Predictive Models for Photoinduced Acute Toxicity of Polycyclic Aromatic Hydrocarbons to Daphnia Magna, Strauss (Cladocera, Crustacea)

Abstract

The photodynamic, actue toxicities of 20 polycyclic aromatic hydrocarbons (PAHs) to Duphniu mugnu were predicted by photophysical and physiochemical parameters. The photophysical parameters considered were lowest singlet energy, lowest triplet energy, singlet-triplet splitting energy and phosphorescence lifetime. The physiochemical parameters were first-and second-order connectivity indices and log P values. D. magna were exposed to aqueous solutions of each PAH such that equimolar concentrations in D. mugnu were achieved. The organisms and the PAHs were then exposed to 120 pW/cm2 UV-A and 25 pW/cm2 UV-B light. Mortality times (min) were recorded and the results reported as median lethal time (LT50). Potency factors (+) were calculated and used to rank the PAHs in terms of relative photodynamic toxicity. Some statistically relevant correlations between individual physical parameters and toxicity were observed. Linear, multiple regression models were poor predictors of photoinduced PAH toxicity. A curve-linear model was developed to predict photoinduced toxicity from triplet energy. Goodness-of-fit chi-square tests were performed and demonstrated that triplet energy was an effective predictor both of observed LT5O and of LT50 values adjusted to a constant PAH concentration. Toxicity data were also analyzed using discriminant functional analysis. A stepwise, canonical correlation parameter selection method separated the PAHs into three toxic categories by using triplet energy and phosphorescence lifetime as variables. This model, which classifies PAHs as very toxic, moderately toxic or nontoxic, was 100% accurate when the model developed from one set of PAHs was tested with a different set.

Photolysis, oxidation and subsequent toxicity of a mixture of polycyclic aromatic hydrocarbons in natural waters

“…As the irradiation continued the by-products along with the parent compound were further photolyzed and hence the overall toxicity decreased. Photoinduced toxicity is derived from two photochemical processes: photosensitization and photomodification [15,39,40]. During a photosensitization reaction intracellular singlet-state oxygen and other active oxygen species (ROS) are generated.…”

Photodegradation of phenanthrene in the presence of humic substances and hydrogen peroxide

“…PAHs are ubiquitous environmental contaminants (Cook and Pierce 1983;Evans 1993) which derived from a variety of anthropogenic sources involving mainly incomplete combustion of organic matter and by industries (Wild1990). It has been reported that many PAHs show a high toxic, carcinogenic, and mutagenic potential (White 1986;Pahlman and Pelkonen 1987;Depierre and Emster 1978;Newsted and Giesy 1987;Huang et al 1993). They are hazardous to ecosystems and human health.…”

UVA Light-Induced DNA Cleavage by Selected Polycyclic Aromatic Hydrocarbons

“…It is suggested that the phototoxicity of PAHs is due to light-induced generation of reactive oxygen species that further damage biomolecules (Newsted and Giesy, 1987;Pelletier et al, 1997;Swartz et al, 1997). The light-induced DNA cleavage results for the 14 tested PAHs here suggest that one possible phototoxicity source for these environmental contaminants is to cause DNA cleavage.…”