Re-evaluation Note REV2012-03, Re-evaluation Project Plan for Paclobutrazol

Pest Management Regulatory Agency
9 November 2012
ISSN: 1925-0649 (PDF version)
Catalogue number: H113-5/2012-3E-PDF (PDF version)

In Canada, paclobutrazol is under re-evaluation by Health Canada's Pest Management Regulatory Agency (PMRA). The PMRA's pesticide re-evaluation program considers potential risks as well as the value of pesticide products to ensure they continue to meet standards of modern science and current policy established to protect human health and the environment. Under the authority of section 16 of the  Pest Control Products Act, the registrants of paclobutrazol were notified of the initiation of the re-evaluation of paclobutrazol. Following this, the registrants of paclobutrazol technical grade active ingredients in Canada indicated their intention to support all uses included on the labels of commercial products in Canada. This Re-evaluation Note outlines a project plan and timeline for review, as well as summarizes the anticipated area(s) of focus related to the re-evaluation of paclobutrazol.

Paclobutrazol is a plant growth regulator that has been registered in Canada since 1995. Paclobutrazol is currently registered for use on Greenhouse Non-Food Crops (Use-site Category 6). All registered paclobutrazol end-use products are formulated as liquids, to be applied either by drench application or by hand-held spray equipment.

The project plan discussed below outlines the anticipated area(s) of focus and risk assessments required to complete the re-evaluation of paclobutrazol. Should additional information become available during the re-evaluation period that affects the regulatory status of paclobutrazol, the Agency will reconsider the area(s) of focus and risk assessments required. Currently, a proposed re-evaluation decision for paclobutrazol is anticipated to be published for consultation by Winter 2013.

Re-evaluation Project Plan

Human Health Risk Assessment

  • A review of paclobutrazol toxicology was conducted in support of the initial registration and the toxicology database for paclobutrazol is considered complete. Pest Control Products Act hazard considerations will be addressed.
  • Occupational risk assessments previously conducted to support the registered uses will be verified to ensure that they continue to meet the standards of modern science and reflect current policy. Residential exposure will be addressed.
  • Based on the registered use pattern for paclobutrazol, a dietary exposure assessment is not required.

Environmental Risk Assessment

  • Based on the registered use pattern, environmental exposure to paclobutrazol is expected to be limited.
  • Environmental risk mitigation measures will be reviewed to ensure consistency with current label requirements and the Toxic Substances Management Policy (TSMP) will be considered.


  • The value of paclobutrazol will be considered. The viability of alternatives will be examined if risks of concern are identified.

Data Requirements

  • No additional data requirements have been identified for paclobutrazol at this time.

Anticipated Timeline for Re-evaluation

  • A proposed re-evaluation decision for paclobutrazol is anticipated to be published for consultation by Winter 2013.

Additional Information

PMRA documents can be found on our web site at PMRA documents are also available through the Pest Management Information Service. Phone: 1-800-267-6315 within Canada or 1-613-736-3799 outside Canada (long distance charges apply); fax: 613-736-3798; e-mail at

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