The report discusses the input and composition of petroleum oils into the marine environment with special emphasis on factors influencing evaporation rates. Estimations of the atmospheric concentrations distribution of hydrocarbons around an oil spill are given, and a simple model for calculaltion of such distributions is presented. The importance of evaporated oil from surface slicks is correlated to other emissions of organic compounds in a global atmospheric budget for such substances, and the chemical transformation of gaseous hydrocarbons in the atmosphere is discussed. It is conluded that the contribution of hydrocarbon evaporation from oil slicks to the photochemical oxidant pollution is neglectable. The damage caused to humans and the environment on shore is also neglectable in most cases, whereas the human health hazard can be considerable in the close vicinity of the spill.