low molecular alcohols, and acids to very refractory compounds that have a biological half-life of several years as for instance DDT and dioxins.
In principle, biodegradation is carried out by many organisms, but in most cases we consider microbiological biodegradation for the most important from an environmental point of view. The biodegradation rates in water and in soil by microorganisms are of particularly interest. It is, however, not a characteristic value that can be used as a constant for a compound, because the biodegradation is strongly dependent on the conditions for the microorganisms in the water and in the soil. The biodegradation is furthermore dependent on the presence or absence of oxygen; it means aerobic or anaerobic conditions. Environmental degradation rates can, however, be found in the literature and in environmental handbooks, but they are always indicated as ranges.