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Chemicals Management Plan - Challenge Advisory Panel
Summary Report
January 11, 2008
Panel members present: Dr. T. Boadway (Chair), Dr. J. Bend, Dr. C. Brunk, Dr. N. Cherry, Dr. S. Findlay, Mr. G. Granville, Ms. L. Lusby, Dr. G. Muckle, Dr. D. Scott
Regrets: Dr. S. Maguire, Dr. J. Eyles
Outline:
The Challenge Advisory Panel meeting agenda was structured around key questions (see below) provided to the Panel for deliberation, open discussion and debate. Government staff members were present to make brief presentations, answer questions and clarify information. The questions presented concerned procedures and policies applied in the screening assessment determinations. At the end of the discussions, Panel members were asked to craft a response to each of the questions.
In the text below, the Government question is quoted in its entirety from the documents provided to the Panel.
Meeting Summary:
Welcome and Introductory Comments
The Chair welcomed all members and government staff and asked for a round table of introductions.
Before the questions were introduced, the Chair called for the development of a policy on Panel members being lobbied by other groups. A discussion followed, which resulted in the drafting of the official policy as follows:
"It is a policy of the Chemicals Management Plan Challenge Advisory Panel that all communications from stakeholders and requests for interviews from the news media be referred to the Chair of the Advisory Panel, Dr. Ted Boadway."
Panel Discussion
Question 1
In the context of the Challenge, a predisposition exists in relation to whether a substance that was considered a high priority for further action following categorization meets the definition of toxic under paragraph 64c of Canadian Environmental Protection Act (CEPA.) Specifically, the Ministers consider that where there is evidence that a substance for which the critical health effect is assumed to have no threshold of exposure for induction of effects - i.e., a genotoxic carcinogen - it is assumed that there is a probability of harm to human health at any level of exposure, and therefore indicates that the substance meets the criterion in paragraph 64c of CEPA 1999 (Ministers' Notice of Intent, December 9, 2006).
Consistent with the Ministers' Notice of Intent (December 9, 2006), Health Canada considers that evidence of carcinogenicity (i.e., classification by one or more international/national agencies), in the absence of a fully elucidated and accepted mode of action analysis supporting that there is a threshold of exposure for induction of effects, is sufficient to propose a conclusion that there is a probability of harm at any level of exposure and that the criterion in paragraph 64c of CEPA is met.
This approach is consistent with the approach taken for Priority Substances List assessments under CEPA. The rationale supporting this approach has been articulated (Health Canada, 1994)1; namely that it is considered inappropriate to specify a concentration or dose associated with a negligible or de minimis level of risk by low-dose extrapolation methodology, primarily since this would involve inclusion of considerations other than those based on science at this stage (i.e., making a societal judgment about what level constitutes de minimis risk). Unlike the in-depth Priority Substances List assessments, the nature of the Challenge screening assessments and associated timelines do not allow for in-depth weight of evidence analysis of mode of action, and therefore, the above-noted approach has been adopted.
Does the Panel agree that this approach constitutes appropriate application of precaution within the context of the Ministers' Challenge?
Considerations:
Forty-one of the 66 human health priorities in the Challenge were identified as carcinogens during the prioritization exercise.
Attachment:
Draft Screening Assessment Reports for naphthalene (CAS RN 91-20-3) and methyloxirane (CAS RN 75-56-9)
Panel Response to Question 1:
"The Panel supports the application of precaution as practiced by Health Canada for known genotoxic carcinogens.
Some members of the Panel supported the Ministry's approach on the appropriate application of precaution within the context of the Ministers' Challenge for the assessment of carcinogens with uncertain mode of action.
Other members of the Panel did not support this approach. Their view was that requiring a fully elucidated and accepted mode of action analysis before rejecting the hypothesis of a genotoxic mode of action is excessively precautionary."
Question 2
In Batch 1, 1,2-benzenediol and 1,4-benzenediol, are considered to meet the criterion in paragraph 64c on the basis of carcinogenicity as per the approach outlined above. However, the predominant source of general population exposure to these substances is expected to be as a result of their natural presence in various food and beverage items. Contributions to total exposure to the general population from the other media (ambient and indoor air, water and soil) from manufacturing and industrial uses are likely negligible in comparison.
For substances for which the critical effect is carcinogenicity and the predominant source of exposure to the general population is via naturally-occurring sources (e.g., the predominant source of general population exposure to 1,2-benzenediol is expected to be as a result of its natural presence in various food and beverage items) is it appropriately precautionary to adhere to the approach identified above?
Considerations:
Health Canada regulatory programmes do conduct risk assessments for substances for which naturally-occurring sources are a significant contributor to exposure (e.g., assessments of metals as Priority Substances under the Canadian Environmental Protection Act). In general, the focus of these assessments is on the inherent hazard of the substance itself, along with exposure from anthropogenic sources.
