Proposed Re-evaluation Decision: Alkyl Dimethyl Benzyl Ammonium Chloride Cluster (ADBAC)

26 June 2008
ISBN: 978-1-100-10055-5 (978-1-100-10056-2)
Cat. No.: H113-27/2008-23E (H113-27/2008-23E-PDF)
(PRVD2008-23)

Table of Contents

• Overview
  • What Is the Proposed Re-evaluation Decision?
  • What Does Health Canada Consider When Making a Re-evaluation Decision?
  • What Is ADBAC?
  • Health Considerations
  • Environmental Considerations
  • Measures to Minimize Risk
  • Next Steps
    
    
• Science Evaluation
• 1.0 Introduction
  
  
• 2.0 The Technical Grade Active Ingredients, Their Properties and Uses
  • 2.1 Identity of the Technical Grade Active Ingredients
  • 2.2 Physical and Chemical Properties of the Technical Grade Active Ingredient
  • 2.3 Comparison of Use Patterns in Canada and the United States
    
    
• 3.0 Impact on Human Health and the Environment
  • 3.1 Human Health
    • 3.1.1 Occupational Exposure and Risk Assessment
    • 3.1.2 Non-Occupational Exposure and Risk Assessment
    • 3.1.3 Cumulative Effects
      
      
  • 3.2 Environment
    • 3.2.1 Environmental Risk Assessment
    • 3.2.2 Toxic Substances Management Policy Considerations
      
      
• 4.0 Proposed Re-evaluation Decision
• 5.0 Data Required as a Condition of Continued Registration
• 6.0 Supporting Documentation
  
  
• List of Abbreviations

Overview

What Is the Proposed Re-evaluation Decision?

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

An evaluation of available scientific information found that products containing ADBAC 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 ADBAC uses, new risk-reduction measures must be included on the labels of all products. No additional data are being requested at this time.

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

This Proposed Re-evaluation Decision is a consultation document¹ that summarizes the science evaluation for ADBAC 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 ADBAC.

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.

ADBAC cluster, a group of 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 (e.g. the federal Toxic Substances Management Policy [TSMP]).

Based on the health and environmental risk assessments published in a 2006 RED, the USEPA concluded that ADBAC 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 in this consultation document.

What Is ADBAC?

ADBAC is a broad spectrum biocide. It is registered in Canada under the authority of the Pest Control Products Act for the control of algae, bacteria, fungi, viruses and molluscs at the following use sites: swimming pools, empty food storage areas (e.g. potato), indoor hard surfaces (e.g. sinks, countertops, musical instrument mouthpieces, garbage pails, shower stalls), other indoor surfaces/water (e.g. upholstery, carpets, closed toilet systems, humidifiers), industrial process fluids (e.g. pulp and paper mill systems, open cooling water tower systems, air washers, industrial scrubbing systems/recirculating water cooling towers and wastewater systems), material (e.g. textiles, leather) and wood.

Wood uses of ADBAC are not included in this re-evaluation.

Health Considerations

Can Approved Uses of ADBAC Affect Human Health?

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

People could be potentially exposed to ADBAC working as a mixer/loader/applicator or if in contact with treated material. 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 population group (e.g. 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 ADBAC 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 ADBAC Is Introduced Into the Environment?

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

Certain aquatic organisms could be exposed to ADBAC in the environment. Environmental risk is assessed by the risk quotient method--the ratio of the estimated environmental concentration to the relevant effects endpoint of concern. The resulting risk quotients are compared to corresponding levels of concern. A risk quotient less than the level of concern is considered a negligible risk to non-target organisms, whereas a risk quotient greater than the level of concern indicates some degree of risk.

The USEPA concluded that the reregistration of ADBAC was acceptable provided risk-reduction measures to further protect the environment were implemented. These conclusions apply to the Canadian situation, and equivalent risk-reduction measures are required.

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 ADBAC, the PMRA is proposing further risk-reduction measures for product labels.

