Global Trends in Ship-Sourced Marine Pollution 
11 
publications and from information provided by ship owners and their insurers. The statistics clearly show a 
downward trend in the number of large spills (> 700 MT) from tankers, from over 25 per year in the 1970’s to 
around 3 per year in the last 10 years. Despite this positive trend, incidents continue to occur and therefore 
the need remains to be prepared for and able to respond to oil spills. 
Trends in oil spills 
For historic reasons the size of oil spills have been categorized into three categories, small (<7 MT/ <50 bbls), 
medium (7-700 MT/ 50-5,000 bbls) and large (>700 MT/ >5,000 bbls). It is interesting to note that sea 
borne trade continues to increase from 1985, which may imply an increased risk. However, the number of 
spills from tankers over 7 MT shows a steady decline (Fig 1). Interestingly Fig 1 shows that prior to 1985 the 
trends in spills seemingly follow the fluctuations in seaborne traded. The divergence after 1985, is possib 
ly related to increased awareness, the international conventions and the joint industry, government efforts 
through the International Maritime 
Organisation (IMO). The number of large 
incidents (> 700 MT) has dropped 
significantly from an average of 25 per 
year in the 1970’s to just over three 
incidents per year in the past 10 years 
(Fig 2). 
Fig 1: Seaborne oil trade and number of spills 
Fig 2: Number of large (> 700 MT) tanker spills 
since 1970