Follow-up to ecological risk assessment of organotin substances on domestic substances list: chapter 7


7.1 Subcategories that Meet the Criteria Set out in Section 64 of CEPA 1999

Tributyltins are harmful to many aquatic organisms at low concentrations. They are present in the environment as a result of human activity. They have been shown to impose male sexual characteristics on females of some marine gastropods and appear to have the potential to induce sex reversal in some marine fish. Estimated and measured concentrations of tributyltins in some locations in Canada are high enough to cause adverse effects in sensitive organisms. Furthermore, tributyltins meet the criteria for persistence and bioaccumulation set out in the Persistence and Bioaccumulation Regulations, a regulation made under CEPA 1999. Tributyltins are present as a contaminant in commercial tetrabutyltin formulations and probably at much lower levels in dibutyltin formulations.

Tetrabutyltins can be harmful to sensitive aquatic organisms at low concentrations. There is further concern for these substances because they can break down to tributyltins by dealkylation and because commercial formulations of tetrabutyltins contain substantial amounts of tributyltins.

7.2 Subcategories that Do Not Meet the Criteria Set out under Section 64 of CEPA 1999

Monomethyltins, dimethyltins, monobutyltins, dibutyltins, monooctyltins and dioctyltins have the potential to harm aquatic organisms, and commercial formulations of monobutyltin, and dibutyltin may contain tributyltin as a contaminant. However, it is believed that harmful concentrations of these substances would not be reached with industry-wide stewardship practices in place to limit their environmental releases. Releases from other uses of these substances as catalysts or in glass coatings are not expected to be significant, based on the much smaller quantities currently used in these industries.

Triphenyltins can be harmful to sensitive aquatic organisms at low concentrations, and they meet the criteria for persistence and bioaccumulation set out in the Persistence and Bioaccumulation Regulations. They are present in the environment as a result of human activity. It is believed that these substances are no longer in use in Canada.

Tetraphenyltin has the potential to break down to the more hazardous triphenyltins. Commercial formulations of tetraphenyltin likely contain triphenyltin as a contaminant. It is believed that this substance is no longer in use in Canada.

However, given the hazardous properties of fluorotriphenyltin (triphenyltins) and tetraphenyltin, there is concern that new activities for these two substances which have not been identified or assessed, could lead to the substances meeting any of the criteria set out in section 64 of the Act.  It is thus recommended that these two substances be subject to the Significant New Activity provisions specified under subsection 81(3) of the Act, to ensure that any new manufacture, import or use is notified and will undergo ecological and human health risk assessments as specified in section 83 of the Act prior to being introduced into Canada.

 

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