Human Health

• Additional protective equipment to protect mixers/loaders/applicators as well as instructions regarding maximum use rate in pulp and paper process and maximum yearly applications for once-through cooling water tower use
• Additional advisory label statements and a restricted-entry interval to protect swimmers
• Additional advisory label statements and phase-out of residential humidifier uses to protect consumers

Environment

• Additional advisory label statements
• Instructions regarding maximum yearly applications for once-through cooling water tower use

Next Steps

Before making a final re-evaluation decision on ADBAC, the PMRA will consider all comments received from the public in response to this consultation document. The PMRA will then publish a Re-evaluation Decision² 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.

Science Evaluation

1.0 Introduction

ADBAC is a group of biocides registered in Canada for use against algae, bacteria, fungi, viruses and molluscs. Following the re-evaluation announcement for ADBAC, the registrant of the technical grade active ingredient in Canada indicated its intention to provide continued support for all uses included on the labels of commercial and domestic end-use products in Canada.

The PMRA used recent assessments of ADBAC from the United States Environmental Protection Agency (USEPA). The USEPA Reregistration Eligibility Decision (RED) document for ADBAC, dated August 2006, as well as other information on the regulatory status of ADBAC in the United States can be found on the USEPA  Pesticide Registration Status page.

2.0 The Technical Grade Active Ingredients, Their Properties and Uses

2.1 Identity of the Technical Grade Active Ingredients

The Canadian ADBAC cluster is comprised of 10 chemicals that are structurally similar quaternary ammonium compounds.

Common name: ADBAC

Function: Biocide

Chemical family: Quaternary amines

Chemical name:

International Union of Pure and Applied Chemistry (IUPAC) N-alkyl dimethyl benzyl ammonium chloride

The table below provides information on each individual member of this cluster.

Table 1 Members of the ADBAC Cluster

CAS Number	Name	Structure	Chain Length
139-08-2	ADBAC*		R = 25% C12 60% C14 15% C16
Not available	ADBAC	Same as above	R = 40% C12 50% C14 10% C16
68956-79-6	ADBAC*		R = 50% C12 30% C14 17% C16 3% C18
Not available	ADBAC	Same as above	R = 68% C12 32% C14
68391-01-5	ADBAC		R = 5% C12 60% C14 30% C16 5% C18
68391-01-5	ADBAC	Same as above	R = 67% C12 25% C14 7% C16 1% C18
Not available	ADBAC*	Same as above	R = 3% C12 95% C14 2% C16
63449-41-2	ADBAC	Same as above	R = 61% C12 23% C14 11% C16 5% C18
Not available	Di-alkyl methyl benzyl ammonium chloride		R = 5% C12 60% C14 30% C16 5% C18
121-54-0	Diisobutylphenoxy ethoxyethyl dimethyl benzyl ammonium chloride

* These active ingredients were not included in this re-evaluation.

Although these technical active ingredients are registered, no end-use product containing N-alkyl (25% C12, 60% C14, 15% C16) dimethyl ethylbenzyl ammonium chloride, N-alkyl (50% C12, 30% C14, 17% C16, 3% C18) dimethyl benzyl ammonium chloride, or N-alkyl (3% C12, 95% C14, 2% C16) dimethyl benzyl ammonium chloride is currently registered in Canada. Therefore, these three chemicals are not included in the re-evaluation.

Based on the manufacturing process, the products are not expected to contain impurities of human health or environmental concern as identified in Regulatory Directive DIR98-04, Chemistry Requirements for the Registration of a Technical Grade of Active Ingredient or an Integrated System Product, Section 2.13.4 or Toxic Substances Management Policy (TSMP) Track 1 substances as identified in Regulatory Directive DIR99-03, The Pest Management Regulatory Agency's Strategy for Implementing the Toxic Substances Management Policy, Appendix II.

