Consultation Document on Carbofuran, Proposed Re-evaluation Decision PRVD2009-11

This consultation is now closed.

31 July 2009
HC Pub: 8348
ISBN: 978-1-100-13227-3 (print version)
ISBN: 978-1-100-13228- (PDF version)
Catalogue number: H113-27/2009-11E (print version)
Catalogue number: H113-27/2009-11E-PDF (PDF version)

To obtain an electronic copy of the document, Proposed Re-evaluation Decision PRVD2009-11, Carbofuran, please contact publications@hc-sc.gc.ca.

Should you require further information please contact the Pest Management Information Service.

Summary

Table of Contents

• What Does Health Canada Consider When Making a Re-evaluation Decision?
• Regulatory Status in Organisation for Economic Cooperation and Development Countries
• What Is Carbofuran?
• Health Considerations
• Environmental Considerations
• Value Considerations
• Measures to Minimize Risk
• What Additional Scientific Information Is Requested?
• Next Steps
• Other Information

After a re-evaluation of the insecticide carbofuran, Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the Pest Control Products Act, is proposing phase out of carbofuran products in Canada.

An evaluation of available scientific information found that, under the current conditions of use, carbofuran products pose an unacceptable risk to human health and the environment, and therefore do not meet Health Canada's current standards for human health and environmental protection. As a result, all uses of carbofuran are proposed for phase-out. This includes registered uses on canola, mustard, sunflower, corn (sweet, field and silage), sugar beet, green pepper, potato, raspberry and strawberry as well as temporary emergency uses on turnip and rutabaga. The emergency uses on turnip and rutabaga were registered for the period of April 1, 2008, to August 31, 2008, and are no longer registered for use in Canada, but were included at the time of this assessment.

The PMRA's pesticide re-evaluation program considers potential risks as well as the 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. Re-evaluation draws on data from registrants, published scientific reports, information from other regulatory agencies, and any other relevant information available.

The proposal affects all end-use products registered in Canada that contain carbofuran. This Proposed Re-evaluation Decision is a consultation document that summarizes the science evaluation for carbofuran and presents the reasons for the proposed re-evaluation decision.

The information in the Portable Document Format (PDF) version of this document 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 human health, environmental and value assessment of carbofuran.

The PMRA will accept written comments on this proposal up to 60 days from the date of publication of this document. 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 acceptable¹ 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 conditions or proposed conditions of registration. The Act also requires that products have value² 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 hazard and risk assessment methods as well as policies that are rigorous and modern. These methods consider the unique characteristics of sensitive subpopulations in both humans (for example, children) and organisms in the environment (i.e. 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 portion of Health Canada's website at healthcanada.gc.ca/pmra.

Carbofuran is one of the carbamate pesticides re-evaluated as outlined in the Re-evaluation Note REV2002-06, Re-evaluation of Selected Carbamate Pesticides. The PMRA has considered all currently available information regarding health and environmental risk, including reviews from the United States Environmental Protection Agency, as a source of information for conducting Canadian re-evaluation assessments.

Before making a final re-evaluation decision on carbofuran, the PMRA will consider all comments received from the public in response to this consultation document.³ The PMRA will then publish a Re-evaluation Decision⁴ on carbofuran, which will include the decision, the reasons for it, a summary of comments received on the proposed registration decision and the PMRA's response to these comments.

For more details on the information presented in this overview, please refer to the Science Evaluation section of the PDF version of this document.

Regulatory Status in Organisation for Economic Cooperation and Development Countries

The United States Environmental Protection Agency reviewed the safety and benefits of all uses of carbofuran and concluded that ecological and human health risks were of concern.

On May 15, 2009, the United States Environmental Protection Agency issued a final rule⁵ that it is revoking all of the existing carbofuran tolerences, referred to as maximum residue limits in Canada, on crops effective December 31, 2009, and will also move to cancel all remaining uses of carbofuran in the future.

What Is Carbofuran?

Carbofuran is a systemic, carbamate insecticide (Resistance Management Mode of Action group 1A), used to control a broad range of insect pests on certain field, vegetable and fruit crops. It is applied using conventional ground equipment to canola, mustard, sunflower, corn (sweet, field and silage), sugar beet, green pepper, potato, raspberry, strawberry, turnip and rutabaga and can also be applied by aerial equipment to corn (field, silage and sweet), canola and mustard. It may be applied by farmers, farm workers and professional applicators.

Health Considerations

Can Approved Uses of Carbofuran Affect Human Health?

Risks of concern to human health have been identified for both occupational and dietary carbofuran exposure.

Potential exposure to carbofuran may occur through diet (food and water) or when handling and applying the product. When assessing health risks, two key factors are considered:

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

Carbofuran was highly toxic via the oral route of exposure but was of low dermal toxicity in rats. Acute inhalation studies were not available. Carbofuran was a minimal eye irritant and was not a dermal sensitizer.

