There are a number of harmful effects that have been induced by emissions from large vessels carrying bulk liquids. These are reviewed. A number of hazards are cargo-specific. Of special concern are liquids which after discharge or spillage float on the surface of the sea. Sea birds are regularly victims of discharged oil, most of which, however, is discharged from machinery spaces from all kinds of ships. Marine mammals have been contaminated or killed after tankship spills. Water soluble discharges may accumulate in fish and shellfish, thus tainting or contaminating seafood. Spills and discharges of toxic substances create direct hazards to human health. There are also hazards which are not connected with the cargo. Tankships have large hulls which are covered with antifouling paint and consequently emit toxic chemicals. Empty sea-going tankships have to be ballasted with large quantities of water. By discharging the ballast water before loading, foreign material is introduced into that remote marine environment. Connected with this are hazards for the marine environment as well as for human health.