The New IMO Treaty to Ban TBT

Wednesday, December 04, 2002
The Diplomatic Conference held (October 1-5, 2001) by the International Maritime Organization (IMO) in London adopted the Draft Convention prepared by The Marine Environmental Protection Committee (MEPC) of IMO for the "Control of Harmful Anti-fouling Systems for Ships." The Convention has been developed to immediately ban the use of Tributyltin (TBT) globally in antifouling paints to "protect the marine environment". The ban on TBT has come about because TBT has detrimental effects on non-target marine organisms. In November 1999, IMO agreed that a Treaty be developed by the MEPC to ensure a ban on the application of TBT based antifouling paints by January 1, 2003, and a total ban on the use of TBT by January 1, 2008. The Convention will prohibit the use of harmful organotins in anti-fouling paints used on ships and establish a mechanism to prevent the potential future use of other harmful substances in anti-fouling systems (

Current Shipyard Practices

Current shipyard practices use freshwater and hydro blasting technologies (high pressure pumps) to washdown (to remove salt, slime, and biofouling) and paint from vessels. This produces washdown wastewater, which is discharged into waterways, contaminating port and harbor bottom sediments. If the TBT Treaty Enters into Force as proposed, the future cost of removal, treatment and disposal of spent antifouling TBT paint residues from ships in shipyards and drydocks and if not ther, then the subsequent cost for removal, treatment and disposal of TBT contaminated dredged material from harbors and waterways could increase significantly: an estimated 12 to 15 times. A key question is: who is liable for these additional costs? In the U.S., only the state of Virginia has discharge regulations (50 part-per-trillion) for TBT in washdown and hydroblast wasters from shipyards and drydocks. When a ship is first placed in a drydock, the vessel is washed down with freshwater to remove salt and prevent corrosion. This washwater is discharged directly to local rivers, estuaries or bays. The hydroblasting can break up the removed paint into paint chips into 10-micron size particles, which can be widely distributed in waterways. Over the past few years, this hydroblasting has become the preferred method to remove antifouling marine coatings (paints) from a ship's hull because of the human health risks from breathing sand blasted materials. Without national regulations on discharge requirements, this practice will continue and significantly increase between 2003-2008 as a result of the Treaty. Contaminated washdown (salt and slime removal) wastewaters from a large ship can exceed 100,000 gallons Hydroblasting (for total paint removal) wastewater from the same ship can exceed an additional 400,000 gallons. Rainfall runoff alone in a drydock can reach 20,000 gallons. Monitoring studies in the U.S. and U.K. have demonstrated that shipyards and dry-docks that remove spent TBT are the current major source of unregulated TBT in the marine environment.

Regulation of Shipyards and Drydocks

At MEPC 46 [a meeting of the IMO Marine Environmental Protection Committee held in London on April 23 through 27, 2001], a group of Delegations [Cyprus, Brazil, Denmark, Liberia, Marshall Islands and Vanuatu (formerly New Hebrides)] stressed the need for language in the treaty requiring safe removal, treatment and disposal of TBT from ships. Subsequently in Plenary, the delegates then instructed the drafting committee to include a new article to regulate the "application or removal of anti-fouling systems" that are banned, requiring that they be "collected, handled, treated and disposed of in a safe and environmentally sound manner to protect the environment and human health". For most of the world, TBT in washdown and shipyard wastewaters can legally be discharged directly into local waters. In some places the discharge from the shipyard is routed through (ineffectively) a municipal waste treatment plant (WWTP).

At MEPC meetings, serious concern was expressed by some experts for the need to identify in the Treaty the necessary regulatory language for: (1) the "safe" removal, treatment, and disposal of "spent" marine antifouling paints (coatings) deemed "harmful" by the Treaty to also "protect the marine environment", and (2) who is liable for the future costs of dredging and disposal of TBT-contaminated port and harbor sediments dredged materials. The requirement for "safe" removal and disposal was subsequently incorporated at MEPC 46 as Article 5 in the Treaty, without it shipyards complying with existing national and local discharge regulations (most have none for the discharge of TBT) could inadvertently release more TBT to ports and harbors in the five-year compliance period than has been leached from ships (hulls) in the past 40 years to the same waters. A future concern of ports and harbors may be the liability for costs associated with the treatment and disposal of dredged sediments that are contaminated with TBT, which has not been addressed.

