Summary of public comments received on the draft screening assessment for the Siloxanes Group

Comments on the Draft Screening Assessment for the Siloxanes Group, assessed under the Chemicals Management Plan (CMP), were submitted by the Canadian Network for Human Health and the Environment, Dow Canada, Environmental Defence Canada, and the Silicones Environmental, Health, and Safety Center.

Summarized public comments and responses are provided below, organized by topic:

Methodology

Comment summary 1: The Government of Canada should consider evaluating the ecological risk classification of organic substances (ERC) approach against previously completed risk assessments in Canada that did not use ERC to assess the need for ongoing risk management activities for substances deemed toxic under the Canadian Environmental Protection Act, 1999 (CEPA). We encourage Canada to continue to refine its approach to chemicals management and believe that further opportunities are available for strengthening the exposure profiles that are developed using the ERC approach, including use of empirical data.

Response 1: The ecological risk classification of organic substances (ERC) approach was used to assist the government in identifying and addressing substances that may be of low concern to the environment, often based on lower volume or hazard rankings, in a more efficient manner and to identify substances of relatively higher concern that require more detailed risk evaluation.

Various types of information, both modelled and empirical, are incorporated into the prioritization and risk assessment process. Substances that have been identified as a potential concern based on the simplified approaches under ERC generally undergo a more detailed assessment, at which point empirical data, if available, can be considered in greater detail.

This approach is not intended to replace a more detailed assessment when one is merited, or to address the need for risk management of previously assessed substances. Performance measurement evaluations provide Canadians with information on the effectiveness of risk management actions in place for substances found to be toxic under the Canadian Environmental Protection Act, 1999 (CEPA 1999). For more information, please refer to performance measurement for toxic substances.

 

Comment summary 2: Since there are gaps in the Siloxanes database, the precautionary principle should have been applied in this assessment; there is concern that it was not.

Response 2: Precaution is applied in assessments conducted under CEPA, most notably in the use of protective approaches or assumptions when there is uncertainty. For more information, please refer to the Application of weight of evidence and precaution in risk assessment.

For example, for human health, the most susceptible subpopulation (for example, teens) as well as protective critical doses and effects are identified in the risk characterization, and conservative assumptions are used in the characterization of exposure.

In addition, the ecological risk classification of organic substances (ERC) approach uses a weight-of-evidence approach based on multiple lines of evidence to help minimize the potential for both over- and under-classification of hazard and exposure, and of subsequent risk classifications.

 

Comment summary 3: There is concern that there is no mention in the assessment of informed substitution.

Response 3: Given that the substances in the Siloxanes Group are not identified to be of concern to human health or the environment, no restrictions are proposed. As they will remain available for use, no pressing need to identify substitutes is expected. Should alternatives to substances in the Siloxanes Group be developed, new siloxanes would be subject to requirements under the New Substances Notification Regulations (Chemicals and Polymers), which allow for them to be assessed and any identified risks managed, before they enter the market in Canada.

 

Comment summary 4: There is concern that the Threshold of Toxicological Concern (TTC) approach is a criticized and  industry-favoured method. Recommendations about the TTC should be considered.

Response 4: The TTC approach was not used in this assessment. However, the Science Approach Document for the Threshold of Toxicological Concern (TTC)-based Approach for Certain Substances underwent external peer review and a 60-day public comment period and is considered robust. The uncertainties in the approach are discussed in section 5.0 of the above-mentioned document.

Transparency, conclusions, information, and data

Comment summary 5: There are concerns regarding recognition of subpopulations (potentially related to gender, age, occupation, or other vulnerabilities).

Specifically:

• Children’s routes of exposure to substances in the Siloxanes Group, including inhalation, dust ingestion and dermal absorption from products, should be accounted for in the assessment
• Occupational hazards and exposures need to be considered in the assessment, including consideration of gender and vulnerable groups

Attention should be given to the consequences of the predominant usage of siloxane-containing personal care products by women, and the vulnerability of younger women and girls to endocrine disruption.

