The role of laboratory and field leaching tests in hazard identification for solid materials

The use of various in vitro toxicity assays for testing environmental solid samples is dependent on the availability of reliable methods for the sampling and pretreatment of the material. This study focuses on the evaluation of leaching behaviour as a first step in the context of the toxicity testing of solid environmental matter. Spent shale, from oil shale retorting, was chosen as a suitable example of deposited solid waste material. For the generation of leachate in the laboratory setting, a standard two-stage batch-leaching test was applied to the samples of technogenic waste. In the field, a new type of lysimeter, which does not disturb the surface, was used for in situ leachate collection. The chemical composition of water extracts was found to be different under field conditions, as compared with the laboratory experiments. Thus, the hazard identification of a solid technogenic waste by in vitro toxicological tests applied to laboratory leachates would not be the best solution. The content of hazardous ingredients could be underestimated if only laboratory tests are used. For risk assessment concerned with solid waste materials, the generation of leachate by using field lysimeters is recommended.     

Comparative fluorometric study of benzo(a)pyrene and aza-aromatic hydrocarbon penetration and metabolism kinetics in the skin of hairless mice.

The kinetics of penetration and metabolism of BaP, BACs, DB(a,h)ACs and DB(c,g)Cs in the skin of hairless mice was studied. The relative fluorescence intensities were measured during three hours after applying 10 nmoles of the compound to the interscapular region of the mice. By using a kinetical model which combines a non-steady diffusion of a hydrocarbon through the stratum corneum and the metabolic oxidation by epidermal cells, the rate constants for the two processes were calculated. It has been shown that B(a)AC, B(c)AC and 12-MB(a)AC penetrate into the skin and are oxidized by epidermal cells more efficiently than BaP. In contrast, alkyl-DB(a,h)ACs (except 14-MDB(a,h)AC) show a great stability in the mouse skin. The carcinogenic BaP, 7-MB(c)AC and DB(a,h)AC have average rates of elimination from the skin.