2.2 Physical and Chemical Properties of the Technical Grade Active Ingredient

Property Result

Vapour pressure 38 mm Hg

UV-visible spectrum Not expected to absorb at λ > 300 nm (λ max = 208 nm)

Solubility in water Soluble in water

2.3 Comparison of Use Patterns in Canada and the United States

ADBAC is a group of biocides registered in Canada for use against algae, bacteria, fungi, viruses and molluscs in the following use sites: swimming pools, empty food storage area (e.g. potato), indoor hard surfaces (e.g. sinks, countertops, musical instrument mouthpieces, garbage pails, shower stalls, other indoor surfaces/water/air (e.g. upholstery, carpets, closed toilet systems, humidifiers), industrial process fluids (e.g. pulp and paper mill systems, open cooling water tower systems, air washers, industrial scrubbing systems/recirculating water cooling towers and wastewater systems), material (e.g. textiles and leather), and wood.

Twenty-nine technical, 24 manufacturing concentrate, 47 commercial, and 123 domestic products containing ADBAC are currently registered in Canada. Most of the end-use products are formulated as a solution, with two formulated as a pressurized product and one as a solid product. ADBAC products are added directly to water in industrial process fluids, swimming pools, laundries and humidifiers or diluted in water to treat hard non-porous surfaces in institutional, commercial, industrial and residential settings by immersion, wiping, mopping, trigger spray or low- or high-pressure spray. The ready-to-use products are applied directly on the site to be treated.

Appendix I lists all ADBAC products registered as of April 2008 under the authority of the Pest Control Products Act.

ADBAC products are widely used and have a large number of use patterns. The USEPA's strategy was to use representative scenarios for each use site to typify the wide variety of ADBAC uses. The risk assessment discussed in the RED was thus performed on a number of representative scenarios believed to provide high-end degrees of dermal, inhalation or incidental ingestion exposure.

The American and Canadian use patterns were compared. Except for the textile and leather preservative uses (maximum rate: 10 g a.i./kg material treated), all Canadian uses are encompassed by the American uses. Nonetheless, the potential risk associated with the textile and leather preservation use can be extrapolated from certain American uses that have similar exposures. Therefore, based on this comparison of use patterns, it was concluded that the USEPA RED for ADBAC is an adequate basis for the re-evaluation of Canadian uses.

It should be noted that certain uses of ADBAC are regulated under the Food and Drugs Act and are not included in this assessment. However, these uses were assessed by the USEPA. The uses are as follows:

• disinfectant
• commercial sanitizer in food manufacturing/processing plants and areas in which food is prepared or kept (e.g. food processing equipment, food utensils and drinking glasses)

In addition, ADBAC was granted temporary registration in 2002 for use as a heavy-duty wood preservative. Currently, the PMRA is reviewing the submission to convert the status to full registration. The results of the review will be published when completed. Therefore, this assessment does not include the re-evaluation of the heavy-duty wood preservative use.

3.0 Impact on Human Health and the Environment

In its 2006 RED, the USEPA concluded that the end-use products formulated with ADBAC met the safety standard under the American Food Quality Protection Act and would not pose unreasonable risks or adverse effects to humans and the environment if used according to the amended product labels.

3.1 Human Health

Toxicology studies in laboratory animals describe potential health effects resulting from various levels of exposure to a chemical and identify dose levels at which no effects are observed. Unless there is evidence to the contrary, it is assumed that effects observed in animals are relevant to humans and that humans are more sensitive to effects of a chemical than the most sensitive animal species.

In Canada, exposure to ADBAC may occur by using the product, working as a mixer/loader/applicator or contacting the treated material. When assessing health risks, the PMRA considers two key factors: 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 population group (e.g. children and nursing mothers).

3.1.1 Occupational Exposure and Risk Assessment

Occupational risk is estimated by comparing potential exposures with the most relevant endpoint from toxicology studies being used to calculate a margin of exposure (MOE). This is compared to a target MOE incorporating safety factors protective of the most sensitive population group. If the calculated MOE is less than the target MOE, it does not necessarily mean that exposure will result in adverse effects, but mitigation measures to reduce risk would be required.

Workers can be exposed to ADBAC when mixing, loading or applying the pesticide and when handling treated material. In Canada, the use sites include industrial processes and water systems, commercial/institutional/industrial premises and swimming pools.

3.1.1.1 Occupational Handler Exposure and Risk

No dermal endpoint for systemic effects was selected for ADBAC because no systemic effects were identified. Therefore, the USEPA did not assess the occupational risk for the dermal route of exposure. The irritation effect of ADBAC was mitigated by personal protective equipment (PPE) requirements already listed on labels. The level of PPE required was based on the toxicity of the end-use product.