Acute overexposure to carbofuran can inhibit cholinesterase, an enzyme necessary for normal functioning of the nervous system. This can produce a variety of symptoms in animals and humans including ataxia, salivation, lacrimation, tremors and breathing difficulties. With carbofuran, cholinesterase inhibition can occur rather rapidly with exposure (within minutes) but rapidly recovers along with the cessation of any of the aforementioned cholinergic symptoms. To prevent overexposure, label directions must be followed.

There was no evidence that carbofuran was carcinogenic or teratogenic.An assessment of mutagenic potential in a variety of in vitro and in vivo genotoxicity studies showed that carbofuran has weak mutagenic properties in bacterial and mammalian cells. A cancer risk assessment was not required. The nervous system was the main target of toxicity in rats, rabbits and dogs. At higher dose levels, the male reproductive system of rats, rabbits and dogs also appear to be targeted by carbofuran. When carbofuran was given to pregnant animals, effects on the developing fetus were observed at doses that were greater than those that were toxic to the mother, indicating that the fetus is not more sensitive to carbofuran than the adult animal.

Residues in Food and Water

Dietary risks from food are of concern.

Reference doses define levels to which an individual can be exposed over a single day (acute) or lifetime (chronic) and expect no adverse health effects. Generally, dietary exposure from food and water is acceptable if it is less than 100% of the acute reference dose or chronic reference dose (acceptable daily intake). An acceptable daily intake is an estimate of the level of daily exposure to a pesticide residue that, over a lifetime, is believed to have no significant harmful effects.

Acute dietary exposure to carbofuran as a percentage of the acute reference dose ranges from 311% for youth aged 13 to 19 years to 1501% for children aged 1 to 2 years, and is 579% for the general population. The acute dietary exposure to carbofuran is higher than the acute reference dose for all population subgroups; therefore, it is of concern.

Chronic dietary exposure to carbofuran as a percentage of the acceptable daily intake ranges from 10% for females aged 13 to 49 years to 35% for children aged 1 to 2 years old, and is 14% for the general population. The chronic dietary exposure to carbofuran is less than the acceptable daily intake for all population subgroups; therefore, it is not of concern.

An aggregate risk assessment combining exposure from food and drinking water was not conducted, as exposure from food alone is of concern.

The Food and Drugs Act prohibits the sale of food containing a pesticide residue that exceeds the established maximum residue limit (MRL). Pesticide MRLs are established for food purposes through the evaluation of scientific data under the Pest Control Products Act. Each MRL value defines the maximum concentration in parts per million (ppm) of a pesticideallowed in/on certain foods. MRLs for carbofuran are currently established for carrots, onions, peppers, potatoes, rutabagas, turnips and strawberries. Where no specific MRL has been established, a default MRL of 0.1 ppm applies, which means that pesticide residues in a food commodity must not exceed 0.1 ppm. However, changes to this general MRL may be implemented in the future, as indicated in Discussion Document DIS2006-01, Revocation of 0.1 ppm as a General Maximum Residue Limit for Food Pesticide Residues [Regulation B.15.002(1)].

To protect the Canadian food supply and to mitigate dietary risks of concern, it is proposed that all MRLs for carbofuran be amended or revoked. Notwithstanding the general MRL of 0.1 ppm, the intent of this action to amend or revoke these MRLs is to prevent residues of carbofuran in or on foods. As noted above, changes to regulation B.15.002(1) may be implemented in future.

Risks in Residential and Other Non-Occupational Environments

Non-occupational risks are not of concern.

There are currently no residential uses of carbofuran. Given that homeowners would not be applying the product, a risk assessment for this scenario was not conducted.

Occupational Risks from Handling Carbofuran

Certain occupational mixer/loader/applicator risks are of concern.

Based on the precautions and directions for use on the product labels reviewed for this re-evaluation, risk estimates associated with certain mixing, loading and applying activities are of concern to the PMRA. All risk estimates for operators applying carbofuran by groundboom to turnips and rutabagas and by aircraft to corn did not reach the target margin of exposure and/or aggregate risk index, even with maximum personal protective equipment and engineering controls, and are therefore of concern.

Certain occupational postapplication risks are of concern.

Postapplication occupational risk assessments consider exposures to workers entering treated sites in agriculture. Based on the precautions and directions for use on the existing carbofuran product labels for the agricultural scenarios reviewed for this re-evaluation, postapplication risks to workers performing activities, such as thinning, pruning and harvesting of most crops, did not meet current standards and are of concern. The mitigation measures calculated to reduce postapplication risk may be agronomically unfeasible.

Environmental Considerations

What Happens When Carbofuran Is Introduced into the Environment?

Carbofuran poses a potential risk to terrestrial and aquatic organisms.

