Summary of public comments received on the draft screening assessment and risk management scope for the decenes group
Comments on the Draft Screening Assessment and Risk Management Scope for the Decenes Group, assessed under the Chemicals Management Plan (CMP), were submitted by ExxonMobil Biomedical Sciences Inc., the Canadian Consumer and Specialty Products Association, the Canadian Fuels Association, and the American Chemistry Council Higher Olefins Panel.
Summarized public comments and responses are provided below, organized by topic.
Methodology
Comment Summary 1: Submitter notes that resources and assessment of available literature in the draft screening assessment were appropriate and included appropriate limitations.
Response 1: Noted.
Comment Summary 2: Given the screening nature of the assessment, the stakeholder would like Health Canada and Environment and Climate Change Canada to elaborate on what refinements are considered before risk management decisions are initiated.
Response 2: Assessments conducted under the Canadian Environmental Protection Act, 1999 (CEPA) are based on sound science, consider multiple lines of evidence and uncertainties, and apply precaution, where warranted.
Consultation with stakeholders is an essential part of the risk management process. The Government of Canada is committed to consulting extensively with all affected stakeholders when applying risk management measures. Stakeholders have the opportunity to provide feedback or inform the Government of their activities after the publication of the Risk Management Scope and Risk Management Approach documents.
Comment Summary 3: Submitter requests clarification on the acceptable margin of exposure (MOE) in the draft screening assessment and whether reversibility of the effect was considered.
Response 3: The reversibility of the effect was considered in the determination of the critical endpoint and additional text was added to the final assessment.
The acceptability of an MOE is determined by considering many factors such as the severity of health effects endpoints; the exposure regimen used in a critical animal study; the potential duration of human exposure; and the inherent hazard of the substance. The final assessment clarifies that an MOE of greater than 300 was considered adequate.
Comment Summary 4: Submitter inquired if a study quality assessment was done for the critical study used for the point of departure.
Response 4: Studies cited in the assessment were critically reviewed and evaluated for data quality. Only studies deemed to be of satisfactory reliability and acceptable quality were used in the assessment. In addition, external peer reviews are conducted prior to the publication of the draft assessment and are critical to ensuing the relevance and accuracy of data and information applied in the assessment.
Information and data
Comment Summary 5: The stakeholder flagged information previously submitted to Health Canada and Environment and Climate Change Canada.
Response 5: The information provided previously was considered and used in the draft and final assessment.
Environmental persistence
Comment Summary 6: It is unclear what the definition of persistence is in the context of the assessment. The definition of overall persistence (Pov) from the Ecological Risk Classification of Organic Substances (ERC) science approach document is incompatible with the single-media half-life criteria for persistence from the Persistence and Bioaccumulation Regulations of CEPA.
Response 6: The Decenes Group assessment used the ERC approach to evaluate the potential for risk to the Canadian environment from exposure to these chemicals. In ERC, various lines of evidence including Pov, which is a multimedia or whole environment persistence measure following release to water, are combined to identify substances as warranting further evaluation of their potential to cause harm to the environment or as having a low likelihood of causing harm to the environment. Pov is used in ERC as a descriptor to determine the potential for long-term exposure in the environment and it is not used for regulatory conclusions of persistence under the Persistence and Bioaccumulation Regulations of CEPA.
The Decenes Group draft screening assessment also considered single-media half-lives in its persistence section. These values were remodelled and revisions were made to the final assessment to clarify the context of persistence characterization, where appropriate.
Comment Summary 7: No clear justification is provided as to why hydrogenated trimer and tetramer of decene (HTTD) is expected to be persistent in water, sediment and soil. Available data indicates that HTTD is not persistent in the environment.
The exposure classification for HTTD should also be reconsidered.
Response 7: Upon additional persistence modelling of single-media half-lives and review of submitted data, it was determined that HTTD is not expected to persist in water, sediment and soil. Changes have been made to the final assessment accordingly.
