Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb

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Pest Management Regulatory Agency
30 December 2016
ISSN: 1925-0967 (PDF version)
Catalogue number: H113-27/2016-25E-PDF (PDF version)

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To obtain a full copy of Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb please contact our publications office.

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Summary

Table of Contents

Background

This document forms part of a wider assessment of health and environmental risks of the active ingredients used in antisapstain and joinery wood treatments.

In 2004, Health Canada’s Pest Management Regulatory Agency (PMRA) completed a re-evaluation of the occupational risks for the antisapstain uses of three antisapstain active ingredients: 2-(thiocyanomethylthio) benzothiazole (TCMTB), copper-8-quinolinolate (copper-8), and disodium octaborate tetrahydrate (boron). The occupational exposure and risk assessments were conducted for workers at lumber processing facilities such as sawmills. The re-evaluation decision (RRD2004-08) identified the need for additional data to refine the occupational risk assessments and required that a product stewardship program (with follow-up monitoring) be implemented for all registered antisapstain chemicals to reduce exposure to workers. In addition, RRD2004-08 indicated that an assessment of the environmental risks of antisapstain products would be communicated in separate documents.

In response to the 2004 decision, the registrants of antisapstain products, the Sapstain Industry Group, developed a product stewardship program, referred to as the Exposure Reduction Program (ERP). This program was approved by PMRA, implemented for all antisapstain products and follow-up occupational exposure field monitoring was conducted. The ERP included additional personal protective equipment and engineering controls, which have shown to be effective in reducing worker exposure.

There are currently five active ingredients registered as joinery wood preservatives. These active ingredients are: boron, didecyl dimethyl ammonium chloride (DDAC), iodocarb, propiconazole and tebuconazole. Considering that the occupational exposure scenarios for antisapstain and joinery uses are similar, and in the interest of efficiencies and consistency in decision making, occupational risk assessments were also conducted for all joinery products using the Sapstain Industry Group’s follow-up field monitoring exposure data.

Altogether, seven active ingredients registered as antisapstain and/or joinery wood preservatives required updated health and environmental risk assessments. These active ingredients are: TCMTB, copper-8-quinolinolate, boron, DDAC, iodocarb, propiconazole, and tebuconazole. The occupational risk assessments for these seven antisapstain and joinery active ingredients have been updated using current use information, current toxicology endpoints and the follow-up field monitoring exposure data. The environmental risk assessments have been conducted using available data and information.

This document addresses the health and environmental risk assessments for the antisapstain and joinery uses of iodocarb. The re-evaluation of the antisapstain and joinery uses of the remaining active ingredients listed above will be communicated in separate documents.

Overview

Proposed Re-evaluation Decision for Antisapstain and Joinery Uses of Iodocarb

The PMRA has completed the health and environmental risk assessments for the antisapstain and joinery uses of iodocarb. Under the authority of the Pest Control Products Act, the PMRA is proposing continued registration of the antisapstain and joinery uses of iodocarb in Canada.

An evaluation of available scientific information found that the antisapstain and joinery uses of iodocarb products are not expected to pose risks of concern to human health or the environment when used according to the proposed revised label directions. As a requirement for the continued registration of antisapstain and joinery products containing iodocarb, new risk-reduction measures are proposed.

This proposal affects the joinery and antisapstain end-use products containing iodocarb registered in Canada. Once the final re-evaluation decision is made, the registrant will be instructed on how to address any new requirements.

Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb is a consultation document that summarizes the science evaluation for iodocarb 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 in Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb 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 iodocarb.

The PMRA will accept written comments Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb proposal up to 90 days from the date of publication of PRVD2016-25. Please forward all comments to Publications.

What Does Health Canada Consider When Making a Re-evaluation 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 of, or exposure to, the product under its conditions or proposed conditions of registration. Conditions of registration may include special precautionary measures on the product label to further reduce risk. The Act also requires that products have value when used according to the label directions.

