23 July 2010
HC Pub: 100321
ISBN: 978-1-100-16169-3 (print version)
ISBN: 978-1-100-16170-9 (PDF version)
Catalogue number: H113-9/2010-18E (print version)
Catalogue number: H113-9/2010-18E-PDF (PDF version)

Summary

Table of Contents

• Proposed Registration Decision for Thymol
• What Does Health Canada Consider When Making a Registration Decision?
• What Is Thymol?
• Health Considerations
• Environmental Considerations
• Value Considerations
• Measures to Minimize Risk
• Next Steps
• Other Information

Proposed Registration Decision for Thymol

Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the  Pest Control Products Act and  Regulations, is proposing full registration for the sale and use of Thymol E_9509758and Thymovar, containing the technical grade active ingredient thymol, to control Varroa mites (Varroa destructor) on honey bees (Apis mellifera).

An evaluation of available scientific information found that, under the approved conditions of use, the product has value and does not present an unacceptable risk to human health or the environment.

This summary describes the key points of the evaluation, while the Science Evaluation section of Proposed Registration Decision PRD2010-18, Thymol provides detailed technical information on the human health, environmental and value assessments of thymol and Thymovar.

What Does Health Canada Consider When Making a Registration Decision?

The key objective of the Pest Control Products Act is to prevent unacceptable risks to people and the environment from the use of pest control products. Health or environmental risk is considered acceptable if there is reasonable certainty that no harm to human health, future generations or the environment will result from use or exposure to the product under its proposed conditions of registration. The Act also requires that products have value when used according to the label directions. Conditions of registration may include special precautionary measures on the product label to further reduce risk.

To reach its decisions, the PMRA applies modern, rigorous risk-assessment methods and policies. These methods consider the unique characteristics of sensitive subpopulations in humans (for example, children) as well as organisms in the environment (for example, those most sensitive to environmental contaminants). These methods and policies also consider the nature of the effects observed and the uncertainties when predicting the impact of pesticides. For more information, please refer to the following:

• Protecting Your Health and the Environment
• Pesticide Registration Process
• Pesticide Risk Reduction Program

Before making a final registration decision on thymol, the PMRA will consider all comments received from the public in response to this consultation document. The PMRA will then publish a Registration Decision on thymol, which will include the decision, the reasons for it, a summary of comments received on the proposed final registration decision and the PMRA's response to these comments.

For more details on the information presented in this summary, please refer to the Science Evaluation section of Proposed Registration Decision PRD2010-18, Thymol.

What Is Thymol?

Thymol is a volatile oil which is found in oil of thyme. While the mode of action of thymol is not known, it is believed that the site of action is the nervous system in insects. Thymol vapourizes at varying rates, depending on temperature. Thymovar is a product containing thymol for control of varroa mite (Varroa destructor) in honeybee hives. Through volatilization from the Thymovar wafers, thymol vapours build up in the hive. Varroa mites are more sensitive to thymol than bees; therefore, the thymol vapours are at a high enough concentration to be toxic to varroa mites but are not high enough to harm bees. Thymol is not effective on mites within brood cells; therefore, the treatment period must be long enough to ensure that the brood in cells which are capped at the onset of treatment have time to emerge.

Health Considerations

Can Approved Uses of Thymol Affect Human Health?

Thymol is unlikely to affect your health when used according to label directions.

Exposure to thymol may occur when handling and applying the end-use product, Thymovar. When assessing health risks, two key factors are considered:

• the levels where 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 the exposure is well below levels that cause no effects in animal testing are considered acceptable for registration.

The technical grade active ingredient, Thymol E_9509758, is of moderate acute toxicity by the oral route, slight acute toxicity by the dermal route, and low acute toxicity by inhalation. Thymol is corrosive to the eyes and extremely irritating to the skin. Additionally, it is a known respiratory irritant and a dermal sensitizer. Based on available information and a long history of safe use as a food additive, cosmetics ingredient, and its presence in foods and beverages, exposure to thymol is unlikely to result in any short-term toxicity, prenatal developmental toxicity or genotoxicity.

