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ABSTRACT: An urgent need exists for incorporating heterocyclic compounds and (bio)transformation products in ecotoxicological test schemes and risk assessment of polycyclic aromatic compounds (PACs). The aim of the present study therefore was to determine the chronic effects of (heterocyclic) PACs on two terrestrial invertebrates, the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus. The effects of 11 PACs were determined in chronic experiments using reproduction and survival as endpoints. The results demonstrated that as far as narcosis-induced mortality is concerned, effects of both homocyclic and heterocyclic PACs are well described by the relationship between estimated pore-water 50% lethal concentrations and log Kow. In contrast, specific effects on reproduction varied between species and between compounds as closely related as isomers, showing up as deviations from the relationship between pore-water 50% effect concentrations and log Kow. These unpredictable specific effects on reproduction force one to test the toxicity of these PACs to populations of soil invertebrates to obtain reliable effect concentrations for use in risk assessment of PACs.
Environmental Toxicology and Chemistry 12/2009; 25(9):2423 - 2431. · 2.81 Impact Factor
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ABSTRACT: Adverse effects of azaarenes on emergence and mouthpart development of the midge Chironomus riparius were analyzed using six closely related three-ringed isomers and metabolites. Effects on growth rate were examined by comparing the average day of emergence of exposed midges with that of controls. Fluctuating asymmetry (FA) in the pecten epipharyngis was examined as a measure of developmental abnormality. Delayed emergence was found at concentrations as low as 2% of the acute LC50, so emergence day appears to be a useful sensitive parameter to quantify life cycle effects. No differences in FA were found between exposed and control larvae, although, in other studies, all compounds have been proven to be genotoxic. The differences in the genotoxic and FA-inducing properties of these compounds indicate that different mechanisms are involved in expressing these adverse effects. This study also illustrates that the choice of the morphological parameter strongly influences the results of developmental disturbance analyses and thus the risk qualification of a potentially hazardous compound.
Environmental Toxicology and Chemistry 11/2009; 18(8):1829 - 1834. · 2.81 Impact Factor
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ABSTRACT: Regarding impact on ecological soil functioning, metal pollution is often considered a constant factor for certain sampling sites. However, especially bioavailable concentrations may differ in space and time. This aspect was investigated on four sites along a metal-polluted river, differing in soil characteristics and metal concentrations. Every four weeks earthworm densities, soil characteristics, and metal concentrations in soil and earthworms were determined. Earthworm biomass and density fluctuated in time and increased with increasing metal contamination, indicating the presence of compensating factors. Multivariate analysis suggested organic matter and moisture content to be the main factors explaining earthworm biomass. Metal concentrations in the earthworms increased with increasing total or 0.01M CaCl(2) extractable soil concentrations, but no time-related trends were seen. Cadmium concentrations in the earthworms exceeded background values, suggesting a potential risk. The neutral red retention biomarker assay, however, did not show any signs of metal stress in the earthworms.
Environmental Pollution 09/2007; 148(3):824-32. · 3.75 Impact Factor
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ABSTRACT: An urgent need exists for incorporating heterocyclic compounds and (bio)transformation products in ecotoxicological test schemes and risk assessment of polycyclic aromatic compounds (PACs). The aim of the present study therefore was to determine the chronic effects of (heterocyclic) PACs on two terrestrial invertebrates, the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus. The effects of 11 PACs were determined in chronic experiments using reproduction and survival as endpoints. The results demonstrated that as far as narcosis-induced mortality is concerned, effects of both homocyclic and heterocyclic PACs are well described by the relationship between estimated pore-water 50% lethal concentrations and log Kow. In contrast, specific effects on reproduction varied between species and between compounds as closely related as isomers, showing up as deviations from the relationship between pore-water 50% effect concentrations and log Kow. These unpredictable specific effects on reproduction force one to test the toxicity of these PACs to populations of soil invertebrates to obtain reliable effect concentrations for use in risk assessment of PACs.
