources, Fate, and Toxic Hazards of Oxygenated Polycyclic Aromatic Hydrocarbons (PAHs) at PAH- contaminated SitesAMBIO A Journal of the Human Environment 01/2009; · 2.03 Impact Factor