Mr. Speaker, the response is as follows:
(a) Health Canada’s Pest Management Regulatory Agency (PMRA) committed to undertake a priority review of the turf uses of 2,4 D and other lawn care pesticides as part of its “Action Plan on Urban Use Pesticides”, announced in 2000 by the Minister of Health in response to public concerns regarding the safe use of these products in urban settings. The publication “Action Plan on Urban Use Pesticides” (http://www.pmra arla.gc.ca/english/pdf/hlawns/hl ActionPlan e.pdf) includes additional details of the plan.
PMRA’s general re evaluation process is outlined in the publication “PMRA Re evaluation Program” (DIR2001 03). The scientific assessment of 2,4 D would not have differed if it had been completed under the new Pest Control Products Act. Health Canada’s Pest Management Regulatory Agency has been routinely using the modern risk assessment methods enshrined in the new Act in its current reviews of both new and older chemicals. These modern risk assessment methods include an aggregate assessment that takes into account pesticide exposure from all sources, including food, water and pesticide use in homes and schools, and considers cumulative effects of pesticides that act in the same way. Also, the sensitivities of vulnerable groups such as infants and children are considered, and extra safety factors are applied to protect children.
PMRA’s assessment was conducted by its highly qualified scientists. The re evaluation of lawn and turf uses of 2,4 D was based on a comprehensive review of the considerable information available on 2,4 D, including:
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an extensive proprietary database including laboratory animal studies to determine potential health effects and studies that examine potential effects on the environment;
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published scientific information; these include reports, epidemiological studies and all other relevant scientific information published in scientific journals and other publicly available documentation;
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foreign reviews results of other countries scientific assessments of 2,4 D including the United States, the European Union, New Zealand and the World Health Organization; and,
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use pattern information collected by the PMRA
The broad range of scientific information examined by the PMRA included relevant data utilized by non regulatory groups, such as the Ontario College of Family Physicians in their April 2004 report. That report focussed on a subset of epidemiology studies from the public literature, but the authors did not have all available data to conduct a human health risk assessment. The examination of animal toxicity data from internationally accepted guideline studies using doses well above those to which humans are typically exposed to, combined with exposure data obtained from well designed studies, is currently the best methodology available for assessing risks to human health.
For 2,4 D, external experts were also asked to comment on various aspects of PMRA’s review in order to provide a broader perspective on the assessment than the usual internal review process. This 5 member science advisory panel included experts in their fields of epidemiology, exposure assessment, human toxicology, and environmental toxicology. The Ppnel generally agreed with the PMRA’s assessment. A summary of the panel’s findings and recommendations was included in the public consultation document “Proposed Acceptability for Continuing Registration” (PACR2005 01), Re evaluation of Lawn and Turf Uses of (2,4 Dichlorophenoxy) acetic Acid [2,4 D]”.
The PMRA will carefully consider the numerous comments received in response to PACR2005 01, revise the assessment as required, and communicate the final decision to the public in a re-evaluation decision document as soon as the process is completed.
(b) As part of the re evaluation of the lawn and turf uses of 2,4 D, the PMRA took into account the toxic substances management policy and followed its Rrgulatory directive DIR99 03. The former is the federal government policy that directs the determination and management of Track 1 substances (chemicals that are toxic, persistent, bioaccumulative and anthropogenic) and is consistent with the Canadian Environmental Protection Act. Polychlorinated dioxins substituted in at least the 2,3,7,8 positions are track 1 substances.
In 1982, Agriculture Canada's Pesticide Division (now Health Canada’s PMRA) had randomly collected from the marketplace forty one (41) 2,4 D amine end products and seventeen (17) 2,4 D ester end products for testing of dioxins. Of these fifty eight (58) samples, only six 2,4 D amines and one 2,4 D ester end products were contaminated with either dichlorodioxin or trichlorodioxin at levels marginally higher than 10 ppb (parts per billion parts of 2,4 D), the production limit established in Agriculture Canada’s Pesticides Division Trade Memo R 1 216 published in April 15, 1983. 2,3,7,8 TCDD was not detected at limit of detection of 1 ppb. To demonstrate that today’s products do not contain Track 1 substances such as dioxins, above the level of quantification, the PMRA is requiring the manufacturers to submit data of 2,3,7,8 TCDD and 2,3,7,8 TCDF and their respective higher substituted chlorinated congeners to the limits of quantitation (0.1 ppb) in five recent batches of all technical products as part of the data requirements from the re evaluation of 2,4 D.
