Oil spills from tankers fell by 99.8 percent between 1979 and 2020
In 1979, tanker accidents dumped about 636,000 tonnes of oil into the sea across 92 incidents. By 2020 the figure had shrunk to around 1,000 tonnes from just three, an all-time low. Stricter international rules on how tankers are built and run are behind the change.
A tanker is a ship built to carry or store liquids or gases in bulk. The main kinds are oil tankers, chemical tankers and gas carriers, but tankers also haul vegetable oil, citrus juice, molasses and wine. Sizes run from a few hundred tons for serving small harbours to several hundred thousand tons for long voyages, and inland versions work rivers and canals. The United States Navy calls its refuelling tankers oilers.
Before the late 19th century, bulk liquid transport was simply impractical. Liquids travelled in casks, which is where the word tonnage comes from: it measured how many tuns of wine a hold could take. Wooden hulls leaked, so iron and steel were needed to keep cargo from spoiling. Liquids have to be pumped, so steam-powered pumps and shore terminals had to be developed. A large body of liquid sloshing across the full width of a hull can capsize a ship, a danger known as the free surface effect, which designers solved by dividing tanks into many compartments.
The oil industry adopted tankers first, moving refined fuel from refineries to shore storage for onward delivery. Other trades followed once bulk shipping proved cheaper, and even the Guinness brewery sent its stout across the Irish Sea by tanker. Specialised types now handle dangerous chemicals, oil products and liquefied natural gas, some carrying several cargoes at once. Supertankers carry Middle Eastern oil around Africa; the Seawise Giant, scrapped in 2010, measured 458 metres long and 69 metres wide. As of 2005, just over 4,000 tankers of at least 10,000 long tons deadweight were in service.
Wrecks such as the Torrey Canyon, Amoco Cadiz and Exxon Valdez shaped modern regulation. International Maritime Organization rules under the MARPOL and SOLAS conventions govern pollution and construction, including systems that fill cargo tanks with inert gas so an explosive atmosphere cannot form.
Source: Tanker (ship)
