Proposed Registration Decision PRD2020-11, Silicon Dioxide (Present as 100% Diatomaceous Earth), DX13 Dust, and DX13 Industrial

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Pest Management Regulatory Agency
26 June 2020
ISSN: 1925-0886 (PDF version)
Catalogue number: H113-9/2020-11E-PDF (PDF version)

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Summary

Table of Contents

Proposed registration decision for silicon dioxide (present as 100% diatomaceous earth), DX13 Dust and DX13 Industrial

Health Canada’s Pest Management Regulatory Agency (PMRA), under the authority of the Pest Control Products Act, is proposing registration for the sale and use of Celatom Food Grade Diatomaceous Earth, DX13 Dust, and DX13 Industrial, containing the active ingredient silicon dioxide (present as 100% diatomaceous earth), to control spider mites on greenhouse tomatoes, cucumbers, and peppers, cannabis produced commercially indoors and indoor ornamental plants and plantscapes.

Silicon dioxide is currently registered as an insecticide and acaricide for both indoor and outdoor commercial and domestic uses. DX13 Dust and DX13 Industrial are currently registered for structural use, including bedframes and mattresses, and outdoor use to kill various insect pests. For details, see Proposed Acceptability for Continuing Registration Document, PACR2004-09, Silicon Dioxide and Silica Gel, and Registration Decision Document, RDD2004-20, Silicon Dioxide and Silica Gel.

An evaluation of available scientific information found that, under the approved conditions of use, the health and environmental risks and the value of the pest control products are acceptable.

This summary describes the key points of the evaluation, while the Science Evaluation of Proposed Registration Decision PRD2020-11, Silicon Dioxide (Present as 100% Diatomaceous Earth), DX13 Dust, and DX13 Industrial provides detailed technical information on the human health, environmental and value assessments of silicon dioxide (present as 100% diatomaceous earth), and the end-use products DX13 Dust, and DX13 Industrial.

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. 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:

Before making a final registration decision on silicon dioxide (present as 100% diatomaceous earth), DX13 Dust, and DX13 Industrial, Health Canada’s PMRA will consider any comments received from the public in response to PRD2020-11. Health Canada will then publish a Registration Decision on silicon dioxide (present as 100% diatomaceous earth), DX13 Dust, and DX13 Industrial, which will include the decision, the reasons for it, a summary of comments received on the proposed registration decision and Health Canada’s response to these comments.

For more details on the information presented in this summary, please refer to the Science Evaluation of PRD2020-11.

What is silicon dioxide (present as 100% diatomaceous earth)?

Silicon dioxide is a mineral substance that is found in diatomaceous earth and is the active ingredient in DX13 Dust and DX13 Industrial. It physically damages the water-proof exoskeleton of arthropods, causing them to lose water and die of dehydration.

Health considerations

Silicon dioxide (present as 100% diatomaceous earth) is unlikely to affect human health when it is used according to label directions.

Potential exposure to silicon dioxide (present as 100% diatomaceous earth) may occur through the diet (food and water) or when handling and applying the product. When assessing health risks, two key factors are considered:

The levels used to assess risks are established to protect the most sensitive human population (for example, children and nursing mothers). As such, sex and gender are taken into account in the risk assessment. Only uses for which the exposure is well below levels that cause no effects in animal testing are considered acceptable for registration.

Toxicology studies in laboratory animals describe potential health effects from varying levels of exposure to a chemical and identify the dose where no effects are observed.

The technical grade active ingredient, Celatom Food Grade Diatomaceous Earth containing silicon dioxide (present as 100% diatomaceous earth), is considered to be of low acute toxicity, via the oral, dermal and inhalation routes, minimally irritating to the eyes and skin and not likely to be a dermal sensitizer. Silicon dioxide has a history of use as an insecticide and is permitted as a food additive in Canada.

In laboratory animals, DX13 (Diatomaceous Earth), a toxicological equivalent to DX13 Dust, was of low acute inhalation toxicity and practically non-irritating to the eye. Considering surrogate studies and published scientific literature on the active ingredient, DX13 Dust is of low acute toxicity via the oral, dermal and inhalation routes, practically non-irritating to the eye, non-irritating to the skin, and not expected to be a dermal sensitizer. DX13 Dust is a respiratory irritant. No toxicology studies were submitted for the end-use product, DX13 Industrial, but supported rationales argued that its effects on animals would be similar to those of DX13 Dust.

Residues in water and food

Dietary risks from food and water are acceptable.

Residues of silicon dioxide (present as 100% diatomaceous earth) on treated food crops are possible at the time of harvest. Due to its low toxicity profile and its history of use as a food additive, consumer exposure to silicon dioxide present in DX13 Dust and DX13 Industrial is not expected to pose a health risk when the end-use products are applied as directed by the label. In addition, the likelihood of silicon dioxide (present as 100% diatomaceous earth) residues in drinking water will be low. Consequently, health risks are acceptable for all segments of the population, including infants, children, adults and seniors.

Risks in residential and other non-occupational environments

Estimated risk for residential and other non-occupational exposure is acceptable.

DX13 Dust and DX13 Industrial are registered for use in commercial and residential areas. DX13 Dust and DX13 Industrial are proposed for use on greenhouse tomatoes, cucumbers and peppers, indoor plants and plantscapes and cannabis produced commercially indoors. The product labels will include measures to prevent bystander exposure such as reducing dust/spray drift, restricting access to the treated area until dusts have settled or sprays have dried and ensuring that applicators limit DX13 Dust and DX13 Industrial to target areas and remove any residues on non-target surfaces. Residential and non-occupational exposure to DX13 Dust and DX13 Industrial is therefore expected to be low when label directions are observed. Consequently, the risk to residents and the general public is acceptable.