Environmental Toxicology and Chemistry 10/2006; 25(9):2423-31. · 2.81 Impact Factor
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ABSTRACT: Heterocyclic compounds by far outnumber the homocyclic PAHs. In addition, they are often more soluble in water, which may imply a greater biological significance of these heterocycles. Yet, most research focuses on the homocyclics, based on the implicit assumption that the mostly higher concentration of the homocyclics rank these compounds as priority compounds. This review critically examines the available evidence and poses questions on the biological activity and environmental risk of one small group of heterocyclics, the azaarenes, which contain one nitrogen atom in one of the aromatic rings. In different sections, the biotransformation and different types of toxicity are discussed in comparison to those of homocyclic PAHs. The last section focuses on the implications for risk assessment of PAHs. Two- and three-ringed azaarenes can be relatively easily transformed by bacteria, fungi, invertebrates, and vertebrates. The presence of the N-moiety in the smaller azaarenes leads to metabolic routes that partly differ from those of the homoaromatic analogues. Major metabolic products of the azaarenes appear to be ketones and mono- or dihydroxylated azaarenes. Microorganisms can further degrade these into multiple oxygen-containing compounds or they can open up the aza-containing aromatic ring and fully metabolize the products. Fungi and vertebrates were shown to produce the mutagenic dihydrodiol metabolites. The metabolism of the larger azaarenes in vertebrates proceeds analogous to homoaromatic PAH, because in these larger molecules the N-moiety has less influence. Transformation of the larger azaarenes by microorganisms proceeds much slower if occurring at all. Direct toxicity data of azaarenes are mostly restricted to the effects of acridine and quinoline on a relatively small number of species. From this limited set it becomes clear that differences between species are relatively small. As with homocyclic PAHs, toxicity generally increases with increasing number of rings, and baseline toxicity models based on homocyclic PAHs do apply. Toxicity differences between isomers indicate that azaarene toxicity cannot be explained by molecular size-related parameters alone, indicating that electronic forces may be important as well. Considering chronic toxicity it becomes clear that the often-used acute-to-chronic-ratios often underestimate specific chronic toxicity, even within the very limited set of chronic data available. In contrast with homocyclic PAHs, photodegradation of azaarenes shows the same degradation products as biological transformation involving monooxygenases. In general, as for homocyclic PAHs, the degree of phototoxicity is related to the UV absorption characteristics of the azaarenes, which makes it possible to apply the QSAR models developed for homocyclic PAHs to azaarenes as well. Recent research on algae showed that UV-A is the main cause of photoenhanced toxicity. Together with the fact that in the water column UV-B is almost absent, this clearly demonstrates the relevance of phototoxicity in the field. Mutagenicity of azaarenes generally proceeds through similar pathways as in homocyclic PAHs, with bay region diol epoxides as major genotoxic metabolites. The N-moiety can, however, result in differences in genotoxic activities between isomers. Carcinogenicity of azaarenes in mammals is generally restricted to four-ringed and larger structures, and mechanisms leading to cancer are similar to those of homocyclic aromatics. An exception to this general pattern is quinoline, which has been shown to induce liver cancer. The present risk assessment for PAHs is solely based on homocyclic PAHs. Yet, from the present review it becomes clear that this approach fails to protect against a vast number of heterocyclic compounds and biotransformation products that may exhibit stronger or other toxic effects than their homocyclic analogues. Therefore, incorporating the role of heterocyclic compounds and their metabolism appears to be a necessity for a reliable risk assessment for polycyclic aromatic compounds. In addition, reliable long-term protection against PAHs demands data on chronic toxicity, including teratogenicity, both for homocyclic as for heterocyclic compounds.
Reviews of environmental contamination and toxicology 02/2002; 173:39-83. · 3.45 Impact Factor
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ABSTRACT: Regarding impact on ecological soil functioning, metal pollution is often considered a constant factor for certain sampling sites. However, especially bioavailable concentrations may differ in space and time. This aspect was investigated on four sites along a metal-polluted river, differing in soil characteristics and metal concentrations. Every four weeks earthworm densities, soil characteristics, and metal concentrations in soil and earthworms were determined. Earthworm biomass and density fluctuated in time and increased with increasing metal contamination, indicating the presence of compensating factors. Multivariate analysis suggested organic matter and moisture content to be the main factors explaining earthworm biomass. Metal concentrations in the earthworms increased with increasing total or 0.01 M CaCl2 extractable soil concentrations, but no time-related trends were seen. Cadmium concentrations in the earthworms exceeded background values, suggesting a potential risk. The neutral red retention biomarker assay, however, did not show any signs of metal stress in the earthworms.
Environmental Pollution.