Treatment of TBT Contaminated Waste

Over the past four years, the U.S. Environment Protection Agency (EPA) — has funded several projects to develop and test wastewater treatment technologies to the Center for Applied Ship Repair and Maintenance (CASRM) and Old Dominion University in Virginia. These studies have found that washdown (salt removal) and hydroblast (paint removal) wastewaters in shipyards can contain up to six million parts per trillion TBT. In Virginia, this wastewater is treated to remove TBT from shipyard discharges. Researchers at Old Dominion University have demonstrated that off-the-shelf waste treatment technologies were not satisfactory for the treatment and removal of TBT in these wastewaters. In addition, U.S., Australian, U.K. and Swiss studies to remove TBT and other metals from wastewaters have found that advanced technologies not commonly utilized in normal sanitary treatment plants are required to remove TBT.

Studies conducted by EPA, U.S. Navy, UK DOE and the Consortium of Organotin Manufacturers Association (ORTEPA) have recorded declining levels of TBT worldwide, yet documented 'hot spots' of TBT in bottom sediments in the proximity of shipyards, drydocks, marina's, ports and harbors.


An example of how contamination can increase the costs for disposal of dredged material is seen in the two alternatives available to the Port of NY/NJ. The Mud Dumpsite, located three miles offshore, has been operational for many decades and has been the traditional disposal area that can accept clean dredged materials. Contaminated "spoils" have to be disposed of at an upland hazardous waste disposal facility. From 1977 to 1991, 90 percent of all NY/NJ dredge spoils were tested and classified, as clean spoils and only one to two percent were contaminated spoils. However, in 1991 the U.S. EPA required bioassay testing. This increased the volume of contaminated spoils.

For contaminated dredged material, the currently available alternative is upland disposal at a hazardous materials storage facility and none are available in the near vicinity. Howland Hook Terminal in Staten Island shipped 150,000 cu. yd. of sediment via barge and rail to Utah at a cost of $17 million or over $110/ cu. yd. Traditional fees for dumping dredge materials at the Mud Dumpsite at this time were in the area of $10/ cu. yd.

Therefore, concern was expressed over the need to identify regulatory language within the Treaty itself for the "safe" removal, treatment and disposal of TBT from ships, and clarification on the issue of liability of future dredging and disposal of TBT-contaminated port and harbor sediments. Under current regulatory practices for most of the world, TBT in washdown wastewaters can be discharged directly into local waters.

It is quite possible that the "regulated" nations can quickly implement new requirements to correct this situation. This implementation will result in the transfer TBT contamination to the "unregulated" countries, which are least able to deal with it. However, at IMO, there is a concern that unregulated countries may unknowingly accept the environmental and human health risks to gain economic benefits from removing TBT from ship's hulls. Market forces are selective for low-cost labor and weak environmental regulation. Unfortunately, most of these developing countries do not have the funding or environmental expertise available for the monitoring, research and technology development essential to treat and dispose TBT washdown wastewaters safely. These activities would defeat the purpose of the Treaty, which is to provide standardized global regulation and ensure that shipowners do not face multiple, fragmented and counter productive national regulations.

It has been estimated that between 70 to 80 percent of the 28,038 ships in global commerce use TBT. Under current practices, the estimated annual increase in wastes in shipyards and drydocks from the Treaty will be: 2.3 million tons of contaminated grit, 18,000 tons of spent paint, 1.8 million paint cans, and 1.1 billion gallons of contaminated washwater (low pressure for salt removal), and if the trend increases of using high pressure hydroblasting to remove spent paint, the volume of wastewater could exceed 5 billion gallons of water needing treatment.

Before the language of the Treaty is ratified, member nations should be aware of the need for regulating the removal and treatment of the spent paint (with biocides) in shipyards by each Member State (Contracting Parties to the Convention) and the permitted discharge limits for treated liquid wastes. In addition, where port and harbor bottom sediments contain TBT's, either from past activities or from paint removal in compliance with the treaty, port authorities would benefit also from defining who is liable for the increased costs for special dredging and treating of the TBT contaminated dredged material.

