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Canada - Final Regulatory Action
Terbufos CAS number:
Date circular:

Chemical name: Phosphorodithioic acid, S-[[(1,1-dimethylethyl)thio]methyl] O,O-diethyl ester

Final regulatory action has been taken for the category: Pesticide

Final regulatory action: The chemical is Severely Restricted

Use or uses prohibited by the final regulatory action:

Formulation Counter 5-G soil Insecticide was phased-out for all the uses as 2004.
Formulation counter 15-G Lock'n Load Soil Insecticide Granular was phased-out for use on corn and rutabaga in 2004

Pesticide use or uses that remain allowed:

Formulation counter 15-G Lock'n Load Soil Insecticide Granular may be used on sugar beets for the short term.

The final regulatory action was based on a risk or hazard evaluation: Yes

Summary of the final regulatory action:

Phase-out of all uses of terbufos except on sugar beets by 2004 as a result of the unacceptable risk to the environment. There are appropriate alternatives for theses uses.
Continued registration for use on sugar beets for the short term due to lack of available alternatives. The area for use of terbufos on this crop is very limited and identified risks to workers from using terbufos on sugar beets can be effectively mitigated by ensuring engineering controls and requirements regarding additional Personal Protective Equipment (PPE) and clothing. Please refer to the PACR 2003-02, Appendix I for proposed engineering controls, PPE and other proposed label statements.

The reasons for the final regulatory action were relevant to: Environment

Summary of known hazards and risks to the environment:

The PMRA currently conducts a deterministic assessment of the environmental risk of pest control products. Environmental risk is characterized using the quotient method, which uses the ratio of the estimated environmental concentrations to the effects end point of concern. Quotient values less than one are considered indicative of a low hazard to non-target organisms, whereas values greater than one are considered to indicate that some degree of hazard exists for effects on non-target organisms.
n-Octanol-water partition coefficients indicate potential for a bioaccumulation of the parent compound and limited bioaccumulation potential for terbufos sulfone or terbufos sulfoxide. Bioaconcentration studies with fish indicate a potential for bioconcentration.
Based on the available toxicity data, risk is classified as high to extremely high for aquatic organisms and in most cases high to extremely high for birds. Similarly, risk to mammals is classified as low for large mammals to high for small mammals. The high risk of terbufos on non-target species has been documented by incident reports of adverse effects.

Expected effect of the final regulatory action in relation to the environment:

Reducing the risk of environmental exposure to terbufos in a manner that is the least disruptive to the need to protect agricultural crops from pests.

Date of entry into force of the final regulatory action: 31/12/2004

No further use was allowed after December 2004 except on sugar beets.