Application of Molecular Topology for the Estimation of Physical Data for Environmental Chemicals

The chemical industry has grown enormously in recent decades. It provides us with numerous vital chemicals (fuels, antibiotics and other drugs, plastics, pesticides, fertilizers, etc.) without which our society cannot survive and preserve its present life style and high living standards. Many of these substances have little or no adverse environmental effects, but some may be harmful to human health and the natural environment. Usually these effects only become apparent after wide and prolonged usage and at that point authorities introduce control measures. Clearly, there is a need for an effective evaluation and testing program to identify, before their use, those chemicals or classes of chemicals that present a potential environmental hazard. Such evaluation procedure should trace the fate of chemicals from discharge and dispersal to subsequent effects on biota. The ecotoxicological profile of a chemical is based on a sequence of interactions and effects controlled by its physical, chemical, and biological properties. At the first stage, a chemical released into the environment is subject to physical distribution between the atmosphere (air), water, soils, and sediment depending on its physico-chemical properties. At the same time, it can be chemically modified and degraded by abiotic processes or more often by microorganisms in the environment. During the following stage organisms will be exposed to the chemical either in its original or in its degraded or transformed form. The uptake of the chemical and degradation products will occur. Organisms may react to such exposure by variety of negligible and sublethal effects or ultimately by death.