We risk environmental catastrophes by ignoring what we put into the oceans. 

WikiGreen aims to shine light into the depths of this ignorance.

We welcome your contributions. If you prefer to remain anonymous, your confidentiality is protected by Icelandic law.

Our panel

Our editorial panel includes shipping and coatings industry professionals, academic researchers specialising in the marine environment, and journalists.

We verify information independently before publication.

Cruise ships risk poisoning arctic waters with sex-change biocides

Ships from leading cruise lines including Carnival, Cunard, P&O, Celebrity, Crystal, Le Ponant and Princess may be placing marine life in the fragile arctic regions at risk by using hull coatings containing tin, banned as a biocide by the International Maritime Organisation in 2008.

The coatings are sold as ‘biocide-free’, but recent revelations that they contain tin have prompted at least one major cruise line to consider abandoning them.

Environmentalists are now particularly concerned about the effects of tin entering the relatively pristine and fragile ecosystems which are the favored destinations of cruise lines. This adds to other concerns accompanying the frequent presence of large cruise ships in areas such as Venice, the Caribbean, the Antarctic and the Arctic.


The cruise industry is a major user of the ‘foul-release’ coatings, so called because their silicone base is supposed to shed fouling without the use of biocides, and to decrease fuel consumption. They are sold at several times the cost of regular hull coatings. The Crystal Serenity, which recently became the first luxury cruise liner to complete a voyage through the Arctic North-West passage, uses one of the affected products, Intersleek 1100SR, as detailed on the ships twitter stream: “Congratulations to hashtag/crystalserenity? for completing her Northwest Passage voyage. She is coated with Intersleek1100SR.

The discovery that the coatings contain tin may come as an embarrassing problem for owners of affected ships, who are already under fire on several environmental fronts. Tin-based antifouling was widely used until the 2008 ban but its effects have been described as ‘the worst catastrophe to hit the world’s oceans’, after research revealed it was causing sex change and chemical castration in key marine species. Due to its long active life in sediments, tin used on ships before the ban continues to be a serious problem around busy shipping lanes, ports and estuaries in and around tourist destinations.


Lab analysis

Lab tests on a sample of Intersleek 1100SR , the leading ‘foul-release’ coating, were first published on Wikigreen earlier this year. The tests revealed the presence of the organotin compound dibutyltin (DBT), strictly banned as an antifouling agent since 2008. Its presence was later confirmed by the manufacturers, International Paint.

Manufacturers of the ‘foul-release’ coatings have claimed that the tin in their coatings is explained by its use as a catalyst, left over from the production process and falling within legal limits. They have also suggested that since the tin is not added “for biocidal or antifouling purposes”, it does not violate the precise wording of the ban. Environmentalists and marine biologists remain very concerned the presence of any quantity of tin in the coatings, after what has generally been assumed to be a complete and total international ban.

Toxic amounts doubled

In a further development, additional documents handed to Wikigreen suggest that the amount of tin present in current coatings is more than double the highest level required for its use as a catalyst.

The earlier Wikigreen story reported that a sample of Intersleek 1100SR had been analysed at a respected European lab, showing 1273 mg of tin per kg of wet paint. The tin content of the dried coating was estimated to amount to a third of a kilogram of tin in a 20-litre can of paint, representing as much as 132 kg of tin on an average size vessel. International Paint responded that the quantity of tin contained in the coating is 1,000 mg per kg., below the maximum 2,500 mg per kg limit allowable under the International Maritime Organisation’s Anti Fouling Convention.

An industry insider however has discovered the results of research conducted in 2005, in a paper entitled “Bioassays and selected chemical analysis of biocide-free antifouling coatings”. The research examined foul-release coatings being produced at that time. The amount of tin remaining in the 2005 products ranged from undetectable amounts to 628 mg/kg – less than half the current levels. The increased levels have led to suspicions that the tin is being used as a covert antifoulant, since catalysts without tin are readily available.


Replacement urged

The 2005 research also found that “Some biocide-free paints contained leachable, toxic and dangerous compounds in the dry film, some of which may act as substitutes for biocides or are incorporated as plasticizers or catalysts.”

The authors concluded that “Due to concern about the use of organotin compounds some raw material suppliers and paint manufacturers have switched to other curing systems” and suggested that “Attempts should be made to replace organotin catalysts in silicones which are exposed for years to sea water to avoid any contamination”


Cruise controls

Wikigreen asked several of the cruise lines to comment on whether they were aware that the coatings in use on their ships contain tin. A representative of the Carnival Corporation (representing several lines, including Princess Cruises) replied only that: “Protecting the ocean environment is a top priority at Princess Cruises and all of the Carnival Corporation brands. Our hull coatings are fully compliant with IMO standards and have been certified by independent classification societies”. Cunard, P&O, Celebrity, Crystal and Le Ponant have all thus far failed to respond.

Although cruise vessels are not the only sector of shipping to have adopted these coatings they are major users and a growing sector. The world fleet of cruise ships now stands at over 230, but with cruise industry growth of about 8 per cent per year it is expected to double before 2020.

Calls are already being made for Arctic nations to consider limiting the size of vessels and banning the use of heavy fuel oil in the region. The concerns have been amplified by the Crystal Serenity’s voyage through the North-West passage – the ship carries up to 1,700 passengers and crew, with tickets at a minimum price of $19,755.


One Response to Cruise ships risk poisoning arctic waters with sex-change biocides

  • Crystal Serenity was escorted through the North-West passage by Ernest Shackleton, where the underwater hull has for years been protected with a non-hazardous hard STC coating. This coating has been proved to be completely toxic-free even when brushed.

Leave a Reply

Your email address will not be published. Required fields are marked *