Professor Athanassios Kungolos from the Department of Development and Planning of the University of Thessaly in Greece has given a course of lecture at Ashurst Lodge on “Toxicology and Eco-toxicology”.
Athanassios started by explaining that Eco-toxicology examines the occurrence of chemicals and other agents in ecosystems, in terms of the effect that they may cause on live organisms. Eco-toxicology is a valuable tool for the effective evaluation of the environmental risks arising from the release of chemicals into aquatic and terrestrial environment.
Various inorganic and organic substances (when present in sufficiently elevated concentrations), released into the environment through anthropogenic activities can exhibit adverse effect on biological processes.
In eco-toxicological assessments (bioassays) live organisms are exposed to the materials of concern and the effect in terms of mortality, reproduction or growth inhibition is measured as an end point. The common test species used for the toxicity assessments include bacteria, micro algae, protozoan, rotifers, crustaceans, fishes and plants. In the past few years the use of bioassays had the seriously drawback of the need of continuous culturing/availability and maintenance of stocks of live test organisms in good health and in sufficient numbers, but a relatively new technique has been developed, from which life test organism can easily be obtained on demand to perform the toxicity tests.
Single chemicals almost never occur alone in aquatic and terrestrial environment and, the ultimate toxicity is not the sum of the individual toxicities. Phenomena such as e.g. bioavailability, synergistic or antagonistic effects indeed always dictate the ultimate hazard of the mixtures. Several methods have been developed predicting the theoretically expected effect when two or more chemicals are applied together on an organism.
A single toxicity test cannot tell how other important groups of biota may be affected by exposure to the same chemical(s). Toxic effects are indeed ‘species specific’ as well as ‘chemical specific’. It is thus necessary, when attempting to estimate the hazard of compounds or products released in the environment to use a battery of tests with species representative of the different links in the trophic chain.
QSAR (Quantitative Structure-Activity Relationships) are used to refer to a process in which the structures of a set of compounds are quantified and then trained against their numerical values of the biological activity or physical property. The result is a mathematical model that can be used to predict the activity or property value of compounds. The eco-toxicological approach is to have a series of bioassays test, including:
- Acute (short term) toxicology tests
- Chronic toxicity tests
- Reproduction tests
- Bioaccumulation studies
- Genotoxicity tests
Chemical analysis present the causes but the effects are only visible through toxicology tests.
Athanassios referred also to the need to balance realistic tests with financial constraints. Several cases studies were presented during the lectures demonstrating the effects of toxic compounds.
The series of lectures were followed with great interest and stimulated a series of lively discussions.
Wessex Institute