Consultation document: proposed risk management for non-pesticidal uses of tributyltin: chapter 3
Pesticidal uses of tributyltins are regulated by PMRA under the authority of the PCPA. In the past, tributyltin compounds had entered the environment mostly from their pesticidal uses. However, action has already been taken on tributyltin pesticides with the greatest exposure to the environment. The use of tributyltins in antifouling paints on ship hulls has been prohibited in Canada since January 1, 2003, following the PMRA's special review.
The remaining pesticides registered under the PCPA for use in wood and material preservatives have more limited environmental exposure. In a regulatory consultation document published July 15, 2010, Health Canada proposed a phase-out of all remaining pesticidal uses of tributyltin compounds. A final regulatory decision is pending consideration of comments received during the consultation process.
Non-pesticidal tributyltin compounds may enter the environment because of their incidental presence in other butyltin products (mono- and dibutyltins, and tetrabutyltin) and from the environmental breakdown of tetrabutyltin.
An Environmental Performance Agreement Respecting the Use of Tin Stabilizers in the Vinyl Industry has been in place since March 10, 2008, to prevent the release of tin stabilizers (mono- and dibutyltins) into the environment, and therefore the release of the incidental presence of tributyltins (EC, 2008). The EPA was developed by Environment Canada, the Tin Stabilizers Association (TSA), and the Vinyl Council of Canada (VCC). All the vinyl compounding facilities using tin stabilizers in Canada must implement all of the practices set out in the Guideline for the Environmental Management of Tin Stabilizers in Canada (VCC, TSA, 2006). This Guideline was developed by the VCC and the TSA and is applicable to companies that manufacture or use tin stabilizers for PVC processing. It is estimated that implementation of the practices in the Guideline has substantially reduced the potential for release to the environment of organotins, and consequently any tributyltins incidentally present.
In addition, to manage releases of tetrabutyltin to the aquatic environment, a Code of Practice is being developed. It is noted that the level of tributyltins found in tetrabutyltin is reduced to less than 1% during the production of mono- and dibutyltin compounds. Therefore, any incidentally present tributyltins that may be released with tetrabutyltin, as well as any potential breakdown of tetrabutyltin into tributyltins, will be controlled by the proposed Code.
The Code will identify best management procedures and practices for activities involving the import, distribution, manufacture and use of tetrabutyltin in Canada. Environment Canada is currently consulting on this proposed Code of Practice, and to that effect, a separate working document is also available to stakeholders.
There is also a Ministerial Condition No 13618 in place for tetrabutyltin under paragraph 84(1)(a) of CEPA 1999. The Ministerial Condition imposes conditions restricting its use, and prescribing handling and disposal procedures to control its release to the environment. As the Code of Practice will incorporate the requirements of the Ministerial Condition already in place, the Ministerial Condition would no longer be necessary and therefore Environment Canada will consider rescinding this Condition once the Code of Practice is in place.
The European Union has adopted a decision on May 28, 2009, that would prohibit the use of triorganotin compounds and of dibutyltins in articles where the concentration in the article, or part thereof, is greater than the equivalent of 0.1% by weight of tin (EU, 2009). The prohibition for triorganotins has been in effect as of July 1, 2010, and the one for dibutyltins will be in effect on January 1, 2012.
The International Maritime Organization's International Convention on the Control of Harmful Anti-fouling Systems on Ships was adopted in October 2001 and came into force in September 2008. The Convention stipulates that effective January 1, 2003, ships shall not apply or re-apply organotin compounds (including tributyltins) that act as biocides in antifouling systems. The Convention also stipulates that effective January 1, 2008, ships shall either not bear such compounds on their hulls or external parts or surfaces, or shall bear a coating that forms a barrier to such compounds leaching from underlying non-compliant antifouling systems (IMO, 2001). Canada is a Party to this Convention.
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