Ecotoxicology: assessing the properties of chemical substances

To predict the behavior of a substance in the environment, in particular its distribution in the various compartments (water, air, soil, sediment), and to assess its possible effects on environmental flora and fauna, it is necessary to study not only its physico-chemical properties, but also its ecotoxicological properties. To understand how a substance moves from water to air, we need to know its volatility (i.e. its Henry's law constant); similarly, to understand how it moves from water to soil, we need to know its adsorption coefficient. It is also essential to know the molecule's degradation and persistence properties, those linked to physico-chemical mechanisms such as hydrolysis and photolysis, as well as the molecule's non-intrinsic properties, such as aerobic or anaerobic biodegradation in soils and water, which are used to determine its fate in the environment. Other criteria, such as bioaccumulation (which can be calculated using Kow), bioconcentration and biomagnification, also help us to understand a molecule's behavior in the environment. Various methods for determining the behavior and fate of substances in the environment, and for assessing their effects on environmental flora and fauna, are described and explained in the following paragraphs.