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Gender-Bending chemicals back in the food chain

“Biocide-free” hull paints “tainted by tin” betray climate change campaign

The respected shipping trade magazine Fairplay reports in its current issue on further research into the presence of organotin biocides in commercial ship hull coatings.

“Dibutyltin (DBT), is 
being increasingly used in foul release coatings (FRC), according to a 
confidential report seen by Fairplay.

Marine coatings manufacturers are using DBT in their products at levels 
that exceed the legally permitted amounts set by the International Maritime Organization” says the Fairplay report.

The use of organotins as a biocide was outlawed by the International Maritime Organisation (IMO), part of the UN, in 2008. Their presence in new hull coating products was first reported by Wikigreen last July. Fairplay now reports on follow-up research and highlights reports that traces of the poisonous chemical are now entering the food chain.

The Fairplay article, headlined “Organotins make toxic return nine years after being outlawed” quotes a confidential research report as saying: “research on organotin content shows levels in 
excess of MEPC limits”, as well as academic research from 2012* and in 2013** that 
“these paints [foul release coatings] appear to be having a toxic effect over and above their claimed mode of action”.

Fairplay points out: “That is a biocidal effect, 
in contravention of the IMO regulation.

The confidential report raises two questions: at what point, given the 2012 and 2013 reports … did the coatings companies become aware that they may be in breach of the regulations, and, second, what have they done to correct the situation?”

There has already been considerable bio-accumulation of organotins over 30 of its use years up till the IMO ban. As the toxic tin compounds settle into sediment they will remain a danger for decades.
An academic quoted in Fairplay says: “Any molluscs or other sediment dwelling benthic organism that is exposed 
to such a contaminant may then bioaccumulate it into its body, passing 
on the contaminant to organisms that consume it, with the potential of biomagnification of the contaminant up the food chain.”

The presence of anti-fouling toxins has already been shown in creatures deep in the Mariana and Kermadec trenches, underlining their persistence and danger to other creatures which feed on them.

A WWF (World Wildlife Fund) statement on the original ban stated: ”For many decades, organotins have been used in anti-fouling paints on ships. Their detrimental effects on the environment were first noticed in oyster farms on the Atlantic coast of France in the late 1970s. Since then, increased levels of organotins have been found world-wide in marine organisms further up the food chain, such as fish, seabirds and marine mammals. These chemicals have been shown to have hormone-disrupting properties in some species,
and humans could also face health risks if they consume contaminated fish.”

The new confidential zreport continues: “FRC silicone-based paints with organotin as a catalyst 
have been shown to be toxic to aquatic species despite this not being 
the claimed intended mode of action. The levels of organotin within the 
paint matrix for some compounds appear to exceed the MEPC limit, thus 
questioning the role of organotin as a catalyst or a toxic inhibitor.”

Betrayal of climate change campaign

In addition to any action the IMO might take concerning violations of its strict ban on organotins, marketing claims that the coatings are “biocide-free” will now come under renewed scrutiny.

The presence of organotins is acknowledged in manufacturers’ Safety Data Sheets for the products concerned, but amounts are claimed to be within IMO limits – a claim that experts say will need to be scrutinized in further testing. But even if the amounts are found to be within limits set by the IMO, any biocidal effect they are found to have would place them in the banned category.

The marketing campaign is now also being seen as a betrayal of the climate change campaign: ship owners have been attracted to the tin-tainted coatings by the offer of cash-exchangeable carbon credits to the tune of 1,500 carbon credits, worth an estimated €12000. A leading environmental campaigner told Wikigreen that the use of dangerous toxins on ships under the guise of reducing energy use was a “cynical pretension”.

• *Feng et al
• ** Carlo Pretti et al

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