A Conference was recently held at the Technical University of Denmark in Lyngby, Denmark to bring together researchers on "Environmental Aspects of Handling Heavy Metal and TBT-Polluted Harbor Sediment." International experts indicated that a cost-effective system for remediation of persistent TBT (mostly paint chips) in contaminated bottom sediments might not be available for several years. Without incorporation of Article 5 in the treaty, shipyards complying with national and local discharge regulations could inadvertently release more TBT to ports and harbors in the five-year compliance period than has been released from ships (hulls) in the past 40 years to the same waters. This would be devastating to the marine environment.


When the IMO "TBT Treaty" enters into force, it will be implemented to remove the TBT from ships to protect the marine environment. The regulatory gap between removal and disposal may contaminate more port and harbor bottom sediments. Consequently, both shipyards and drydocks and ports and harbors (who had nothing to do with the Treaty) could be at risk for the liability of treatment and disposal of spent antifouling (TBT) paint residues and subsequent highly (TBT contaminated) bottom sediments in special landfills. The key question then becomes who is liable for the costs of removing and disposing these TBT contaminated spent antifouling paint residues and TBT contaminated dredged materials: shipowners, shipyards, or port and harbor authorities or the paint companies? Costs today for just dredging and disposal in a toxic and hazardous landfill have been estimated to be greater than $150 per cu. yd. … more than 10 times the current costs … and could be significantly greater if contained dredging is required and depending on the availability and location of nearby toxic and hazardous waste landfills and location of sensitive environmental resources in adjacent bays and estuaries. Current waste treatment technology is NOT available for treating TBT contaminated dredged materials, however a few studies are underway to develop them.

Regulation of "Contaminants" in Dredged Materials

Under Annex I of the London Dumping Convention, Contaminants in dredged materials can be ocean dumped if they are not greater than trace background levels, and not be Persistent, Toxic or Bioaccumulate.

Regarding TBT, it is a man made compound that does not occur in the marine environment, it is considered the most toxic material ever added to the marine environment, and filter feeding bivalves readily accumulate TBT. Bioaccumulation Factors (BAF) reported in the literature are as high as 50,000.

As the IMO TBT Treaty is ratified by Member Nations, Port and Harbor Authorities to determine their risks and liabilities from TBT contaminated dredged materials may wish to privately conduct risk assessments to determine the degree and extent of TBT contamination in their waterways and begin to give serious consideration to developing special toxic and hazardous material storage areas which could serve as immediate storage for TBT contaminated dredged materials until suitable technologies can be developed to treat them.

About the Author

Dr. Michael Champ has been involved in pollution and waste management for over 30 years. He has held appointments at the American University, Texas A&M University and the University of Alaska, Fairbanks. He has edited or authored eight books and over 350 publications. He is the co-editor of the major reference work on "Organotins: Environmental Fate and Behavior" 664 pg. (published by Chapman and Hall, Oxford). The book is a summary of over 40 years of research on the use and fate and behavior of the biocide - tributyltin (TBT), which is used as an additive in antifouling paints. He has severed as the resident scholar to the Army Corps of Engineers and to NOAA and a senior science advisor at EPA and a Queens Fellow (QEII) for marine science in Australia. Dr. Champ was asked by the U.S. Congress to help draft the Organotin Antifouling Paint Control Act of 1988, Public Law 100-333. (33 USC 2401). He has chaired four international symposia related to organotins and two for pollution prevention from ships and shipyards. In 2000 and 2001, he was the Technical Advisor to the Marshall Islands, Delegation for IMO MEPC 45, 46, for the New IMO Convention to "Control Harmful Antifouling Systems on Ships". The Treaty was adopted by IMO on October 5, 2001. He is the President of the Advanced Technology Research Project (ATRP) Corporation in Falls Church, Va., ( and has been extensively involved in developing waste treatment technologies and systems for TBT. He was a special consultant to CASRM (Center for Applied Ship Repair and Management) for three years for the development of the Barge Mounted TBT Waste Treatment System.

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