Compared to other means of transport, and if conducted properly in all respects, shipping has many advantages from an environmental point of view, as well as in terms of safety and transportation economy. This holds true despite the obvious problems of operational discharges of oil and the ever-present risk of large-scale pollution with oil (and chemicals) in the case of a major accident at sea. The advantages of shipping, together with the obvious possibilities for improvements in pollution control, should be kept in mind when assessing the whole spectrum of environmental problems still connected with shipping.

However, like other human activities, shipping is a source of water and air pollution. With some notable exceptions, a list of environmental problems from ships and shipping looks very much like the kind of list one would come up with for municipalities, energy plants, road traffic or industries on land, i.e., land-based sources. To put it simply, ships could be regarded as floating societies with a varying number of inhabitants, from less than ten crew members on a fishing vessel to maybe 3,000—4,000 passengers and crew, sometimes even more, on large ferries and cruising vessels (and large aircraft carriers). Discharges and emissions of non-oily pollution and wastes from shipping include:

  • Emissions of various air pollutants: sulphur dioxide, nitrogen oxides, carbon dioxide, hydrocarbons, carbon monoxide, particles;
  • Operational discharges of chemical wastes: cleaning agents used in machinery spaces, and household chemicals used for washing and cleaning in crew and/or passenger quarters;
  • Accidental discharges of large quantities of chemicals ("chemical spills");
  • Discharge of untreated or insufficiently treated sewage;
  • Discharges of ballast water, including its contents of living organisms (potential future invasive species);
  • Discharges of solid waste/garbage (marine litter);
  • Deliberate dumping of hazardous and industrial waste;
  • Residues from the use of toxic or otherwise environmentally harmful substances for normal maintenance, including antifouling paints, halogenated hydrocarbons in refrigerating equipment and fire-extinguisher, chemicals for treatment of water onboard, etc.

One could also add another environmental problem caused by shipping in coastal areas: Disturbances of wildlife and natural values due to noise, hydrodynamic effects on shores caused by large vessels and high-speed pleasure crafts, and by high-speed boats in wildlife reserves.