(c) It is important to distinguish between toxicity data (studies that are specifically designed to elicit a toxic effect) and exposure data (monitoring and biomonitoring data in humans such as in workers & bystanders including children and the elderly that occur as a result of normal use). Since its inception, the PMRA has not used toxicity studies in humans for risk assessment in which human subjects are intentionally dosed with pesticides to identify or quantify their effects. Human studies of this nature that have been brought to our attention, have been used solely in a supplementary manner thus far, to confirm that the animal model is an appropriate surrogate for assessment purposes. As such, the PMRA does not condone the use of human subjects for pesticide testing to establish no observed adverse effect levels (see below) for assessing risk for new or existing products. However, the PMRA does evaluate monitoring and biomonitoring data in humans (e.g., exposure data from workers, bystanders, victims of accidents), if available.
The PMRA uses animal data as a surrogate for understanding the hazard profile (i.e., toxicity) of a given chemical and for establishing reference doses for the purpose of conducting human health risk assessments. Toxicity data from a number of different mammalian species including mice, rats, rabbits and dogs are examined, in order to assess cross species similarities and differences, as well as species sensitivity. Studies examine short and long term effects, as well as the potential for a chemical to induce birth defects, reproductive effects, potential sensitivity in the young and cancer. These studies are conducted at doses many times higher than what humans are exposed to, in order to understand the toxicity profile for a given chemical. Typically, the most sensitive species is used as the indicator species for human toxicity and health risk assessment, unless there are sufficient data to indicate another species is more appropriate. For human health risk assessment, safety factors are applied to the dose where no effects were observed in animal studies (i.e. the “no effect level” noted above) to create a reference dose. This reference dose is, at minimum, 100 times below the dose where no toxic effects were observed in animal tests. The safety factors account for interspecies extrapolation from animals to humans, for intraspecies variability, as well as for any other concerns identified in the toxicology data such as potential sensitivity of the young. This approach is consistent with that of other regulatory authorities that base human health risk assessments on animal toxicity data. Retrospective analyses indicate that this approach is protective of the human population.
The amount of exposure to humans from all relevant routes (oral, inhalation, absorption through the skin) and pathways (dietary intake, drinking water, residential exposures) is determined using a variety of data. Demographic data obtained from survey information are used to generate gender and age specific profiles for body weight, food consumption and activity patterns. This includes data on infants, toddlers, youth and adult sub populations. The demographic data are combined with the amount of pesticide residue present in air, drinking water, food and treated areas such as turf. As an example, the unique physiology, behaviours and play habits of children, such as their body weight and hand to mouth contact while playing on treated grass are considered together, when determining how much exposure they encounter. Residue data are obtained from a variety of sources including environmental surveillance, food residue monitoring programs and from both published and unpublished scientific studies designed to assess residue transfer to humans that may result from contact with treated areas. To be protective of human health, conservative estimates are used to obtain upper bound exposure levels. A listing of published human exposure studies considered specifically in the 2,4 D turf re evaluation is provided in PACR 2005 01.
The PMRA then conducts a quantitative risk assessment in order to integrate the results of the hazard assessment with those of an exposure assessment. This means that the level of exposure (or dose) that an individual, including a child, may encounter from a specific pesticide is compared to the reference dose that is established from the toxicity data. In the case of 2,4 D use on lawns, the PMRA required that the level of exposure to various sub populations be at least 300 to 1000 times below the dose where no toxic effects were observed in animal tests. Thus, the amount of 2,4 D to which humans are exposed through diet, drinking water and contacting treated grass is 100s to 1000s of times less than the dose that causes any toxic effect in animal studies.
(d) The information note clearly invites stakeholders to provide any additional information that may be relevant to the re evaluation. As indicated earlier, PMRA’s review did determine that 2,4 D does not pose unacceptable risks for lawn and turf use when label directions are followed, and proposed the continuing registration of 2,4 D products. The public has responded to PACR2005 01 with numerous comments, some of which include additional published data and information. After a thorough evaluation of all comments received during the comment period, the PMRA will revise the assessment as required and communicate the final decision to all stakeholders in a re-evaluation decision document and a revised Information Note .