Several inhalation exposure scenarios for handlers were identified in the RED. Among those, the following were considered relevant to the Canadian situation:

• liquid pour
• mopping
• wiping
• low-pressure handwand
• liquid/metering pump
• high-pressure/high-volume spray and medium-pressure spray

Maximum application rates as stated on the product labels, surrogate unit exposure values from the Chemical Manufacturers Association antimicrobial exposure study and the Pesticide Handlers Exposure Database, and the USEPA estimates of daily amount handled/treated were used in the assessment.

The duration of exposure evaluated in the USEPA assessment included short- and intermediate-term exposures. The USEPA reported acceptable MOEs (i.e. greater than target MOE of 100) for all occupational inhalation exposure scenarios ranging from 360 to 31 000, except for the following:

• pulp and paper, liquid pump
• once-through cooling water with high flow streams, metered pump
• small process water systems, liquid pour

To mitigate the risks for occupational handlers in pulp and paper mills, the USEPA required that the maximum application rate be reduced from 20.5 kg a.i./tonne of paper to 7.0 kg a.i./tonne of paper with the use of a metering pump system (a closed system). To mitigate the risks for occupational handlers in once-through cooling water towers, the USEPA required that the maximum number of applications be four per year using a metering pump system (closed system). The USEPA required that a dust mist respirator be used when applying the product containing ADBAC to small process water systems in order to mitigate the inhalation risk at these work locations.

The RED adequately addressed potential occupational exposure scenarios associated with the relevant Canadian uses of products containing ADBAC. Therefore, conclusions derived from the RED are considered applicable to the Canadian uses that are encompassed by those of the United States.

The PMRA also requires that the Canadian use rate in the pulp and paper manufacturing process not exceed 7.0 kg a.i./tonne of paper and that the product be applied with a metered pump.

For the once-through cooling water tower use, the PMRA requires that the maximum number of applications be limited to four per year. Canadian products can also be applied manually. Since the USEPA assessment of occupational risk via inhalation was based on a metering pump application system, the PMRA requires that a respirator be worn when products are applied manually.

For small process water systems, the United States required that a dust mist respirator be used when applying the product. Considering that no occupational risks were assumed for the metered pump scenario, the PMRA requires that either a dust mist respirator be worn or a metered pump be used when applying the product to the water systems. The maximum Canadian use rate in small process water systems (60 ppm) is higher than that assessed in the RED (40 ppm) for the metered pump method. Nonetheless, the USEPA assessment resulted in MOEs well above the target (6200 for short-term exposure and 5200 for intermediate-term exposure) and thus provides sufficient protection to account for the difference in application rates between the United States and Canada.

In Canada, workers may also be exposed to ADBAC while handling the product for commercial treatment of textiles and leather. Although this scenario was not specifically discussed in the RED, the process by which the ADBAC antimicrobial treatment would be added to the textile or leather manufacturing process is similar to other "liquid pour" or "metering pump" scenarios assessed by the USEPA. Based on use information, the amount handled per day in a textile plant is likely to be similar to the amount used for small water process systems and the PMRA requires that a respirator be worn when applying the product, unless a metering pump is used.

The USEPA did not recommend protective equipment for dermal exposure since it did not conduct an occupational dermal risk assessment. In Canada, not all end-use products currently require PPE. As a good hygiene practice, the PMRA requires that, as a minimum, chemical-resistant gloves, long pants, a long-sleeved shirt, shoes and socks be worn by workers handling liquid concentrates. Proposed label amendments are listed in Appendix II.

3.1.1.2 Postapplication Exposure and Risk

The USEPA determined that occupational postapplication dermal and inhalation exposures associated with the above scenarios were negligible.

The RED adequately addressed exposure scenarios associated with the Canadian uses of ADBAC, and conclusions derived from the RED are considered applicable to the Canadian situation. Based on this, the PMRA requires no further mitigation measures with respect to occupational postapplication exposures.

