Statistics for oil spills from tankers for close to five decades show a progressive downward trend. The average number of spills greater than, or equal to, 7 tonnes in size has continuously reduced and, since 2010, averages around 7 per year. When we look at large spills, i.e. greater than 700 tonnes, the yearly average, which was around 25 in the 1970s has reduced dramatically to less than 2 since 2010.

Download a graph showing the number of large (>700 tonnes) and medium (7-700 tonnes) spills recorded from 1970 to 2017.

In 2017, two tanker incidents resulting in spills of over 700 tonnes were reported. The first occurred in the Indian Ocean and the second, which ITOPF attended on site, occurred in the Aegean Sea. Four medium sized spills (7-700 tonnes) were also recorded in 2017.

The estimated total amount of oil lost to the environment through tanker incidents in 2017 was approximately 7,000 tonnes, the majority of which can be attributed to the two large incidents mentioned above.

Despite an overall increase in oil trading over the past few decades, it is reassuring to note that oil spills involving tankers have decreased significantly meaning that some 99.99% of oil transported by sea arrives safely at its destination. However, accidents still happen, as demonstrated on 6th January by the tragic incident that occurred off the coast of China involving the oil tanker SANCHI. Learning lessons from incidents such as these will assist tanker owners and governments to continue to work together to reach the highest level of safety and environmental stewardship.

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Background
ITOPF maintains a database of oil spills from tank vessels, including combined carriers, FPSOs and barges. This contains information on accidental spillages of persistent and non-persistent oil since 1970, except those resulting from acts of war. The data held includes the location and cause of the incident, the vessel involved, the type of oil spilt and the spill amount. For historical reasons, spills are generally categorised by size, <7 tonnes, 7-700 tonnes and >700 tonnes (<50 bbls, 50-5,000 bbls, >5,000 bbls), although the actual amount spilt is also recorded. Information is now held on over 10,000 incidents, the vast majority of which fall into the smallest category i.e. <7 tonnes. Information is gathered from published sources, such as the shipping press and other specialist publications, as well as from vessel owners, their insurers and from ITOPF’s own experience at incidents. Unsurprisingly, information from published sources generally relates to large spills, often resulting from collisions, groundings, structural damage, fires or explosions. Number of oil spills in 2017 For 2017, we recorded two large spills (>700 tonnes) and four medium spills (7-700 tonnes).

The first large spill occurred in June when a tanker sank in the Indian Ocean with over 5000 tonnes of oil on board. The second incident involved a tanker which sank off the coast of Greece in September spilling about 700 tonnes of oil.

Of the four medium sized spills two were recorded in January 2017 in South Asia and Southeast Asia; both resulted from collisions and involved the release of bunker fuel. A third spill was reported in East Asia in August. This also involved bunker fuel and resulted from a vessel grounding in bad weather. The fourth medium-sized spill occurred in October in the USA.

Quantity of oil spilt in 2017
The total volume of oil lost to the environment recorded in 2017 was approximately 7,000 tonnes, the majority of which can be attributed to the large spill (>700 tonnes) that occurred in the Indian Ocean in June.

Global oil spill trend
Over the last 48 years, statistics for spills greater than 7 tonnes from tankers show a marked downward trend as illustrated below.

Tanker spills from 1970 to 2017
The number of large spills (>700 tonnes) has decreased significantly over the last few decades and since 2010 averages 1.8 per year.

It is interesting to note that the progressive reduction in the number of large spills is significant when data is analysed per decade rather than annually. Data recorded from 1970 to 2017 illustrate fluctuations in the yearly values within a decade.

A decline can also be observed with medium sized spills (7-700 tonnes). Here, the average number of spills per year in the 1990s was 28.1, reducing to 14.9 in the 2000s and is currently 4.9 for the 2010s (not a complete decade).

While increased tanker movements might imply increased risk, it is encouraging to observe that the downward trend in oil spills continues despite an overall increase in oil trading over the period (figure below right).

Large oil spills
When looking at the frequency and quantities of oil spilt, it should be noted that a few very large spills are responsible for a high percentage of the oil spilt. For example, in more recent decades the following can be seen:

• In the 1990s there were 358 spills of 7 tonnes and over, resulting in 1,134,000 tonnes of oil lost; 73% of this amount was spilt in just 10 incidents.

• In the 2000s there were 181 spills of 7 tonnes and over, resulting in 196,000 tonnes of oil lost; 75% of this amount was spilt in just 10 incidents.

• In the eight year period 2010-2017 there have been 53 spills of 7 tonnes and over, resulting in 47,000 tonnes of oil lost; 80% of this amount was spilt in just 10 incidents.

In terms of the volume of oil spilt the figures for a particular year may be severely distorted by a single large incident. This is clearly illustrated by incidents such as ATLANTIC EMPRESS (1979), 287,000 tonnes spilt; CASTILLO DE BELLVER (1983), 252,000 tonnes spilt and ABT SUMMER (1991), 260,000 tonnes spilt (Figure 7).

Causes of large oil spills
In the period 1970 to 2017, 50% of large spills occurred while the vessels were underway in open water; allisions, collisions and groundings accounted for 59% of the causes of these spills. Perhaps unsurprisingly, these same causes account for an even higher percentage of incidents when the vessel was underway in inland or restricted waters, being linked to some 99% of spills.

Major Oil Spills
A summary of the top 20 major spills that have occurred since the TORREY CANYON in 1967 is given below. It is of note that 19 of the 20 largest spills recorded occurred before the year 2000. A number of these incidents, despite their large size, necessitated little or no response as the oil was spilt some distance offshore and did not impact coastlines. For this reason some of the names listed may be unfamiliar. EXXON VALDEZ and HEBEI SPIRIT are included for comparison although these incidents are further down the list.

Source: Hellenic Shipping News.