Assessment of toxicity using dehydrogenases activity and mathematical modeling.

Dehydrogenase activity is frequently used to assess the general condition of microorganisms in soil and activated sludge. Many studies have investigated the inhibition of dehydrogenase activity by various compounds, including heavy metal ions. However, the time after which the measurements are carried out is often chosen arbitrarily. Thus, it can be difficult to estimate how the toxic effects of compounds vary during the reaction and when the maximum of the effect would be reached. Hence, the aim of this study was to create simple and useful mathematical model describing changes in dehydrogenase activity during exposure to substances that inactivate enzymes. Our model is based on the Lagergrens pseudo-first-order equation, the rate of chemical reactions, enzyme activity, and inactivation and was created to describe short-term changes in dehydrogenase activity. The main assumption of our model is that toxic substances cause irreversible inactivation of enzyme units. The model is able to predict the maximum direct toxic effect (MDTE) and the time to reach this maximum (TMDTE). In order to validate our model, we present two examples: inactivation of dehydrogenase in microorganisms in soil and activated sludge. The model was applied successfully for cadmium and copper ions. Our results indicate that the predicted MDTE and TMDTE are more appropriate than EC50 and IC50 for toxicity assessments, except for long exposure times.

Chemical elimination of the harmful properties of asbestos from military facilities.

This work presents research on the neutralization of asbestos banned from military use and its conversion to usable products. The studies showed that asbestos can be decomposed by the use of phosphoric acid. The process proved very effective when the phosphoric acid concentration was 30%, the temperature was 90°C and the reaction time 60min. Contrary to the common asbestos treatment method that consists of landfilling, the proposed process ensures elimination of the harmful properties of this waste material and its transformation into inert substances. The obtained products include calcium phosphate, magnesium phosphate and silica. Chemical, microscopic and X-ray analyses proved that the products are free of harmful fibers and can be, in particular, utilized for fertilizers production. The obtained results may contribute to development of an asbestos utilization technique that fits well into the European waste policy, regulated by the EU waste management law.

Impact of military metallurgical plant wastes on the population's health risk.

This paper presents the results of water, soil and air analyses taken in the vicinity of a former ferrochromium metallurgical plant. In the past, the area was used for the disposal of waste materials containing smelter slag, dust and other waste products from the manufacture of ferrochromium alloys for the army. Recently, production was abandoned and a project aimed at the liquidation of the dump has been initiated. The project concentrates on the recovery of chromium remains and the utilization of the leftover material as a road construction aggregate. Based on the analyses of ground water, soil and air, a health risk caused by environmental pollution with chromium, especially with Cr(VI), was determined for residential and occupational scenarios. It was found that the level of chromium emissions to the environment constitutes a potential danger of toxic and carcinogenic cases in humans exposed to the emission in the affected area. An increased level in the hazard quotient has been observed in the case of occupational activities. As far as the mutagenic effects are concerned, the occupational inhalation exposure was found to be very high, which may raise extreme concern about carcinogenic risk.