Occupational risks from handling DX13 Dust and DX13 Industrial

Occupational risks are acceptable when DX13 Dust and DX13 Industrial are used according to the label directions, which include protective measures.

Workers handling DX13 Dust and DX13 Industrial can come into direct contact with silicon dioxide (present as 100% diatomaceous earth) through inhalation and contact with eyes and skin. To protect workers from exposure to DX13 Dust and DX13 Industrial, the labels require workers to wear long-sleeved shirts, long pants, chemical-resistant gloves, socks and shoes, and protective eyewear during loading, application, clean-up and repair, as well as a dust mask during handling (including clean-up and repair) and a respirator for loading and application. A restricted-entry interval of 4 hours, or until dusts have settled or sprays have dried, is prescribed for all uses. If early entry is necessary during the restricted-entry interval, workers must wear a long-sleeved shirt, long pants, chemical-resistant gloves, socks and shoes, protective eyewear (goggles or face shield) and a dust mask. For use on cannabis produced commercially indoors, greenhouse tomatoes, cucumbers and peppers, an information sheet is required for DX13 Dust or DX13 Industrial stating personal protective equipment (PPE) and re-entry requirements for post-harvest clean-up activities. Workers involved in post-harvest clean-up activities will be required to wear a long-sleeved shirt, long pants, chemical-resistant gloves, socks and shoes, protective eyewear (goggles or face shield) and a dust mask and re-entry without PPE is not permitted until dusts have settled and the area cleaned.

The occupational risks are acceptable when the precautionary statements on the label are observed.

Environmental considerations

What happens when silicon dioxide (present as 100% diatomaceous earth) is introduced into the environment?

When Celatom Food Grade Diatomaceous Earth and its associated end-use products, DX13 Dust and DX13 Industrial, are used according to the label, the risks to the environment are acceptable.

Silicon dioxide is a naturally occurring inert substance that is composed primarily of silica, the same major component of quartz and sand. It is an insecticide with a non-toxic mode of action, interfering with the water balance of insects by absorbing protective coatings (oils and fats) and via mechanical abrasion of the outer cuticle layer.

As an insecticide, silicon dioxide (present as 100% diatomaceous earth) may harm bees and other beneficial insects used in greenhouse production. Label instructions will include requirements to avoid application when bees or other beneficial insects are in the treatment area. Due to its non-toxic mode of action and inert nature, silicon dioxide (present as 100% diatomaceous earth) is expected to be non-toxic to other non-target organisms. When silicon dioxide (present as 100% diatomaceous earth) is used in accordance with the label and the required precautions, the resulting environmental risk is acceptable.

Value considerations

What is the value of DX13 Dust and DX13 Industrial?

DX13 Dust and DX13 Industrial provide a new mode of action for control of spider mites on plants grown indoors.

Applied to provide coverage of all plant surfaces, DX13 Dust and DX13 Industrial control spider mites on greenhouse tomatoes, peppers, and cucumbers, cannabis produced commercially indoors, and indoor ornamental plants and plantscapes. For all of those uses, these products provide a new active ingredient with a new physical mode of action, to which resistance is unlikely.

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 labels of Celatom Food Grade Diatomaceous Earth, DX13 Dust and DX13 Industrial to address the potential risks identified in this assessment are as follows.

Key risk-reduction measures

Human health

The statement, ‘KEEP OUT OF REACH OF CHILDREN AND PETS’ is required on the principal display panel and in the PRECAUTIONS section of the secondary display panel of the DX13 Dust and DX13 Industrial labels.

Standard hazard and precautionary statements are required on the end-use product labels. Workers will be required to wear a long-sleeved shirt, long pants, chemical-resistant gloves, socks and shoes and protective eyewear during loading, application, clean-up and repair, as well as a dust mask during handling (including clean-up and repair) and a respirator for loading and application.

There will be a restricted-entry interval of 4 hours, or until dusts have settled or sprays have dried. If early entry is necessary during the restricted-entry interval, workers must wear a long-sleeved shirt, long pants, chemical-resistant gloves, socks and shoes, protective eyewear (goggles or face shield) and a dust mask.

For use on cannabis produced commercially indoors, greenhouse tomatoes, cucumbers and peppers, an information sheet is required to protect workers from dusts disturbed during post-harvest activities.

Application of DX13 Dust and DX13 Industrial will not be permitted on cannabis, or the surrounding soil, past the vegetative stage.

Additional statements have been added to the label to address post-application exposure in residential and commercial areas.

Environment

Label statement indicating that the product is toxic to bees and other beneficial insects used in greenhouse production.

Next steps

Before making a final registration decision on ingredient silicon dioxide (present as 100% diatomaceous earth), DX13 Dust, and DX13 Industrial, Health Canada’s PMRA will consider any comments received from the public in response to PRD2020-11. Health Canada will accept written comments on this proposal up to 45 days from the date of publication of PRD2020-11. Please forward all comments to Publications. Health Canada will then publish a Registration Decision, which will include its decision, the reasons for it, a summary of comments received on the proposed decision and Health Canada’s response to these comments.

Other information

When the Health Canada makes its registration decision, it will publish a Registration Decision on silicon dioxide (present as 100% diatomaceous earth), DX13 Dust, and DX13 Industrial (based on the Science Evaluation of PRD2020-11). In addition, the test data referenced in PRD2020-11 will be available for public inspection, upon application, in the PMRA’s Reading Room (located in Ottawa).

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