21 May 2010
HC Pub: 100240
ISBN: 978-1-100-15729-0 (print version)
ISBN: 978-1-100-15860-0 (PDF version)
Catalogue number: H113-9/2010-12E (print version)
Catalogue number: H113-9/2010-12E-PDF (PDF version)

Summary

Table of Contents

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

Proposed Registration Decision for Oxalic Acid Dihydrate

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 Oxalic Acid Dihydrate Technical and Oxalic Acid Dihydrate, containing the technical grade active ingredient oxalic acid dihydrate to control Varroa mites in honeybee colonies.

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 PRD2010-12, Oxalic Acid Dihydrate, provides detailed technical information on the human health, environmental and value assessments of Oxalic Acid Dihydrate Technical and Oxalic Acid Dihydrate.

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 oxalic acid dihydrate, 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 oxalic acid dihydrate, 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 PRD2010-12, Oxalic Acid Dihydrate of this consultation document.

What Is Oxalic Acid Dihydrate?

Oxalic acid dihydrate is a dicarboxylic acid, which is a relatively strong organic acid. Oxalic Acid Dihydrate is used in honeybee colonies to control Varroa mites using two different application methods, as a solution by the trickle treatment method, and as a solid by the vaporisation method. Applications are made in the late fall to early spring, when little to no brood is present in the hive and honey supers are not in place.

While the mode of action of Oxalic Acid Dihydrate is not entirely understood, it appears to be mainly due to the low pH of the acid, which results in contact toxicity (physical injury of mites due to low pH). With the trickle-method of application, Oxalic Acid Dihydrate is dissolved into a 1:1 sugar:water solution, which is directly applied to the infested bees. The bees can tolerate the concentration of oxalic acid in the applied solution, but the Varroa mites cannot. With the vaporisation method of application, Oxalic Acid Dihydrate crystals are heated using a specialized application device until they liquefy and vaporise. Oxalic acid vapour fills the hive and all the bees and hive interior surfaces are covered with a very thin layer of Oxalic Acid Dihydrate crystals. While these fine crystals are tolerated by the bees, they are toxic to the Varroa mites.

Health Considerations

Can Approved Uses of Oxalic Acid Dihydrate Affect Human Health?

Oxalic Acid Dihydrate is unlikely to affect your health when used according to label directions.

Exposure to oxalic acid dihydrate may occur when handling and applying the end-use product, Oxalic Acid Dihydrate. 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.

Since the technical grade active ingredient, oxalic acid dihydrate, is highly acutely toxic and corrosive to both the eye and skin, the statements, "DANGER - POISON", "DANGER - CORROSIVE TO EYES", and "DANGER - SKIN IRRITANT" have been included on the principal display panel of the general label and AFatal or poisonous if swallowed", "DO NOT get in eyes", "CORROSIVE to the eyes", "DO NOT get on skin or clothing", "Corrosive to the skin", and "Avoid inhaling/breathing dust or fumes@ have been included in the PRECAUTIONS section of the secondary display panel of the general label.

Residues in Water and Food

Dietary risks from food and water are not of concern.

It is anticipated that the amount of oxalic acid dihydrate present as a residue after application of the end-use product will not likely exceed the range of naturally occurring concentrations found in honey or vegetables. The direct application of oxalic acid dihydrate to beehives means that exposure to sources of drinking water will be negligible. Therefore, the use of oxalic acid dihydrate is not expected to result in dietary risk from food and/or water.

Occupational Risks From Handling Oxalic Acid Dihydrate

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

Pesticide applicators handling and applying Oxalic Acid Dihydrate to bee hives, can come in direct contact with oxalic acid dihydrate on the skin and in the eyes, as well as by accidental ingestion and inhalation. The current label statements adequately mitigate the concern of exposure to the applicators.

It is expected that only workers will be permitted access to the treated areas, thus the potential for bystander exposure is expected to be minimal and not of concern.

Environmental Considerations

What Happens When Oxalic Acid Dihydrate Is Introduced Into the Environment?

Oxalic acid is a naturally occurring compound that transforms rapidly under environmental conditions. Exposure of the chemical to the environment is expected to be limited during the use of Oxalic Acid Dihydrate for control of Varroa mite in beehives. The product is applied as a liquid or vapour to an affected colony; environmental exposure would occur primarily through spillage or leakage during application. Based on limited exposure, the chemical's natural occurrence and the likelihood for relatively rapid transformation under environmental conditions, the proposed use of Oxalic Acid Dihydrate is not expected to pose a significant risk to the environment. Therefore, further review of the environmental chemistry, fate, and toxicology of Oxalic Acid Dihydrate was not considered necessary.

Value Considerations

What Is the Value of Oxalic Acid Dihydrate?

Oxalic Acid Dihydrate has value for control of Varroa mite in honeybee colonies. Evaluated data demonstrated that Oxalic Acid Dihydrate can provide 90-99% control of Varroa mites in honeybee colonies when either the trickle treatment or vaporisation application methods are used when little to no honeybee brood is present in the hives (i.e. late fall to early spring).

Measures to Minimize Risk

Labels of registered pesticide products include specific instructions for use. Directions include risk-reduction measures measures to protect human and environmental health. These directions must be followed by law.

The key risk-reduction measures being proposed on the labels of Oxalic Acid Dihydrate Technical and Oxalic Acid Dihydrate to address the potential risks identified in this assessment are as follows.

Key Risk-Reduction Measures

Human Health

Because there is a possibility of accidental oral, dermal, and inhalation exposure by workers, individuals should observe all precautionary and first aid statements on the product label. The label-required wearing of personal protective equipment by workers and the requirement to conduct activities in well ventilated areas are expected to minimize the potential for exposure to oxalic acid dihydrate. Based on the limited use pattern to bee hives, bystanders are not expected to be exposed to oxalic acid dihydrate.

Environment

No environmental risk-reduction measures are required. Standard label statements to protect the environment are required.

Next Steps

Before making a final registration decision on oxalic acid dihydrate, 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 oxalic acid dihydrate (based on the Science Evaluation of Proposed Registration Decision PRD2010-12, Oxalic Acid Dihydrate). 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).