3.1.2 Non-Occupational Exposure and Risk Assessment

3.1.2.1 Residential Exposure

Residential exposure is estimated using the MOE approach described in Section 3.1.1.

Homeowners can be exposed to ADBAC when mixing or applying the pesticide and when exposed to the treated material. Toddlers can be exposed via "hand-to-mouth" activities and through inhalation.

3.1.2.1.1 Residential Handlers

In Canada and the United States, ADBAC is registered as an antimicrobial for use in swimming pools and on indoor surfaces, such as hard floors, carpets, walls, bathroom fixtures, musical instrument mouthpieces, trash cans, toilet bowls, and as a liquid laundry additive. In addition, ADBAC is registered in the United States for a number of outdoor uses such as decorative ponds and fountains, and ornamental plants and lawns. Since these uses are not registered in Canada, their risk assessments are not discussed in this document.

Among the potential dermal and inhalation exposure scenarios assessed in the RED for handler risks in residential settings, the following scenarios are considered relevant to the Canadian situation:

• indoor hard surfaces (mopping, wiping)
• swimming pools (liquid pour)
• recreational vehicle (RV) holding tanks (liquid pour)*

* Note that RV holding tank use is not registered in Canada. It is included here because this use is considered to be representative of applications to humidifiers and musical instruments.

Residential handlers were assumed to apply products without using personal protective equipment. Dermal and inhalation unit exposure values from the surrogate data, maximum application rates from the representative product labels and the USEPA-estimated quantities of active ingredient handled/treated per day were used in the RED.

The USEPA concluded that residential handlers were exposed to ADBAC on a short-term (1-30 day) basis because the tasks were assumed to be episodic and homeowners were unlikely to use solely ADBAC products for varying activities.

For all scenarios, MOEs were greater than the target MOEs, ranging from 820 to 50 000 for inhalation exposure (target MOE = 100), and 72 to 54 000 for dermal exposure (target MOE = 10). Therefore, the risks did not exceed the USEPA's level of concern.

The RED adequately addressed potential exposure scenarios associated with the Canadian residential handler. Thus, the conclusions derived from the RED are considered applicable to the Canadian situation. Based on this, the PMRA requires no further mitigation measures with respect to residential handler exposure. It is recommended that residential handlers wear rubber gloves when handling the products as a good hygiene practice.

3.1.2.1.2 Residential Postapplication Exposure

In Canada, potential postapplication exposure could result from uses of ADBAC on/in hard surfaces, carpets, textiles, humidifiers, swimming pools and musical instrument mouthpieces.

Among the scenarios chosen by the USEPA to represent high-end exposure, the following are considered relevant to the Canadian situation:

• crawling on treated hard surfaces and carpets (dermal and incidental oral exposure to children)
• wearing treated clothing (dermal exposure to adults and children and incidental oral exposure to children)
• swimming in treated pools (adult and child incidental ingestion)
• using treated musical instrument mouthpieces and reeds (adult and child incidental oral exposure)
• using portable humidifiers (adult and child inhalation exposure)

For the first three scenarios, the calculated dermal and inhalation MOEs were above the target MOEs of 10 and 100, respectively. Therefore, the risks were not of concern to the USEPA.

The RED recommended a 15-minute restricted-entry interval and requested that the statement "DO NOT apply when swimmers are in the immediate vicinity" be included on label.

The RED adequately addressed potential exposure scenarios associated with the Canadian residential uses of ADBAC on treated floors and carpets and in swimming pools. Thus, the conclusions derived from the RED for these exposure scenarios are considered applicable to the Canadian situation. To further protect swimmers, the USEPA's label statement to prohibit application when swimmers are around and its recommendation for a 15-minute restricted-entry interval will also be required on the Canadian labels.

Canadians can be exposed to the use of ADBAC in laundries in hospitals, nursing homes and diaper plants. The potential exposure scenarios were adequately addressed in the RED through the residential uses of ADBAC as a laundry additive. The conclusions derived from the RED are considered applicable to the Canadian situation.

