Reduction in marine pollution
Between 1992 and 2008, world seaborne trade rose from 17,541 billion tonne miles to an estimated 32,746 billion tonne miles, an increase of around 85%. The carriage of oil and petroleum products accounts for a significant part of this increase, rising by about 40% from 8,043 billion tonne miles to an estimated 11,292 billion tonne miles during the same period.
World seaborne trade (total) tonne miles
Source: Fearnleys Review
In tonnage terms, the amount of oil transported by sea increased from 1,600 million tonnes in 1992 to over 2,400 million tonnes in 2008. Over 34,000 million tonnes was carried over the 16 year period. By contrast, the number of major oil spills during the same period shows a steady reduction. Although serious accidents occasionally occur - the loss of the 'Erika' and 'Prestige' being recent high profile examples - the trend shows a continuing improvement, both in quantity and frequency of oil spills each year.
World seaborne trade (crude oil/oil products) tonnes
Source: Fearnley's Review
The introduction of industry practices such as crude oil washing for oil tankers, coupled with segregated ballast requirements for tankers, has contributed significantly towards reducing operational pollution. The entry into force of the international convention MARPOL 73/78 is credited with a substantial positive impact in decreasing the amount of oil that enters the sea from maritime transportation activities.
Estimated quantity of oil spilt
Source: International Tanker Owners' Pollution Federation
Important advances have been in the design of oily water separating equipment for machinery space bilges and oil tanker discharges, and in the monitoring and control of the discharge of such mixtures. These technological advances have allowed international regulations to be adopted, reducing the permitted operational discharge of oil effluent from machinery space bilges from 100 parts per million (ppm) to 15ppm.
Average number of major oil spills (over 700 tonnes)
Source: International Tanker Owners' Pollution Federation