When carbofuran is released into the environment some of it can be found in soil and surface water. Carbofuran is highly mobile in soils and can therefore leach into groundwater and enter surface water in runoff. Carbofuran breaks down into several transformation products through hydrolysis, phototransformation and moderate biotransformation at rates that depend on environmental conditions. Hydrolysis is faster in water with a pH > 6 (basic conditions), with a half-life ranging from a few hours to 28 days. Carbofuran is stable to hydrolysis in acidic water (pH < 7). Phototransformation is fast in water, with a half-life of 6 days. Carbofuran is persistent in acidic soils (half life of 321 days) and moderately persistent in soils with a pH > 7 (half-life 149 days). Carbofuran is not expected to volatilize significantly and has a low potential for bioaccumulation in biota.

Carbofuran poses a risk to terrestrial and aquatic organisms. Birds and small wild mammals are at risk in and around the site of application due to the consumption of contaminated food items, and the risk cannot be mitigated.

Thirty three environmental incident reports from the United States and Canada were considered during the review of carbofuran, and indicated that exposure to carbofuran under the currently registered use pattern resulted in avian, small wild mammal and bee mortality.

Value Considerations

What Is the Value of Carbofuran?

For the control of some pests in agriculture, carbofuran is the only insecticide available, or there are few viable registered alternative products to carbofuran.

Carbofuran is absorbed by the host plant, providing a systemic mode of action in addition to contact action. It is effective in two ways:

• as a contact insecticide, killing target insects upon direct contact; and
• as an insecticide that works as a stomach poison, killing target insects upon ingestion of treated plants.

Being a systemic insecticide, carbofuran is absorbed and transported throughout the plant, imparting protection to the entire plant. Systemic insecticides are effective against insects with piercing-sucking mouthparts, such as leafhoppers, spittlebugs and tarnished plant bug, as the systemic insecticide moves within the vascular tissues and into plant cells where these pests feed.

As a systemic insecticide that acts upon ingestion, carbofuran is effective for the control of pests that otherwise could not be targeted by contact insecticides or non-systemic insecticides that act as a stomach poison, such as chewing insects, once they enter the host plants. For example, European corn borer larvae bore into the midrib of the leaf and migrate into the stalk of the plant or husk of the ear (corn), or feed inside the stems and fruit (pepper).

For canola, mustard, raspberry, strawberry and sugar beet as well as turnip and rutabaga (temporary uses), there are no registered (or viable) alternative active ingredients to carbofuran for the control of certain pests.

Measures to Minimize Risk

All products containing carbofuran are proposed for phase out because, based on available scientific information, they do not meet Health Canada's current standards for human health and environmental protection and pose unacceptable risks to human health and the environment. Additional mitigation measures are not being proposed at this time.

What Additional Scientific Information Is Requested?

The PMRA is seeking quantitative and/or qualitative information on the economic and social importance of carbofuran to specific industries and information on the availability and viability of alternative chemical and non-chemical pest management practices for the site and pest combinations registered for carbofuran. This information will allow the PMRA to refine sustainable pest management options for uses of carbofuran.

Next Steps

Before making a re-evaluation decision on carbofuran, Health Canada's Pest Management Regulatory Agency will consider all comments received from the public in response to this consultation. The PMRA will also consider quantitative and/or qualitative information on the economic and social importance of carbofuran to specific industries and information on the availability and viability of alternative chemical and non-chemical pest management practices for the site and pest combinations registered for carbofuran.

Health Canada's Pest Management Regulatory Agency will then publish a Re-evaluation Decision, which 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.

Once all carbamate pesticides have been re-evaluated, a cumulative risk assessment will be conducted, which will consider potential exposure to all chemicals with the same mechanism of toxicity. The results of the cumulative risk assessment may affect any previous re-evaluation decisions.

Other Information

When the re-evaluation decision is made, the PMRA will publish an Evaluation Report on carbofuran in the context of this re-evaluation decision (based on the Science Evaluation section of the PDF version of this document). In addition, the test data on which the decision is based will also be available for public inspection, upon application, in the PMRA's Reading Room (located in Ottawa, Ontario, Canada).

¹ "Acceptable risks" as defined by subsection 2(2) of the Pest Control Products Act

² "Value" as defined by subsection 2(1) of the Pest Control Products Act: "the product's actual or potential contribution to pest management, taking into account its conditions or proposed conditions of registration, and includes the product's (a) efficacy; (b) effect on host organisms in connection with which it is intended to be used; and (c) health, safety and environmental benefits and social and economic impact".

³ "Consultation statement" as required by subsection 28(2) of the Pest Control Products Act

⁴ "Decision statement" as required by subsection 28(5) of the Pest Control Products Act

⁵ Federal Register (Volume 74, Number 93) Rules and Regulations