Oil Pollution

Primary reference(s)

Global Marine Oil Pollution Information Gateway, no date. Sources. Accessed 19 October 2020.

Additional scientific description

Oil discharges to the marine environment may occur from natural seeps, and ocean-based and land-based sources. Examples of ocean-based discharges are oil spills from ships/tankers and offshore platforms and pipelines. Examples of land-based sources are untreated sewage and storm water, rivers, coastal industries, coastal refineries, oil storage facilities, oil terminals and reception facilities. Hydrocarbons can also enter the marine environment as gaseous air pollutants from vapour derived from loading and unloading of oil (UNEP, no date).

Constant sources of a large and ongoing oil input to the marine environment include oil-polluted stormwater and sewage from municipalities, discharges from numerous sources in coastal facilities, gaseous hydrocarbons from cars and motor boats, and many more such on-land or recreational coastal activities that are not always linked to marine oil pollution (Global Marine Oil Pollution Information Gateway, 2005). 

Oil spills can have strong negative environmental and socio-economic impacts (UNEP, no date). Marine and coastal habitats, wildlife species, recreational activities and fisheries, are among the resources and sectors that can be negatively affected by oil spills. Oil harms wildlife in two main ways: through toxic contamination (inhalation or ingestion) or by physical contact, for example:

• Seabirds spend much of their time on or near the sea. This makes them vulnerable to oil spills and they can suffer from hypothermia because the oil destroys the structure of their protective layer of feathers and insulating down; drowning due to their increased weight when oil covers their bodies; poisoning through ingestion or inhalation; and loss of flight, which could affect their reproductive capacity (UNEP, no date).
• Marine mammals, including manatees, dolphins, porpoises, and whales are vulnerable to oil spills owing to their amphibious habits and dependence on air. The consequences of exposure to oil include hypothermia, poisoning from ingestion of oil, congested lungs and damaged airways, and gastrointestinal ulceration and haemorrhaging (UNEP, no date).
• Fish can absorb oil that is dissolved in water though their gills, accumulating it within the liver, stomach, and gall bladder. Although they are able to cleanse themselves of contaminants within weeks of exposure, there may be a period when they are unfit for human consumption (UNEP, no date).
• Sea turtles can be affected when oil enters their eyes and damages airways and/or lungs, from poisoning by absorption through the skin, through the ingestion of contaminated food, and from contamination of the nesting sites, eggs and newly hatched turtles (UNEP, no date).

Oil spills also affect the coastal environment and habitats. Coral reefs and the marine organisms, especially juvenile organisms that live within and around the reefs are at risk from exposure to the toxic substances within oil as well as from smothering. On beaches oil can soak into sand and gravel. Coating on the roots of mangrove trees can kill the trees, and marsh grasses and seagrasses are also affected.

Negative socio-economic impacts include decreased tourism and the closure of recreational, fishing and shellfish areas. Boats and fishing gear may be damaged and human health can be affected through direct contact or inhalation of the oil or by eating contaminated seafood (UNEP, no date).

It may take several years or even decades, before an area or ecosystem has fully recovered from a major oil spill (UNEP, no date).

Metrics and numeric limits

Not applicable.

Examples of drivers, outcomes and risk management

Actions are needed at a number of levels depending on the source of the oil. Globally, international action, such as within the UN International Maritime Organization (IMO), is needed to further control the operational discharges and emissions of oil and waste, as well as air pollutants, from shipping (MARPOL 73/78), and to reduce the risks of major accidents (SOLAS). Measures should build on the regulations set out in these and other conventions with global coverage (UNEP, no date).

Transboundary air pollution (e.g., volatile organic compounds and polyaromatic hydrocarbons from the handling and use of oil products) could be further controlled at the global or regional level via agreements such as the UN Framework Convention on Climate Change, the UN ECE Convention on Long-range Transboundary Air Pollution (Europe and North America), and others (UNEP, date).

The IMO oil pollution manual (IMO, 2005–2019) provides a useful guide for governments of developing countries and for those persons directly associated with the sea transportation and transfer of oil. The manual is divided into six sections: prevention, contingency planning, salvage, combating oil spills, administrative aspects of oil pollution response, and guidelines for sampling and identification of oil spills.

At an individual level, the United Nations Environment Programme recommends a range of actions (UNEP, no date) including: never pour oil into a drain or onto the ground; maintain vehicles to make sure there are no oil leaks; recycle all used oil from, for example, a car; limit paved surfaces since they prevent natural percolation into the ground causing water runoff that ends up at the sea without natural cleaning through filtration; and report oil spills – note date, time and location of the incident.