To reach its decisions, the PMRA applies hazard and risk assessment methods as well as policies that are rigorous and modern. These methods consider the unique characteristics of potentially sensitive subpopulations in both humans (for example, children) and 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 present when predicting the impact of pesticides. For more information on how the PMRA regulates pesticides, the assessment process and risk-reduction programs, please visit the Pesticides and Pest Management section of Health Canada’s website.

For more details on the information presented in this summary, please refer to the Science Evaluation of Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb.

What is Iodocarb?

Iodocarb is an antimicrobial active ingredient registered for preservation of joinery wood products and as a sapstain control chemical. In addition to its uses as an antisapstain and for joinery, iodocarb is registered in Canada as a preservative in various materials (textiles, adhesives, caulks, paints, latex paper coating, plastic, water-based inks, metal working fluids) and a variety of consumer products (including household cleaning products).

Antisapstain products are wood preservatives used to prevent the growth of staining fungi in freshly cut lumber. They are applied to freshly-cut wood by dipping or spraying to achieve short-term (months) protection against staining fungi.

Wood products that have been manufactured into items such as windows and doors are referred to as joinery or millwork. These items are often used in above-ground settings where they are subject to moderate decay conditions. For this reason, wooden windows and doors are typically protected with a joinery wood preservative to prevent the growth of decay fungi and increase the service life. Unlike antisapstain treatments, which are applied to lumber for short-term protection against aesthetic damage, joinery preservatives provide long-term decay protection to wood that does not require the degree of protection provided by heavy-duty wood preservation.

Health Considerations

Can Approved Uses of Iodocarb Affect Human Health?

Antisapstain and joinery products containing iodocarb are unlikely to affect your health when used according to revised label directions.

Potential exposure to 3-iodo-2-propanyl butyl carbamate (iodocarb) may occur through the dermal and inhalation routes, when handling and applying antisapstain and joinery products containing iodocarb or by handling the treated wood. When assessing health risks, two key factors are considered:

  • the levels at which no health effects occur in animal testing 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.

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 health effects noted in animals occur at doses more than 100-times higher (and often much higher) than levels to which humans are normally exposed when pesticide-containing products are used according to label directions.

In laboratory animals, iodocarb was slightly toxic via the oral and inhalation routes, of low acute dermal toxicity, a severe eye and mild dermal irritant, and did not cause an allergic skin reaction.

Registrant-supplied short-, and long-term (lifetime) animal toxicity tests were assessed for the potential of iodocarb to cause neurotoxicity, immunotoxicity, chronic toxicity, cancer, reproductive and developmental toxicity, and various other effects. The most sensitive endpoints for risk assessment were reproductive and developmental effects (decreased survival and developmental retardation). The risk assessment protects against the above-noted effects by ensuring that the level of human exposure is well below the lowest dose at which these effects occur in animal tests.

Risks in Residential and Other Non-Occupational Environments

Non-occupational risks are not of concern.

There are currently no registered residential uses of iodocarb antisapstain or joinery products. As such, a risk assessment for a residential handler was not required.

Occupational Risks to Mixer/Loader/Applicator and Postapplication Workers

Occupational risks are not of concern when used according to the revised label directions.

Health risks to handlers are not of concern for all scenarios. Based on the updated personal protective equipment (PPE) required as a result of the Exposure Reduction Program (ERP) for Antisapstain Chemicals (see Section 3.4.3 of Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb), health risk estimates associated with mixing, loading, and applying activities and during handling of treated wood exceeded target dermal margins of exposure (MOEs) and are not of concern. Inhalation exposure was shown to be very low for the majority of workers and is mitigated by the use of a NIOSH-respirator for specific job tasks where there is potential for inhalation exposure, as described in the ERP. Current product labels that do not include all of the required elements of the personal protective equipment will be updated to conform to the ERP.

Postapplication risks are not of concern.

