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1996 Designing Greener Chemicals Award
Rohm and Haas Company
Designing an Environmentally Safe Marine Antifoulant
Innovation and Benefits: Rohm and Haas developed Sea-Nine™, a novel antifoulant to control the growth of plants and animals on the hulls of ships. In 1995, fouling cost the shipping industry approximately $3 billion a year in increased fuel consumption. Sea-Nine™ replaces environmentally persistent and toxic tin-containing antifoulants.
Fouling, the unwanted growth of plants and animals on a ship’s surface, costs the shipping industry approximately $3 billion a year, largely due to increased fuel consumption to overcome hydrodynamic drag. Increased fuel consumption contributes to pollution, global warming, and acid rain.
The main compounds used worldwide to control fouling are the organotin antifoulants, such as tributyltin oxide (TBTO). While effective, they persist in the environment and cause toxic effects, including acute toxicity, bioaccumulation, decreased reproductive viability, and increased shell thickness in shellfish. These harmful effects led to a U.S. EPA special review and to the Organotin Antifoulant Paint Control Act of 1988. This act mandated restrictions on the use of tin in the United States, and charged the U.S. EPA and the U.S. Navy with conducting research on alternatives to organotins.
Rohm and Haas Company searched for an environmentally safe alternative to organotin compounds. Compounds from the 3-isothiazolone class were chosen as likely candidates and over 140 were screened for antifouling activity. The 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (Sea-Nine™ antifoulant) was chosen as the candidate for commercial development.
Extensive environmental testing compared Sea-Nine™ antifoulant to TBTO, the current industry standard. Sea-Nine™ antifoulant degraded extremely rapidly with a half-life of one day in seawater and one hour in sediment. Tin had bioaccumulation factors as high as 10,000-fold, whereas Sea-Nine™ antifoulant’s bioaccumulation was essentially zero. Both TBTO and Sea-Nine™ were acutely toxic to marine organisms, but TBTO had widespread chronic toxicity, whereas Sea-Nine™ antifoulant showed no chronic toxicity. Thus, the maximum allowable environmental concentration (MAEC) for Sea-Nine™ antifoulant was 0.63 parts per billion (ppb) whereas the MAEC for TBTO was 0.002 ppb.
Hundreds of ships have been painted with coatings containing Sea- Nine™ worldwide. Rohm and Haas Company obtained U.S. EPA registration for the use of Sea-Nine™ antifoulant, the first new antifoulant registration in over a decade.
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