Toxic Ship Paint Additive to Be Banned

Published Sep 7, 2007 12:01 AM by The Maritime Executive

An International Maritime Organization (IMO) treaty banning tributyltin (TBT) from ship paint is expected to be passed soon. An Environmental Protection Agency (EPA) fact sheet on TBT describes the chemical as “extremely toxic to aquatic life and . . . an endocrine-disrupting chemical that causes severe reproductive effects in aquatic organisms.” TBT was a common anti-fouling agent used in ship paint until relatively recently.

Barnacles, algae, and other marine plants and animals encrusting the surface of a ship is known as “fouling” (or “bio-fouling”) and costs more than $10 billion a year. The speed of a vessel encrusted with marine organisms can be reduced by up to 10 percent, while its fuel consumption can increase up to 40 percent, raising its carbon emissions. Barnacles, algae and other organisms can also damage or corrode a ship’s hull.

Many cruise lines and others in the marine industry have already ceased using paint with TBT, but nevertheless, a year after its ratification, the IMO treaty will ban all TBT use on vessels in countries who sign the treaty and on vessels entering those countries’ waters. However, an older ship with TBT on its hull will be allowed if a sealant that makes the toxin inert has been applied to the surface. Any vessel that is discovered violating the treaty will be blacklisted and barred by any other country that has signed the treaty.

Apparently the treaty also outlines procedures for testing and reducing other biocides used on ships’ hulls. Detractors of the treaty claim that it is difficult to create new anti-fouling coatings that do not harm the environment. Currently, paint infused with tin or copper-based compounds is often used on ships to deter fouling instead of a biocide-infused paint. However, these compounds also accumulate in the environment and worries over their ecological effect are increasing.

A possible alternative to biocides, tin, and copper was announced at the EuroNanoForum in Dusseldorf in June of this year: nanotechnology. The new nanotechnology ship coating does not have the same environmental impact because it deters organisms from attaching instead of killing them once they have attached. Tiny cylinders of carbon, carbon nanotubes, are mixed with silicone paint to disturb the paint surface on the molecular level. This impairs a marine organism’s glue molecules, resulting in the organism falling away when the vessel moves. If the IMO TBT treaty is ratified, as many assume it shortly will be, this type of ship coating may soon be in common use.