Response 5:

Assessments conducted under CEPA are based on consideration of the best available information. An updated literature search (up to January 2022) was conducted during the development of the final assessment. References submitted as part of public comments were reviewed and considered with the other references obtained during the updated literature search.

When information is available that suggests a specific subpopulation or sex/gender may be at a greater risk than the general population (for example, due to increased biological susceptibility and/or increased exposure), conservative exposure scenarios that account for both the general population and the subpopulation of potential greater risk are considered in the risk assessment. Exposures are routinely estimated by age to take into consideration physical and behavioural differences during different stages of life. In this exposure assessment, exposures to Siloxanes from environmental media (including dust), food, and drinking water, and exposures to L2 and D3 from products available to consumers, were estimated for all relevant age groups, including teens, children, toddlers, infants, and people of reproductive age, when applicable. The highest exposure estimates were presented in the screening assessment and used in the health risk characterization to be protective of subpopulations of greater risk. A fact sheet on the consideration of vulnerable populations in risk assessment is available.

Regarding endocrine disrupting potential, available studies did not indicate that L2 or L4 are estrogenic. When determining the critical effects for human health risk characterization, exposure to Siloxanes from personal care products in different age groups of females including younger women and girls were considered to be protective of any female developmental and reproductive effects. A fact sheet on the consideration of endocrine-related effects in risk assessment is available.

The assessment focused on potential risks from exposure of the general population of Canada. Hazards related to chemicals used in the workplace are defined within the Workplace Hazardous Materials Information System (WHMIS).The Government of Canada is working with the provinces and territories to explore ways to enhance the protection of workers from exposure to chemicals by integrating and leveraging the information, tools, and/or technical expertise of the Chemicals Management Plan and Health Canada’s Workplace Hazardous Products Program.

 

Comment summary 6: Risk-based assessments under CEPA are being used to influence regulatory decision-making outside of Canada.

Response 6: Noted.

 

Comment summary 7: The decision to conclude that these chemicals do not meet the criteria set out in section 64 of CEPA is inconsistent with independent research and decisions made by authoritative bodies elsewhere. The Government should be consistent with the most protective actions taken by other governments and authoritative bodies.

Response 7: The assessment conclusion that the substances in the Siloxanes Group do not meet any of the criteria set out in section 64 of CEPA is consistent with other authoritative bodies.

Substances in the Siloxanes Group have been reviewed internationally through the Organisation for Economic Co-operation and Development (OECD) Cooperative Chemicals Assessment Programme (OECD 2009, 2013, 2014), Australia’s National Industrial Chemicals Notification and Assessment Scheme (AGDH) (2018, 2019), and the Danish Environmental Protection Agency (EPA) (2014). While OECD reviews the health effects of substances, assessments under the CMP also consider exposures to these substances to characterize risk to human health. Studies in the Danish EPA and OECD assessments informed the health effects characterizations in this assessment, and the reviews by AGDH are consistent with the assessment conclusion that the substances in the Siloxanes Group do not pose a concern to human health.

Additional data provided by the stakeholder are consistent with the findings of the ecological assessment.

 

Comment summary 8: There is a need for transparent, public and detailed responses to comments the Government receives about its assessments.

Response 8: The Government of Canada is committed to maintaining open and transparent assessment processes. As indicated in the assessment, the assessment has undergone a third-party science review and was published as a draft with a 60-day public consultation period before it was finalized. Health Canada and Environment and Climate Change Canada carefully reviewed all of the comments and information received, and changes were made to the risk assessment during its finalization, as appropriate. Additional information on the CMP assessment process can be found in the public comment process on Risk Assessment documents.

While all comments are taken into consideration, the final content and conclusion of assessments remain the responsibility of Health Canada and Environment and Climate Change Canada.

Comments are organized by theme (for example, information gathering, exposure, consultation), summarized, and responses are prepared in clear, concise, and less technical language.

A summary of public comments and responses (that is, this document) is published simultaneously with the final assessment on the Environment and Climate Change Canada Web site.