Postapplication exposure through contact with dried wood is not anticipated as antisapstains are designed to prevent the growth of staining fungi in freshly cut lumber during storage and transit and not for long-term wood protection in residential or commercial areas. Similarly, exposure to consumers from contact with treated wood is also considered to be minimal.

Joinery wood is intended for use in millwork, window and door frames and other above ground non structural decorative exterior wood such as soffits and fascia. Significant human exposure is not expected for this type of wood.

No health risks of concern were identified for workers handling freshly treated wood (wet or dry) in the sawmill. Since this type of exposure is expected to be greater than for workers or bystanders handling treated wood or joinery products after they have left the sawmill, postapplication health risks are not of concern.

Environmental Considerations

What Happens When Iodocarb Is Introduced Into the Environment?

When used as an antisapstain according to the revised label directions, iodocarb is not expected to pose risks of concern to the environment.

Antisapstains, such as iodocarb, may enter the environment if newly treated wood is exposed to rain. Iodocarb may reach the aquatic environment if any rainwater containing the chemical is permitted to run-off from the treatment facility and its wood storage areas into nearby waterbodies. Very little exposure to land organisms and their habitats is expected.

Iodocarb breaks down quickly in the presence of water at high pH but does not break down at low pH. In the presence of microbes, iodocarb breaks down quickly in water and soil, forming propargyl butyl carbamate, which breaks down rapidly. Iodocarb is expected to be mobile to very mobile in mineral soils; however, because iodocarb breaks down quickly, it is not expected to enter groundwater. Residues of iodocarb are not expected to be found in air and are not expected to accumulate in the tissues of organisms. Iodocarb is toxic to freshwater and marine fish, aquatic invertebrates, and amphibians, if they are exposed to high enough levels. A conservative risk assessment indicated a potential risk to aquatic organisms. However, considering the conservative nature of the assessment and the required mitigation, the risks are considered acceptable.

Value Considerations

What is the Value of Iodocarb in Antisapstain Treatment?

Iodocarb is one of several active ingredients currently registered in Canada for use in antisapstain products. Antisapstain products are wood preservatives used to prevent the growth of staining fungi in freshly cut lumber. These pigmented fungi consume the readily available sugars and starches as they grow throughout the sapwood. While these sapstain fungi do not reduce the strength of the wood, the aesthetic damage done can result in significant economic losses in terms of the lumber being unmarketable or reduced in value.

What is the Value of Iodocarb in Joinery Treatment?

Iodocarb is one of five active ingredients currently registered in Canada for use in joinery products. Joinery products are wood preservatives used to treat products that have been machined or milled, such as window frames or doors. While these window frames and doors tend to be sheltered from excessive rains, they are still susceptible to fungal decay. Treatment with joinery products containing iodocarb inhibits the growth of decay fungi and extends the service life of wooden joinery components.

Proposed Measures to Minimize Risk

Labels of registered pesticide products include specific instructions for use. Directions include risk-reduction measures to protect human health and the environment. Following these directions is required by law. As a result of the re-evaluation of the antisapstain and joinery uses of iodocarb, the PMRA is proposing further risk-reduction measures in addition to those already identified on iodocarb product labels.

Additional Key Risk Reduction Measures

Human Health

To protect workers, additional general hygiene statements and personal protective equipment are required on all iodocarb antisapstain and joinery product labels conforming to the ERP.

Environment

To minimize the amount of iodocarb entering aquatic environments, wood treatment facilities using iodocarb antisapstains are to be equipped with drip pads (where wood is allowed to sit for a short drying period immediately after treatment) that are roofed and paved.

Precautionary label statements are required to identify environmental hazards and prevent run-off from treatment facilities to waterbodies.

Next Steps

Before making a final re-evaluation decision on the antisapstain and joinery uses of iodocarb, the PMRA will consider any comments received from the public in response to Proposed Re-evaluation Decision PRVD2016-25, Antisapstain and Joinery Uses of Iodocarb. A science-based approach will be applied in making a final decision on iodocarb. 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 response to these comments.

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