In Canada, adults and children may also be exposed to ADBAC residues in clothing as a result of commercial treatment of textiles and leather. Although this scenario was not specifically discussed in the RED, the process by which textiles are treated commercially is similar to residential laundering of clothing. The USEPA assessment of risk from exposure to clothing residues in residential laundry use can be applied to the Canadian commercial treatment scenario by using the commercial rate. Based on this, exposure to residue on clothing from commercial treatment of textiles with ADBAC is not of concern.

The USEPA did not have residue data to assess oral exposures to children and adults from treated musical instruments. In Canada, there is only one product registered for this use. It is formulated as a liquid and is diluted to a 600 ppm ADBAC solution for sanitizing wind instruments. The risk from oral exposure to ADBAC-treated musical instruments is considered negligible based on the following rationale.

• The treated musical instruments are to be rinsed with tap water before use.
• The application rate is half the maximum rate used for food bottling and packaging in the United States.
• The potential risk from exposure to treated food packaging was assessed by the USEPA, and the result was much below the USEPA's level of concern.

Therefore, no further mitigation measures are required for this use.

In both Canada and the United States, ADBAC can be used in humidifiers to control the buildup of bacteria and algae in water tanks. The USEPA used the Multi-Chamber Concentration and Exposure Model (MCCEM) to estimate the potential inhalation risk to adults and children.

The MCCEM is designed to calculate average/peak indoor air concentrations of chemicals released from products or materials in residences and estimate inhalation exposure to these chemicals for both acute and chronic scenarios. Information on the type of residence, zone volumes, interzonal air flow rates, air exchange rates, the pollutant emission rate and occupant activity pattern are input into the model.

The resulting MOEs were below the target MOE of 100. Therefore, the risk was of concern to the USEPA. The eight-hour MOEs for adults and children were 71 and 11, respectively, and the 24-hour MOEs for adults and children were 10 and 4, respectively. As there are no available mitigation measures for the humidifier use, the USEPA determined that the residential use of ADBAC in humidifiers was not eligible for reregistration.

The RED adequately addressed potential exposure scenarios associated with the Canadian residential uses of ADBAC in humidifiers. ADBAC uses in humidifiers in Canada are very similar to the use assessed in the RED and conclusions derived by the USEPA are applicable. The use of ADBAC in residential humidifiers is of concern and should be phased out unless additional data are provided to refine the assessment. This includes uses in portable humidifiers as well as furnace humidifiers.

Five products are currently registered in Canada with humidifier uses.

3.1.2.2 Aggregate Risk Assessment

3.1.2.2.1 USEPA Assessment

The assessment of aggregate risk combines the different routes of exposure (i.e. from food, water and residential exposures).

Two key factors were considered by the USEPA when selecting exposure scenarios for incorporation into the aggregate assessment: the use patterns of the products and the probability of co-occurrence. Typically, the acute and chronic aggregate risk assessments address the combined risks from the direct and indirect food contact uses and drinking water exposure only. However, since an endpoint representing a single dose effect was not identified in the database for ADBAC, an acute aggregate risk assessment was not conducted.

Tier 1 screening computer models were used to generate screening level estimates of drinking water concentrations. These estimates were based on the American highest label seasonal rate (338 kg a.i./ha, three applications/year) and were used to assess the chronic aggregate risk. The chronic aggregate exposure constituted 3.5% and 10.3% of the chronic population adjusted dose for adults and children, respectively, and was not of concern to the USEPA.

Short- and intermediate-term aggregate risk assessments assumed contributions from food, drinking water and non-occupational exposure (dermal, inhalation, incidental ingestion). In the RED, the following exposure scenarios were considered to likely co-occur on a short-term base.

Adults

• chronic dietary
• applying cleaning products via mopping, wiping and trigger pump spray (dermal, inhalation)
• wearing treated clothing (dermal)

Children

• chronic dietary
• after cleaning products are applied to carpets (oral ingestion, dermal)
• wearing treated clothing (oral ingestion, dermal)

The oral, dermal and inhalation routes of exposures were not aggregated because the ADBAC toxicological endpoints for these three routes were based on different toxic effects. Rather the risks from the co-occurrence of the same routes of exposure were aggregated. Moreover, aerosol inhalation exposure to ADBAC used in humidifiers was not included in the aggregate risk assessment since the risk was of concern and was addressed separately.