Based on the information considered under the ERC approach, HTTD was classified as having a moderate exposure potential. This characterization took some aspects of environmental fate into consideration (for example, chemical half-lives in various media and biota, partition coefficients, and fish bioconcentration). The data used in the exposure classification were reviewed; however, no further changes were made to the exposure classification outcome.
Human exposure assessment
Comment Summary 8: Stakeholder wanted more information on whether human exposures were normalized (or adjusted) to match with the exposure duration of the toxicity study.
Response 8: Exposure was not normalized (or adjusted) to match the exposure duration of the critical toxicity study because the health effects were not dependent on the average dose but rather on the peak dose. The assessment has been updated to provide additional clarification.
Comment Summary 9: Stakeholder found the inhalation exposure modelling to be too conservative and suggested a refinement to the maximum concentration for the aerosol product as well as use of certain default parameters for the model in the assessment.
Response 9: Refinements and adjustments were made to the exposure parameters and incorporated into the final assessment.
Health effects
Comment Summary 10: Submitter inquired if adjustment of the point of departure for exposure duration was considered including use of a modified Haber’s Law to predict effect concentrations.
Response 10: Adjustment of the point of departure for duration was not considered in the Decenes Group assessment, as the observed effects were considered related to the concentration of hydrogenated didecene administered to rats rather than the total intake. The paper cited by the stakeholder on modified Haber’s Law evaluated information for volatile industrial chemicals. The Decenes Group substances are substances of unknown or variable composition, complex reaction products or biological materials (UVCBs) and have very low to moderate volatility, based on available information.
Comment Summary 11: Submitter requested clarification regarding selection of the single exposure 100 mg/m3 concentration as the lowest observed adverse effect concentration (LOAEC) in the inhalation assessment, and if reversibility was considered.
Response 11: As discussed in the draft screening assessment, the selection of the LOAEC of 100 mg/m3 was based on observed respiratory tract histopathology effects after exposure and incomplete recovery after 14 days in exposed rats.
Reversibility of the observed effect was considered in determining the point of departure.
The severity and incidence of observed effects after recovery in the key acute study were reconsidered. As such, the LOAEC of 100 mg/m3 was revised to a no-observed-adverse-effect concentration (NOAEC) in the final assessment.
Comment Summary 12: The submitter considers that HTTD does not share the hazard profile of hydrogenated didecene. The submitter suggested further discussion in the assessment of differences between these substances as well as read-across analogues.
Response 12: In the absence of appropriate acute inhalation studies on HTTD, the critical effect level for hydrogenated didecene is used in the assessment for risk characterization. Additional discussion on this consideration has been added to the final assessment.
Risk characterization
Comment Summary 13: The submitter requested additional considerations, such as assessment of study quality, reversibility of effect, and adjustment of the point of departure or exposures, be included in the uncertainties section.
Response 13: The additional considerations noted by the stakeholder were not included in the uncertainties section. However, clarifications were made throughout the final assessment, where appropriate, based on the input provided by the stakeholder.
Risk management
Comment Summary 14: The submitter requested confirmation that workplace products are not included in the Risk Management Scope. The submitter also mentioned that if additional information for workplace products is required, they will relay the request to their members.
Response 14: The proposed risk management measures are intended only for aerosol/spray products containing hydrogenated didecene and/or HTTD available to consumers.
Comment Summary 15: The submitter supports the proposed risk management measures, requests that stakeholders be notified if future risk management measures will be considered for exposure scenarios other than those outlined in the Risk Management Scope document. Additionally, the submitter is requesting that economic impacts be taken into consideration for any future risk management measures for products in formats other than the proposed aerosol/spray format.
Response 15: The Government of Canada will carefully consider and evaluate the need to risk manage scenarios other than those outlined in the Risk Management Scope document if deemed necessary. Should future risk management measures for products in formats other than the proposed spray/aerosol format be required, economic impacts will be taken into consideration and stakeholders will be notified accordingly.