For substances which have undergone a screening assessment and have been found to meet the definition of 'toxic' under Section 64 of CEPA, the Act specifies that one of the following measures be proposed:
- taking no further action in respect of the substance;
- adding the substance to the Priority Substances List if a more in-depth assessment is required; or
- recommending that the substance be added to the List of Toxic Substances in Schedule 1 which would then necessitate a regulation or instrument respecting preventive or control actions in relation to a substance. Historically, the Ministers of Health and Environment have recommended in most cases that substances meeting the criteria of 'toxic' under Section 64 of CEPA be added to the List of Toxic Substances in Schedule 1.
Priority for risk management, under CEPA or other statutes, is informed by a number of considerations including outcome of comparing crude estimates of the potency of these substances with upper bounding exposure estimates; identification of controllable sources of exposure, including consideration of contribution of naturally-occurring sources; cost-benefit analyses, etc.
Attachment:
Draft Screening Assessment Report for 1,2-benzenediol (CAS RN 123-31-9)
Panel Response to Question 2:
"The Panel agrees that the approach outlined for substances where the predominant source of exposure is naturally occurring is appropriately precautionary."
Question 3
In the context of the Challenge, a predisposition exists in relation to whether a substance meets the definition of toxic under section 64(a) and/or (b) of CEPA. The predisposition is conditioned on current evidence that the substance is persistent, bioaccumulative, inherent toxicity as demonstrated by acute aquatic toxicity, and that the substance remains in commerce in Canada.
While there may be some conflicting evidence and significant uncertainties regarding the results, we are exercising a precautionary approach to propose that the substances meet the definition of toxic under s.64(a) and/or (b) of CEPA given the potential hazardous properties and potential risks posed by these high concern substances.
A specific example is the case of the Batch 1 dye chemical, CHPD. This substance was considered PBiT through categorization and, based on current information, remains in commerce in Canada. Much of the data considered in the screening assessment (physical and chemical properties, environmental fate, bioaccumulation, persistence and ecotoxicity data) was estimated through the use of models (e.g., quantitative structure-activity relationships, or QSAR). The weight of evidence indicates that this substance meets the P & B criteria and could harm aquatic organisms (iT). In addition, since accumulations of P and B substances may be widespread and are difficult to reverse, a conservative response to uncertainty was believed justified and, based on the above, the substance is being proposed to meet the definition of toxic under section 64(a).
Does the Advisory Panel support the approach taken for substances considered after assessment to be persistent, bioaccumulative, and inherently toxic?
Considerations:
Empirical data were sought, but little information was available (based on rapid search of most relevant information sources) or provided by industry. Industry and others have further opportunity to provide information during the up-coming public comment period.
For P & B & iT substances that are concluded to be toxic under section 64, the risk management objective is virtual elimination of releases.
Attachment:
Draft Screening Assessment Report for CHPD dye (CAS RN 54079-53-7)
Panel Response to Question 3:
"The Panel supports the recommended approach noting it as highly, but appropriately precautionary. The Panel notes that screening assessments based largely on modelling imply comparatively high levels of uncertainty."
Question 4
During the Challenge, additional information may be uncovered (either by government evaluators or through industry submission) which can change the PBiT status of a substance and influence its CEPA-toxic conclusion.
A specific example is the case of the pigments in Batch 1, such as Pigment Red 187. This substance was initially considered PBiT as a result of categorization and, based on current information, is still in commerce in Canada. New experimental data received during the Challenge suggested that this pigment has a low potential to accumulate in the lipid tissues of organisms. The substance is thus no longer expected to meet the criteria for bioaccumulation set out in the Persistence and Bioaccumulation Regulations. In addition, new experimental data for a structurally-similar chemical, as well as new predictions of toxicity that take into account revised estimates of bioaccumulation potential, suggest that the substance is of low acute toxicity to aquatic organisms. A very conservative quantitative risk quotient was then calculated for relevant exposure scenarios. Risk quotients provide estimates of potential risk by comparing concentrations predicted to occur in the environment (using conservative or reasonable worst-case assumptions) to levels expected not to have effects on organisms. Based on these considerations, the substance is proposed not to meet the definition of toxic under CEPA (64a and b).
This applies to all three pigments in Batch 1.
Given that, for certain substances, new evidence negates the original conclusions that they met each of the P, B, and iT criteria, the "predisposition" for a toxic conclusion no longer applies to those substances. Does the Advisory Panel agree that an appropriate level of precaution was exercised in the approach (and example) described?
Attachment:
Draft Screening Assessment Report for Pigment Red 187 (CAS RN 59487-23-9)
Panel's Response to Question 4:
The Panel removed the reference to the example in the question and solely addressed the approach.
"The Panel does support the approach articulated in Question 4."
Meeting Adjourned
Health Canada (1994) Human Health Risk Assessment for Priority Substances. Environmental Health directorate, Health Canada. Cat. No. En40-215/41E.