For all the routes of exposure considered in the RED, the short-term aggregate MOEs were greater than the target MOEs for both adults and children; therefore, risks were not of concern.

3.1.2.2.2 Canadian Scenario

As the Canadian use pattern is less than that of the United States (e.g. no turf and ornamental uses), the Canadian potential aggregate exposure scenarios were adequately addressed by the USEPA aggregate risk assessment.

3.1.3 Cumulative Effects

The USEPA has not determined whether ADBAC has a common mechanism of toxicity with other substances or whether it shares a toxic metabolite produced by other substances. Therefore, it was assumed that ADBAC does not share a common mechanism of toxicity with other substances and a cumulative risk assessment was not required.

3.2 Environment

3.2.1 Environmental Risk Assessment

ADBAC is hydrolytically stable under abiotic and buffered conditions over the pH 5-9 range. However, based on a biodegradation study, the USEPA concluded that ADBAC readily degrades into 60% carbon dioxide in 13 days. The soil mobility study indicated that ADBAC is immobile in soil. ADBAC was not expected to pose a concern for bioconcentration in aquatic organisms.

ADBAC is primarily used as an indoor antimicrobial in residential, commercial/institutional/industrial and public facilities. The USEPA concluded that the indoor uses of ADBAC were not likely to result in an unacceptable ecological risk to non-target organisms based on minimal exposure potential. Therefore, quantitative risk assessments for these uses were not required.

In the United States, ADBAC can be used on ornamental plants and shrubs, residential lawns and commercial turf and golf courses, and in puddles, ornamental ponds and pools. In addition, ADBAC can be used in the United States for non-pressure treatment (antisapstain) of wood. These uses could result in potential terrestrial or aquatic exposures and effects. However, since these uses are not registered in Canada, they are not considered in this document.

The USEPA decided that the once-through cooling water tower use has potential for direct release of ADBAC into aquatic systems.

To assess the ecological risk of ADBAC to aquatic organisms resulting from the once-through cooling water tower use, the USEPA calculated risk quotients based on appropriate toxicity endpoints and expected environmental concentrations, and compared the resulting risk quotients to corresponding levels of concern.

Exposure was estimated using a screening level computer model. An average-sized plant on small, average and large rivers was used in the modelling, and downstream chemical concentrations from a chemical discharge were calculated assuming a constantly changing flow rate.

The screening level assessment indicated that continuous dosing of ADBAC to once-through cooling water systems located on low-flow streams would result in the highest concentration of the pesticide in the receiving water. High water flow and intermittent dosing had less impact on aquatic organisms than medium to low stream flow. However, levels of concern for all aquatic animals were triggered even at the lowest dosage modelled (2.0 ppm) using a continuous method regardless of the water flow rate.

Terrestrial wildlife was not expected to be impacted from the once-through cooling water tower use.

In order to reduce the environmental risk, the USEPA required that uses for the once-through cooling water towers be limited to no more than four times per year. In addition, all labels supporting this use were required to include statements indicating that discharge of effluent containing ADBAC into aquatic systems be prohibited unless permit requirements were met and the permitting authorities were notified in writing. Directions for bentonite clay treatment (to deactivate ADBAC) were also to be provided. Bentonite clay was found to be an effective agent in reducing the amount of ADBAC in effluent/runoff due to its strong tendency to bind to ADBAC.

The American use pattern for ADBAC in once-through cooling water towers encompasses the Canadian use pattern. Consequently, the USEPA's risk-reduction measures for ADBAC in oncethrough cooling water towers are applicable to the Canadian situation. These measures include:

• a maximum of four applications per year
• additional effluent discharge statements as well as environmental hazard statements
• a requirement for deactivation of ADBAC in effluent by bentonite clay before discharge

Label amendments are described in detail in Appendix II.

