Attempts to correlate the concentration of organic chemicals in the environment with their production figures have resulted in a large deficit; this includes environmental chemicals such as chlorinated hydrocarbons. It has been assumed that analytical erros accounted for this deficit. Another explanation, however, allows for reactions of compounds under biotic and abiotic conditions. Because of the biostability of many organic chemicals biological transformation mechanisms can bring about slight charge only. By contrast, abiotic environmental factors such as the UV-radiation or decomposition on natural surfaces contribute considerably to the transformation of this substance class. An investigation of such abiotic charges of organic chemicals must therefore pay particular attention to dynamic and catalytic effects primarly attributable to the respective molecular state and interactions with the environment. This paper deals with the photoinduced reactions of organic substances adsorbed on natural surfaces and their significance for the degradability of environmental chemicals.