Residues in Water and Food

Dietary risks from food and water are not of concern.

The amount of thymol present as residue in honey following the application of Thymovar in beehives is not expected to exceed natural or artificial amounts typically used to flavour foods and beverages. Therefore, the direct application to beehives with wafers impregnated with thymol is not expected to result in any dietary risk due to exposure from food or water.

Occupational Risks From Handling Thymovar

Occupational risks are not of concern, when Thymovar is used according to label directions, which include protective measures.

Pesticide applicators can come into direct contact with thymol when handling and applying Thymovar to beehives. Potential exposure routes include direct contact with the skin and indirect contact of thymol vapour with the eyes and lungs. Although thymol is known for its corrosive and irritating properties, the product label contains a number of mitigative measures to limit potential exposure to the applicators.

As Thymovar is a Commercial class product that requires direct application inside beehives, bystander exposure is expected to be negligible and therefore not of concern.

Environmental Considerations

What Happens When Thymol Is Introduced Into the Environment?

Thymol is a naturally occurring essential oil that transforms rapidly under environmental conditions. During the use of Thymovar for control of varroa mite in beehives, exposure of the chemical to the environment is expected to be limited. The product is applied as textile wafers containing the active ingredient thymol, which evaporates into the closed beehives. Environmental exposure would occur primarily through leakage during application or from improper disposal of used wafers. Based on limited environmental exposure, the chemical's natural occurrence and the likelihood for relatively rapid transformation under environmental conditions, the proposed use of thymol is not expected to pose a significant risk to the environment. Therefore, further review of the environmental chemistry, fate, and toxicology of thymol was not considered necessary.

Value Considerations

What Is the Value of Thymovar?

Thymovar controls varroa mite (Varroa destructor) in honeybee hives.

Efficacy studies from various locations, including Quebec, Switzerland, Portugal, Turkey, Italy, Germany, Greece, and the Netherlands, were reviewed in support of Thymovar. These studies found that Thymovar generally provided control of varroa mites in excess of 90% when applied according to label directions, with no significant adverse effects. Thymovar is used for control of varroa mite in honeybee hives by applying 2 consecutive applications of ½ a wafer in nucleus hives, 1 wafer in 1 storey hives, or 2 wafers in 2 storey hives. Applications are left in the hive for 3-4 weeks. Applications must only be made when temperatures are above 12°C and below 30°C. No significant adverse effects are expected provided that the Thymovar wafers are not placed directly over brood and temperatures do not exceed 30°C.

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.

The key risk-reduction measures being proposed on the label of Thymovar to address the potential risks identified in this assessment are as follows.

Human Health

The statements, "WARNING - POISON", "DANGER - CORROSIVE TO EYES", and "DANGER - SKIN IRRITANT" have been included on the principal display panel of the general label and AHarmful or Fatal if swallowed", "CORROSIVE to the eyes", "CORROSIVE to the skin", "DO NOT get on skin, eyes or clothing, "Avoid inhaling the vapour" and "Handle Thymovar in a well-ventilated area@ have been included in the Precautions section of the secondary display panel of the general label. Furthermore, the product label instructs applicators to wear chemical resistant gloves, long protective clothing and eye goggles or a face shield when handling Thymovar.

The Thymovar product label requires that all of the honey supers are removed prior to treatment and that the product be applied before the honey flow or after all surplus honey has been removed. Additionally, the label also instructs beekeepers not to extract honey from treated combs of the brood chambers in the following spring.

Next Steps

Before making a final registration decision on thymol, the PMRA will consider all comments received from the public in response to this consultation document. The PMRA will accept written comments on this proposal up to 45 days from the date of publication of this document. Please forward all comments to Publications. The PMRA will then publish a Registration Decision, which will include its decision, the reasons for it, a summary of comments received on the proposed final decision and the Agency's response to these comments.

Other Information

When the PMRA makes its registration decision, it will publish a Registration Decision on thymol (based on the Science Evaluation of Proposed Registration Decision PRD2010-18, Thymol). In addition, the test data referenced in this consultation document will be available for public inspection, upon application, in the PMRA's Reading Room (located in Ottawa).