3.2.2 Toxic Substances Management Policy Considerations

The management of toxic substances is guided by the 1995 federal Toxic Substances Management Policy, which puts forward a preventive and precautionary approach to deal with substances that enter the environment and could harm the environment or human health. The policy provides decision makers with direction and sets out a science-based management framework to ensure that federal programs are consistent with its objectives. One of the key management objectives is virtual elimination from the environment of toxic substances that result predominantly from human activity and that are persistent and bioaccumulative. These substances are referred to in the policy as Track 1 substances.

The federal Toxic Substances Management Policy and PMRA Regulatory Directive DIR99-03, The Pest Management Regulatory Agency's Strategy for Implementing the Toxic Substances Management Policy, were taken into account during the re-evaluation of ADBAC. The PMRA has reached the following conclusions.

• ADBAC was found to be hydrolytically stable under abiotic and buffered conditions over the pH 5-9 range in aquatic environments (half-lives: 150-379 days) and stable to photodegradation in pH 7 buffered aqueous solutions. However, other information reported in the RED indicates rapid microbial degradation of ADBAC.
• ADBAC substances are not expected to be bioaccumulative. Maximum bioconcentration in freshwater fish was 33 fold for edible tissues, 160 fold for non-edible tissues and 79 fold for whole fish tissues. Therefore, ADBAC active ingredients are not candidates for Track 1 classification.
• Based on a review of the available chemistry information (see Section 2.1), the technical products are not expected to contain impurities of toxicological concern as identified in Regulatory Directive DIR98-04 or TSMP Track 1 substances as identified in Regulatory Directive DIR99-03, Appendix II.

Formulant issues are being addressed through PMRA formulant initiatives and Regulatory Directive DIR2006-02, Formulants Policy and Implementation Guidance Document, published on 31 May 2006.

4.0 Proposed Re-evaluation Decision

The PMRA has determined that ADBAC is acceptable for continued registration with the implementation of the proposed risk-reduction measures. These measures are required to further protect human health and the environment. The labels of Canadian end-use products must be amended to include the statements listed in Appendix II. A submission to implement label revisions will be required within 90 days of finalization of the re-evaluation decision. No additional data are being requested at this time.

In addition, the residential humidifier use is to be phased out unless additional data are provided to refine the assessment.

For ADBAC end-use products that contain other active ingredients under re-evaluation, the reviews for these active ingredients will be included in separate documents.

5.0 Data Required as a Condition of Continued Registration

Registrants of ADBAC in the United States have agreed to conduct an inhalation exposure study that would allow refinement of the risk assessment for humidifier use.

Should Canadian registrants wish to add humidifier use to the label in the future, the same study should be included in the submission data package.

6.0 Supporting Documentation

PMRA documents, such as Regulatory Directive DIR2001-03 and DACO tables, can be found on our website at www.pmra-arla.gc.ca. PMRA documents are also available through the Pest Management Information Service. Phone: 1-800-267-6315 within Canada or 1-613-736-3799 outside Canada (long distance charges apply);
fax: 613-736-3798;
e-mail: pmra_infoserv@hc-sc.gc.ca.

The federal TSMP is available through  Environment Canada's website.

The USEPA RED document for ADBAC is available on the  USEPA Pesticide Registration Status page.

List of Abbreviations

λ

wavelength

ADBAC

alkyl dimethyl benzyl ammonium chloride cluster

a.i.

active ingredient

bw

body weight

CAS

Chemical Abstracts Service

DACO

data code

g

gram(s)

kg

kilogram(s)

MCCEM

Multi-Chamber Concentration and Exposure Model

mm Hg

millimetre(s) mercury

MOE

margin of exposure

nm

nanometre(s)

pH

-log10 hydrogen ion concentration

PMRA

Pest Management Regulatory Agency

PPE

personal protective equipment

ppm

parts per million

PRVD

Proposed Re-evaluation Decision

RED

Reregistration Eligibility Decision

RV

recreational vehicle

TSMP

Toxic Substances Management Policy

USEPA

United States Environmental Protection Agency

¹"Consultation statement" as required by subsection 28(2) of the Pest Control Products Act.

²"Decision statement" as required by subsection 28(5) of the Pest Control Products Act.