 

Comment summary 9: Current literature is missing or inappropriately or inadequately considered in the assessment. It is recommended that the Government conduct a full review of relevant studies to ensure they have a more complete picture of the health and environmental consequences.

Specific concerns include:

• The Government makes many assumptions and selects data in the assessment without fully explaining the choices
• The Government should provide a written rationale regarding how the studies submitted during the public comment period were considered

The Government should review information provided about the application of weight of evidence.

Response 9: Assessments focus on information critical to determining whether substances meet the criteria as set out in section 64 of CEPA by examining scientific information and incorporating a weight of evidence approach and precaution. They do not provide exhaustive summaries of existing relevant data considered for the assessment.

Additional studies provided during the public comment period, as well as results of an updated literature search, were carefully reviewed and considered during the development of the final screening assessment. Based on this review, additional relevant references were included in the final screening assessment.

Conclusions from the assessment reflect a weight of evidence and a precautionary approach, which weighs various sources of information to identify critical values used in the assessment and considers the relative relevance, strengths, and uncertainties of various data. It evaluates multiple lines of evidence, including the hazardous properties of the substance and the nature and extent of the exposure of Canadians and the environment to the substance, to determine if a substance may pose a risk to human health or to the environment. For more information, please refer to the Application of weight of evidence and precaution in risk assessment.

When Canadian exposure data are not available, international data are reviewed, taking into consideration factors such as data quality and relevance to Canada. If international data are not considered relevant to Canada, modelled values are estimated based on measured or estimated substance-specific data. A conservative approach is used for the selection of data points in the human health portion of the assessment (for example, by selecting maximum or 95^th percentile concentrations for estimating exposure). 

The assessment notes data gaps related to the risk characterization for all substances in the third phase of CMP Siloxanes Group under Section 7.1 “Uncertainties in evaluation of risk to human health.”

 

Comment summary 10: The government should revise the Siloxanes assessment to address concerns related to cyclomethicone.

Specifically:

• Given cyclomethicone is a UVCB, the assessment fails to justify assumptions with regards to content of D4, D5 and D6 in cyclomethicone
• There is concern that the cyclomethicone data used to inform the previous assessments are out-of-date and no longer relevant
• The available literature has shown that D4, D5 and D6 can penetrate the skin’s stratum corneum; however, this is not reflected in the assessment
• The assessment does not explain whether there is a potential for cumulative, aggregate or synergistic effects associated with concurrent and continuous exposure to D4, D5 and D6 from cyclomethicone
• The cyclomethicone assessment stands in contrast to the toxicity conclusions, risk management measures and prohibitions adopted in the E.U. on D4, D5 and D6

Additional research papers or additional data on cyclomethicone or D4, D5, and D6 should be considered in the assessment.

Response 10: Based on the available information in the published literature, although the proportion of its components is variable, cyclomethicone is known to be composed primarily of D4, D5 and D6. The human health and ecological risk of cyclomethicone were addressed as part of the previous Health Canada and Environment and Climate Change Canada  assessment reports of D4, D5, and D6 and the revised conclusion regarding D5 (Environment Canada, Health Canada 2008a, 2008b, 2008c; Canada 2012a ) and no further risk assessment of cyclomethicone is considered necessary at this time. Previous assessments found D5 and D6 do not to pose a risk to the environment or human health, while D4 was concluded to pose a risk to the environment but not to human health.

Previous D4, D5 and D6 assessments address human health exposure to cyclomethicone including exposure from the use of personal care products and dermal exposure. During the risk characterization of D4, D5 and D6, conservative assumptions were made and it was determined that the margins of exposure were adequate to address uncertainties.

Therefore, no further risk assessment of cyclomethicone is being conducted at this time. The final assessment was updated accordingly and does not include a conclusion under Section 64 for cyclomethicone.

With regards to the ecological assessment of cyclomethicone, risk management in place for D4 will continue to apply to D4 in cyclomethicone.

