19 March 2010
HC Pub.: 100113
ISBN: 978-1-100-15149-6 (print version)
ISBN: 978-1-100-15150-2 (PDF version)
Catalogue number: H113-27/2010-4E (print version)
Catalogue number: H113-27/2010-4E-PDF (PDF version)

Table of Contents

• What Is the Proposed Re-evaluation Decision?
• What Does Health Canada Consider When Making a Re-evaluation Decision?
• What Is Diodofon?
• Health Considerations
• Environmental Considerations
• Measures to Minimize Risk
• What Additional Scientific Information Is Required?
• Next Steps

What Is the Proposed Re-evaluation Decision?

After a re-evaluation of the antimicrobial diodofon, Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the  Pest Control Products Act and  Regulations, is proposing continued registration for the sale and use of products containing diodofon in Canada.

An evaluation of available scientific information found that products containing diodofon do not present unacceptable risks to human health or the environment when used according to the label directions. As a condition of the continued registration of diodofon uses, new risk-reduction measures must be included on the labels of all products. Additional data are being requested as a result of this re-evaluation.

This proposal affects all end-use products containing diodofon registered in Canada. Once the final re-evaluation decision is made, the registrants will be instructed on how to address any new requirements.

Proposed Re-evaluation Decision PRVD2010-04, Diodofon, is a consultation document that summarizes the science evaluation for diodofon and presents the reasons for the proposed re-evaluation decision. It also proposes additional risk-reduction measures to further protect human health and the environment.

The information is presented in two parts. The Overview describes the regulatory process and key points of the evaluation, while the Science Evaluation provides detailed technical information on the assessment of diodofon.

The PMRA will accept written comments on Proposed Re-evaluation Decision PRVD2010-04, Diodofon, up to 45 days from the date of publication. Please forward all comments to Publications.

What Does Health Canada Consider When Making a Re-evaluation Decision?

The PMRA's pesticide re-evaluation program considers potential risks, as well as value, of pesticide products to ensure they meet modern standards established to protect human health and the environment. Regulatory Directive DIR2001-03, PMRA Re-evaluation Program, presents the details of the re-evaluation activities and program structure.

Diodofon, one of the active ingredients in the current re-evaluation cycle, has been re-evaluated under Re-evaluation Program 1. This program relies as much as possible on foreign reviews, typically United States Environmental Protection Agency (USEPA) Reregistration Eligibility Decision (RED) documents. For products to be re-evaluated under Program 1, the foreign review must meet the following conditions:

• it covers the main science areas, such as human health and the environment, that are necessary for Canadian re-evaluation decisions;
• it addresses the active ingredient and the main formulation types registered in Canada; and
• it is relevant to registered Canadian uses.

Given the outcome of foreign reviews and a review of the chemistry of Canadian products, the PMRA will propose a re-evaluation decision and appropriate risk-reduction measures for Canadian uses of an active ingredient. In this decision, the PMRA takes into account the Canadian use pattern and issues (for example, the federal Toxic Substances Management Policy).

Based on the health and environmental risk assessments published in a 2008 RED, the USEPA concluded that diodofon was eligible for reregistration provided risk-reduction measures were adopted. The PMRA compared the American and Canadian use patterns and found the USEPA assessments described in this RED were an adequate basis for the proposed Canadian re-evaluation decision.

For more details on the information presented in this overview, please refer to the Science Evaluation section of Proposed Re-evaluation Decision PRVD2010-04, Diodofon.

What Is Diodofon?

Diodofon is an antimicrobial used as a material preservative in latex paints, pigment dispersions, coatings, latex caulks and adhesives, leather tanning and paper production (wet lap and sheet pulp). Diodofon is handled by professional workers and is added during the manufacturing process of treated articles and materials using open pour or closed systems. Homeowners can use household products which already contain this active ingredient.

Health Considerations

Can Approved Uses of Diodofon Affect Human Health?

Diodofon is unlikely to affect your health when used according to the revised label directions.

People could be exposed to diodofon while working with treated materials during their manufacture or through residential exposure (in other words, homeowners may be exposed during application of the treated product, or postapplication to the treated materials, for example paint). The PMRA considers two key factors when assessing health risks:

• the levels at which no health effects occur; and
• the levels to which people may be exposed.

The dose levels used to assess risks are established to protect the most sensitive human population (for example, children and nursing mothers). Only uses for which exposure is well below levels that cause no effects in animal testing are considered acceptable for continued registration.

The USEPA concluded that diodofon was unlikely to affect human health provided that risk-reduction measures were implemented. These conclusions apply to the Canadian situation, and equivalent risk-reduction measures are required.

Environmental Considerations

What Happens When Diodofon Is Introduced Into the Environment?

Diodofon is unlikely to affect non-target organisms when used according to the revised label directions.

The USEPA concluded that indoor uses of diodofon were unlikely to affect non-target organisms provided that additional advisory statements to further protect the environment were implemented. These conclusions apply to the Canadian situation.

Measures to Minimize Risk

Labels of registered pesticide products include specific instructions for use. Directions include risk-reduction measures to protect human and environmental health. These directions must be followed by law. As a result of the re-evaluation of diodofon, the PMRA is proposing further risk-reduction measures for product labels.

Human Health

• Additional protective equipment for handlers
• Removal of uses from wettable powder and dust/powder labels
• Additional advisory label statements indicating that end-use products intended for leather preservation are limited to leather tanning drums only
• Rate reduction for products used in the preservation of exterior latex paints
• Additional advisory label statements prohibiting use in toys or finger paint
• Additional advisory label statements indicating use is for carpet backing only

Environment

• Additional advisory label statements to reduce potential surface and groundwater contamination

What Additional Scientific Information Is Required?

Data are required as a condition of continued registration under section 12 of the Pest Control Products Act. The registrants of this active ingredient must provide these data or an acceptable scientific rationale to the PMRA within the timeline specified in the decision letter. Appendix I of Proposed Re-evaluation Decision PRVD2010-04, Diodofon, lists all data requirements.

Next Steps

Before making a final re-evaluation decision on diodofon, the PMRA will consider all comments received from the public in response to Proposed Re-evaluation Decision PRVD2010-04, Diodofon. The PMRA will then publish a Re-evaluation Decision that will include the decision, the reasons for it, a summary of comments received on the proposed decision and the PMRA's response to these comments.