Transport and handling of hazardous chemicals and chemical products around the world's waters and ports have considerably increased over the last 20 years. Thus, the risk of major pollution accidents has also increased. Past incidents/accidents are, when reported in detail, first hand sources of information on what may happen again. This paper provides an overview of the past tanker accidents in the Baltic Sea and chemical related accidents in seas worldwide. The aim is to find out what can be learned from past accidents, especially from the environmental point of view. The study is carried out as a literature review and as a statistical review. The study revealed that the risk of a chemical accident is highest in seas where the highest tonnes of chemicals are transported, the density of maritime traffic is highest and, of course, in the ship-shore interface where unloading/loading takes place. Incidents involving chemical spills are statistically much less likely to occur than oil spills. However, chemical cargoes can be more dangerous to humans and property because chemicals can be more combustible, poisonous, irritating and reactive. The most important difference between a chemical and an oil spill may be related to response actions. In case of a chemical accident, the air quality or the risk of explosion should be more carefully evaluated before any response actions are taken. In case of chemical spills, the response is more limited in comparison to oil. Actually, very little is known about the actual marine pollution effect of most of highly transported substances. From the environmental point of view, the previous studies have highlighted accidents in which pesticides were released to water, but also substances considered as nonpollutants (vegetable oils) seem to have a negative effect on biota in the water environment.
