Pollution from land-based activities eventually reach the sea. Sea pollution is generated by land, atmospheric and sea sources. Most of the sea-based pollution is due to oil or ballast water discharged from ships (either intentionally or accidentally due to collision or grounding). Pollution from sea-based sources are mainly oil-based although other waste trash may also come from ships. Other sources include shipping traffic, port operations and off-shore oil and gas exploration and production rigs. Due to the high traffic volume in the Strait, it is difficult to track ship movements, monitor activities and enforce compliance with international rules. As a result ships may take advantage of this to illegally dump wastes during operational activities. This contributes to marine pollution problems in the Strait. The main component in crude oil, polycyclic aromatic hydrocarbons (PAHs), is toxic to marine life and very difficult to clean up. It could remain for years in the sediment and marine environments. Marine species that are constantly exposed to PAHs can exhibit physiological problems and are susceptible to diseases.
In an effort to reduce ship collisions and the resulting discharge of oil, the International Maritime Organisation (IMO) has adopted the Mandatory Ship Reporting System in the Straits of Malacca and Singapore, known as "STRAITREP", as proposed by Indonesia, Malaysia and Singapore. Based on the record of reporting vessels the number of ships passing through the Strait is increasing at approximately 7.5% per year over the last few years (Figure 1.6). About 54% of transiting vessels in the Straits are general cargo vessels and container ships, while about 35% are crude oil and petroleum products carriers. All these vessels are potential sources of pollution. The numbers recorded by the STRAITREP is only that from reporting vessels. This may seriously underestimate the total vessel traffic, as Kamaruzaman (1998) estimated a number of some 600 vessels daily, including fishing vessels, traditional small crafts, pleasure crafts. This gives a number of 213,600 vessels over a period of one year for 1998, which is more than five times the number of reporting vessels recorded in 1999.