20 April 2017

Industry Lobby Calls for IMO to Investigate Antifouling Coating Accusations  

High Levels of Banned Chemicals May Still Be Present in Some Products

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Shipping News Feature WORLDWIDE – In the past few years worries over chemical biocidal antifouling coatings have largely subsided with the advent of robot hull cleaning systems and the tightening of regulations regarding toxicity. Now however a note of concern has been raised, admittedly by some with a vested interest, calling for the International Maritime Organization (IMO) to investigate the levels of tin in silicone-based foul release systems and other ships hull coatings.

Subsea Industries, the manufacturer of the Ecospeed hull coating system, claims that, whilst use of the organotin tributyltin (TBT) was outlawed as an active biocide almost ten years ago, the IMO has ‘left the door open’ to abuse by allowing tin to be used as a catalyst which, it says, masks the fact that, in some cases, the amount of organotin present suggests it could in fact be the active toxic agent.

While shipowners may have thought the use of organotins in marine hull coatings was completely outlawed in 2008 with the ban on tributyltin (TBT), they can still be used as a catalyst if organotin content does not exceed the allowable limit of 250mg/1kg of paint. Dibutyltin and dioctyltin are the organotins under most scrutiny and Subsea’s comments are supported by Dr Rik Bruer, a former researcher at Netherlands research institute TNO and now managing director of Finsulate, a manufacturer of a non-toxic antifouling wrap, who commented:

"I have seen for myself that something strange happened with the formulation of these foul release coatings. Until 2002 I worked at TNO and at that time the chemistry of the silicone foul release coatings seemed to be in order. There was some organotin in there, but this is known to be a catalyst for curing these coatings.

“About a year ago, I studied the Materials Safety Data Sheets of recent versions of these foul release coatings and it turns out that the amount of ‘catalyst’ added is more than ten times higher compared to 2005. For me there is no debate that there is a purpose beside the catalyst activity and that the risk of spreading tin compounds again to kill marine life is eminent.”

Dr Bruer, and others supporting his views, pose the question as to why organotins are still being used as catalysts in this way when even small amounts leaching into the surrounding water can have serious deleterious effects on flora and fauna just as TBT does. Professor Daniel Rittschof, a specialist in barnacles and other arthropods at the Duke University in North Carolina said:

“Part of the problem is that at very low concentrations, less than 1/1000th of the amount in coatings, organotins cause molluscs to change sex and/or become behaviourally castrated, with male following male pheromones and female following female pheromones. The effects of dibutyltin and probably dioctyltin are similar to TBT. Organotins at very low levels alter enzymes that process steroids, which is why molluscs change sex.”

Subsea Industries chairman, Boud Van Rompay, whilst admitting that he can hardly be considered unbiased whilst his company is a manufacturer of non-toxic hull coatings, raises a legitimate point in asking whether silicone-based hull coatings are relying on the presence of organotins as an active ingredient to prevent fouling, rather than a catalyst to deliver ‘non-stick’ properties to the coating. He observes:

“Only a proper and independent investigation will determine whether some paints exceed the permitted levels. But like most people in the industry, we had thought the days of toxic tin in hull coatings was long gone. It is very worrying to hear this may not be so. Independent research on the tin content of some foul release coatings appears to have identified levels allegedly exceeding the limits set by the IMO’s Marine Environmental Protection Committee (MEPC). This tends to support earlier research indicating that this type of paint appeared to be having a toxic effect on aquatic fauna in a way that led to the ban on tributyltin (TBT) in 2008.

“However, it is important that independent laboratories assess the biofouling on these hulls, underwater or in drydock, to measure the levels of toxicity. We need to have clear evidence on how these silicone-based coatings are affecting marine organisms, which are vital to the marine eco system.”

Citing a 2013 study that noted dibutyltin ‘showed toxicity toward fish and shrimp’ even when used as a catalyst, Van Rompay’ concluded: “There are studies available in the public domain that should have already raised alarm bells.”

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