Long-term toxicity of five polycyclic aromatic hydrocarbons for the terrestrial isopods Oniscus asellus and Porcellio scaber

Polycyclic aromatic hydrocarbons (PAHs) are a common component of soil pollution, yet little is known of the ecotoxicological risks these compounds may pose to life in soil. This article reports the ecotoxicity of five PAHs for two terrestrial isopod species. Isopods were exposed to food contaminated with four different concentrations of either fluorene, phenanthrene, fluoranthene (up to 4 mu mol/g), benz[a]anthracene, or benzo[a]pyrene (up to 1.25 mu mol/g). Exposure of Porcellio scaber lasted 16 weeks, and no adverse effects on survival, growth, or total protein (only females tested) were observed in any of the treatments. A small but significant reduction in growth of Oniscus asellus was observed at 47 weeks of exposure to 0.125 mu mol benz[n]anthracene . g(-1) dry weight and 1.25 mu mol fluorene g(-1) dry weight and higher concentrations. A significant stimulation of the reproduction of O. asellus was observed in some of the phenanthrene, fluoranthene, benz[a]anthracene, and benzo[a]pyrene treatments; a larger proportion of the females were gravid, which resulted in a higher number of juveniles per female. Exposure did not significantly affect brood size, weight of the mother after release of the juveniles, or the survival of the juveniles upon starvation. Total protein content of females was significantly reduced at 0.4 mu mol fluorene g(-1) dry weight and higher concentrations. Growth and protein content of isopods is likely to be affected by PAH exposure only at highly contaminated sites. The ecological consequences of stimulated reproduction and possible DNA damage are poorly understood and require further attention because soil invertebrates may be exposed to PAHs over many generations.