This external costs category includes a vast set of sea pollution phenomenon, due to land or marine activities. As to the United Nation Global Action Programme for the protection of marine environment, seas may be polluted mainly by the release of hydrocarbons (traces releases by land sources, oil spills, etc.), of pathogen agents (f.e. contained in sewage waters), of chemical toxic substances or nutrients from agricultural activities (biocides, fertilizers, etc.), of heavy metals, of radioactive substances in traces and – not last for relevance- of those solid wastes that can be easily seen on many European beaches.
Talking about oil pollution, this is often attributed to tanker oil spills and to smaller accidents in bunkering operations; indeed there are many other smaller but more diffused oil release sources. When exhausted lubricants are not correctly recovered, they are usually discharged into sewages or inland water bodies and they may finally end up in the coastal marine waters. Another important oil pollution source is given by vehicle lubricants drippings on roads, washed up by rains and finally polluting soils, waters or sewage networks. Hydrocarbons releases in the sea may also come from industrial non controlled activities, from cargo and lubricating operations carried out in harbours and inland terminals, from offshore oil extraction platforms, from illegal shipping operations as discharges of bilge oils or sludges. It must be reminded that a significant quota of marine oil pollution has natural origins: this happens with oil infiltrations from the oceans and with erosion of sedimentary rocks. From the external costs point of view, unintentional or operational oil spills may produce large effects, the final extent of which depend from the uniqueness of the impaired natural resources (restoration costs, if restoration measures are technically possible), from the intensity of the impaired economic activities or assets (fishing, marine tourism, damaged infrastructures, etc.) and –at the origin of the oil spill impact pathways- from “primary impact factors” such as the chemical and physical nature of the oil spill, distance of spill from the coast, weather and sea conditions, water temperature and marine currents, the timeliness and intensity of the first emergency measures in order to control the “black tide”. In the most of tanker spills, the evolution of the polluting event takes a period of time that can be long enough for emergency forces to intervene and control the event, preventing the formation of harmful impact pathways. The “port of refuge” emergency planning principle has a rationale in an impact pathways controlling approach. .
For the economic point of view the main effects of oil pollution may be summarised as follow:
Effects on the local economy:
- Infrastructure damage (harbours, berths, etc.) and impairment of related services;
- Contamination of swimming, snorkeling and tourism areas
- Effects on fishing and watercolture
- Reduction of tourism and related commercial activities
Effects on fauna:
- Mammals and birds population impairment
- Fishes population reduction
- Mussels and sediment living organism contamination
- Toxic chemicals tissue absorbtion and transmission into the food chain
Effects on flora:
- Damages to algae and lichens population
- Damages to coral reefs
- (in case of fire) Acute health effects associated to NOx, SO2, VOCs, aromatic hydrocarbons, PCB and other pollutants emissions
- Damages to agriculture and toxic cloud rains
Because of its complexity and specificity, the damage to marine environment constitutes one of the research borders of the external costs valuation.