Organotin substances (organotins) are tin compounds having 1,2,3 or 4 organic groups attached and are designated as mono-, di-, tri- or tetra-organotin depending on the number of tin-carbon bonds in the molecule.
There are 109 organotin substances on Canada's Domestic Substances List with 104 belonging to nine subcategories: monomethyltins, monobutyltins, monooctyltins, dimethyltins, dibutyltins, dioctyltins, fluorotriphenyltins, tributyltins, tetrabutyltins and tetraphenyltins. They are industrial chemicals.
How are they used?
Some organotins are only used for their pesticidal properties.
Organotins that are not used as pesticides are used primarily as stabilizers for polyvinyl chloride (PVC), a type of plastic.
Other uses for organotins include: additives for PVC food packaging products, depositing tin oxide coatings on reusable glass bottles, and stabilizing lubricating oils, hydrogen peroxide and polyolefins.
Based on the most recent data available, some organotins are currently in use in Canada.
Why did the Government of Canada assess them?
Organotins were identified as a potential concern to the environment based on available information regarding possible persistence, accumulation and potential to cause harm to the environment.
Between August 1994 and March 2000, notifications were received that show significant increases in use quantities and the identification of a potential new route of release to the environment for the nine organotin substance categories.
How are they released into the environment?
There were no reports of current uses of organotins in consumer products. As a result, exposure to organotins is expected to be very low.
Organotins may be released to the environment during product manufacturing and industrial processes. The largest environmental releases of non-pesticidal organotins happens as a result of loss of liquid residues from shipping containers, with smaller releases occurring from storage tanks and transfer lines during processes associated with formulation and manufacturing.
Because organotins have a wide range of uses, they may be released to the environment from many different sources. Some may then stay in the environment for a long time. Two organotin substances, tributyltins and triphenyltins, can accumulate in and cause harm to organisms that live in the water.
Some organotins may enter the environment in a quantity or under conditions that may be harmful to the environment or its biological diversity.
What is the Government of Canada doing?
The Government of Canada has conducted a science-based evaluation of organotins, called a screening assessment.
The Government of Canada has determined that tributyltins and tetrabutyltins (substances which may degrade to tributyltins) are harmful to the environment, because they were found to accumulate and cause harm to organisms. It is recommended that they be added to Schedule 1 of the Canadian Environmental Protection Act, 1999 (CEPA, 1999). Furthermore, tributyltins meet the criteria for virtual elimination (set out in the Government of Canada's Toxic Substances Management Policy).
The Pest Management Regulatory Agency will re-evaluate the remaining uses of tributyltins by 2009-2010 to determine if their use continues to be acceptable under today's standards for health and environmental protection.
The Government of Canada has determined that monomethyltins, monobutyltins, monooctyltins, dimethyltins, dibutyltins, dioctyltins, fluorotriphenyltins and tetraphenyltins are not harmful to the environment, because they were found not to accumulate and cause harm to organisms.
The Government of Canada will consider implementing a Significant New Activity or SNAc provision for fluorotriphenyltin and tetraphenyltins. This would require that any proposed new uses of fluorotriphenyltin and tetraphenyltins would be subject to further assessment before this new activity would be allowed.
