Evaluating Side Effects of Human Exposure to Noxious Agents

The anthropogenic environment as developed during the last 2 centuries rendered humanity vulnerable to a large number of environmentally noxious agents to which it had never been exposed. These agents, from their initial introduction into the ecosystem, directly or indirectly, continuously exert their effect on both living and nonliving systems. The result of this exposure will be evaluated by future generations. Over their evolutionary process, living systems have developed mechanisms to encounter naturally existing noxious conditions. These mechanisms gradually were developed in a way to protect life and assure its future evolution. Technological development over the last 2 centuries posed a serious threat to the evolutionary process of all living systems by introducing new and unknown noxious agents. These agents exert their effect either on biochemical pathways or on the DNA content of organisms. Regardless their target in living systems, they can be toxic, mutagenic, or carcinogenic. Humans are exposed to these agents either consciously or unconsciously. Conscious exposure occurs either occupationally or in lifestyle and can be controlled, while unconscious exposure is very dangerous. Electromagnetic radiation as well as chemicals used in industry, agriculture, services, food processing, or even for research and medical practice are among noxious agents introduced by humans. Human activities determine the rate by which these agents are introduced into the global ecosystem. Some of them have a short half-life, being naturally degraded in the atmosphere, ground, or water, while others are reasonably stable, exerting their side effects over long periods and areas. In addition, a considerable number of these agents exert their undesirable effect as products per se, while some of their degradation products are not considered noxious. However, a number of such agents are naturally degraded into byproducts that are more or less dangerous. Such byproducts sometimes are stable over long periods, can be accumulated in the ground or pass through it to the underground water pools, transmitting their action over long distances and periods. The present special issue is devoted to the various cytogenetic tests by which scientists try to elucidate the problem of human exposure to such noxious agents, as they confront them, consciously or unconsciously, in daily life. Conventional and sophisticated techniques are used nowadays. The cytogenetic techniques of choice for side effect evaluation are the micronucleus test (MN), the comet assay or single cell gel electrophoresis (CA or SCGE) test, the sister chromatid exchange (SCE), and the premature chromosome condensation (PCC) technique. In the meantime, combinations of various microscopic and molecular techniques are used for the study of the molecular events that result in the induced DNA damage from such agents. The micronucleus test, initially introduced by Heddle[1] for the study of chromosome damage, became an established technique for the evaluation of noxious agents side effects by Fenech and Morley[2]. Noxious agents exert either aneugenic or clastogenic effects. In aneugenic action, they