Synergistic Interaction of Detrimental Factors Can Intensify Disaster Consequences

Experimental data obtained for simultaneous action of ionizing radiation with different physical or chemical agents on various cellular systems evidence that the lesser the intensity of physical factor or the concentration of chemical agents, the smaller the temperature that has to be used to provide the highest or a definite level of synergistic interaction. On this basis, it is inferred that the synergism may take place at small intensities of harmful environmental factors existing in the biosphere and can intensify disaster consequences. Hence, the assessment of health or environmental risks both in normal and disaster conditions should take into account the synergistic interaction between harmful agents. INTRODUCTION Combined exposures are an essential feature of modern life. It is well known that almost all physical and a wide array of chemical harmful agents, both natural and 2 man made, are capable of interacting with each other in a synergistic manner when the final biological effect exceeds the sum of individual effects produced by interacting agents. Therefore any risk assessment must consider the question whether or not combined effects will influence the health outcome. Of all possible situations of the combined actions, long term exposure of living objects to low levels of the agents widely presented in the nature is especially important. However, the assessment of potential significance of synergistic interaction between adverse environmental factors acting together at the level of intensity and concentration found in biosphere is still an intriguing and unresolved problem. Real experiments with low intensities found in environmental and occupational settings are prone to large uncertainties. A feasible approach to this problem is to analyze the dependence of the efficiency of synergistic interaction on the intensity of agents used. Hypothetically, some possibilities could be realized. The case where synergism is decreasing with intensities of deleterious agents applied is unimportant. The same is true for the situation when a decrease in the intensity of one factor should be accompanied by an increase in the intensity of another to retain their synergistic interaction at the same level. The only possibility would be of great importance: if the lesser intensity of one of the agents is applied, then the smaller intensity of another agent should be employed for the display of the highest or a definite level of synergy. In such a case, it would be expected that even at low intensity environmental agents may, in principle, interact with each other in a synergistic manner and thereby to enhance their harmful action. The same is true for different kinds of local or national disaster resulting in an increase both in a number of harmful agents and their intensity. In this paper, we present conclusive evidence confirming these opportunities for various cellular systems and acting noxious agents.