The
compounds slowly "leach” into the sea water, killing barnacles and other marine
life that have attached to the ship - but studies have shown that these
compounds persist in the water, killing sealife, harming the environment and
possibly entering the food chain. One of the most effective antifouling paints,
developed in the 1960s, contains the organotin tributyltin (TBT), which has been
proven to cause deformations in oysters and sex changes
(i.e.,
imposex) in whelks.
In 5 October 2001, at the end of a five-day Diplomatic Conference held at IMO Headquarters in London, the Organization adopted the International Convention on the Control of Harmful Anti-fouling Systems on Ships (AFS Convention).
The AFS Convention came about in response to Assembly resolution A.895 (21) Anti-fouling systems used on ships, adopted by IMO in November 1999, which called on IMO’s Marine Environment Protection Committee (MEPC) to develop an instrument, legally binding throughout the world, to address the harmful effects of anti-fouling systems used on ships.
The resolution calls for a global prohibition on the application of organotin compounds which act as biocides in anti-fouling systems on ships, which started in 1 January 2003, and a complete prohibition by 1 January 2008.
The harmful environmental effects of organotin compounds were recognized by IMO in 1990, when the MEPC adopted a resolution which recommended that Governments adopt measures to eliminate the use of antifouling paint containing TBT on non-aluminium hulled vessels of less than 25 metres in length and eliminate the use of antifouling paints with a leaching rate of more than 4 microgrammes of TBT per day. Some countries, such as Japan, have already banned TBT in antifouling paint for most ships.
Alternatives to TBT paint include copper-based coatings and silicon-based paints, which make the surface of the ship slippery so that marine organisms will be easily dislodged d off as the ship moves through water. Further development of alternative anti-fouling systems is being carried out. Underwater cleaning systems avoid the ship having to be put into dry dock for ridding the hull of sealife, while ultrasonic or electrolytic devices may also work to rid the ship of foulants.
For current Information, please refer to the IMO website.
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