The Government can review any new scientific evidence on D4, D5, D6 and cyclomethicone in use in Canada, through prioritization processes such as the Identification of Risk Assessment Priorities (IRAP) process, including potential changes in exposure as indicated by changes in reported volumes/uses. Environment and Climate Change Canada has monitored D4 for many years and continues monitoring D4 in wastewater and the environment and is in the process of assessing effectiveness of RM measures taken so far to see if additional risk management measures are required.

Physical and chemical properties

Comment summary 11: The Henry’s law constant and the logK_OC values in the assessment differ from those reported in the compound-specific SEHSC documents (SEHSC 2019a, 2019b).

Response 11: These values reported for D3 and dvTMDS have been included in the final assessment, and the relevant sources have been cited.

Sources and releases

Comment summary 12: D3 has been reported in air, wastewater, effluent, surface water, sediment, soil, sludge, and biota. The results from D3 monitoring programs should be viewed with caution. D3 can appear to be present in the environment when it was actually formed as an artifact of the analytical detection technique. There is similar concern regarding the detection of D3 in personal care products, especially since D3 is not known to be intentionally added.

Response 12: Noted. Potential exposures of D3 to Canadians from environmental media or use of products is assessed based on the available data. D3 concentrations in personal care products have been reviewed and updated in the final assessment, where needed, taking into consideration analytical detection techniques.

The “Uncertainties in evaluation of risk to human health” section of the assessment has been updated to reflect the uncertainty in D3 concentration in environmental media and personal care products due to its potential formation during certain analytical detection techniques.

 

Comment summary 13: Several studies found in the open literature support the conclusion that D4, D5, D6, L4 and L5 are persistent in the environment.

Response 13: In previous assessments under the Challenge Initiative, D5 and D6 were determined to meet the criteria for persistence in air, water, sediment and soil, while D4 met the criteria in air and sediment. Additionally, L4 and L5 met persistence criteria under categorization in 2006.

The substances in the Siloxanes Group were identified by ERC as having an overall low risk potential. Their persistence and bioaccumulation properties relative to regulatory criteria were therefore not further investigated. It is also noted that the paper cited by the stakeholder compares half-lives in media to European persistence criteria, which are different from those defined under the Persistence and Bioaccumulation Regulations.

References

[AGDH] Australian Government Department of Health. 2018. Human health Tier II assessment for decamethyltetrasiloxane: CAS Number 141-62-8. Sydney (AU): Department of Health, National Industrial Chemicals Notification and Assessment Scheme (NICNAS).

[AGDH] Australian Government Department of Health. 2019. Human health Tier II assessment for hexamethyldisiloxane: CAS Number 107-46-0. Sydney (AU): Department of Health, National Industrial Chemicals Notification and Assessment Scheme (NICNAS).

[Danish EPA] Danish Environmental Protection Agency. 2014. Siloxanes (D3, D4, D5, D6, HMDS) : Evaluation of health hazards and proposal of a health-based criterion for ambient air. Odense (DK): Danish EPA. 82 pp. Environmental Project No. 1531.

[OECD] Organisation for Economic Co-operation and Development. 2009. SIDS initial assessment report for: Hexamethylcyclotrisiloxane (D3); CAS RN 541-05-9. SIAM [SIDS Initial Assessment Meeting] 26; 2008 April; Paris, France. [accessed 2020 Apr 7].

[OECD] Organisation for Economic Co-operation and Development. 2013. SIDS initial assessment report for: Hexamethyldisiloxane; CAS RN 107-46-0. CoCAM [Cooperative Chemicals Assessment Meeting] 1; 2011 October; Paris, France. [accessed 2020 Apr 7].

[OECD] Organisation for Economic Co-operation and Development. 2014. SIDS initial assessment report for: 1,1,3,3-tetramethyl-1,3-divinyldisiloxane; CAS RN 2627-95-4. CoCAM [Cooperative Chemicals Assessment Meeting] 5; 2013 October; Washington, DC. [accessed 2020 Apr 7].