Summary of public comments received on the science approach document for the biomonitoring-based approach 2 for substances that contain barium, molybdenum, silver, thallium, or inorganic tin

Official Title: Summary of Public Comments Received on the Science Approach Document for the Biomonitoring-based Approach 2 for Substances that contain Barium, Molybdenum, Silver, Thallium, or Inorganic Tin

Comments on the Science Approach Document (SciAD) for the Biomonitoring-based Approach 2 for Barium-containing Substances, Molybdenum-containing Substances, Silver-containing Substances, Thallium-containing Substances and Inorganic Tin-containing Substances to be addressed as part of the Chemicals Management Plan (CMP) were provided by Prevent Cancer Now and Chemical Sensitivities Manitoba.

A summary of comments and responses is provided below, organized by topic:

1. New information & data updates

Summarized Comment Summarized Response
Include biomonitoring data for children less than 6 years of age. This SciAD builds on studies that include biomonitoring data for children under 6 years of age, such as the Canadian Health Measure Survey (3 to 79 years old, cycle 2 onwards) and the Maternal - Infant Research on Environmental Chemicals (MIREC) Child development Plus (children under 5 years) a follow-up study to the MIREC Study.
Include some nanomaterials in human biomonitoring with emphasis on those nanomaterials that have toxic properties in the macroform.     This SciAD does not explicitly include nanomaterials and associated health effects. The Government of Canada’s Proposed Approach to Address Existing Nanomaterials will consider nanoscale forms of substances currently on the Domestic Substances List.
For future biomonitoring approach documents, the Government of Canada should include additional details on toxicokinetics, gaps in biomonitoring data, sample collection, the laboratory analytical methods, and future possible biomarkers. This SciAD provides a quantitative scientific approach for identifying substances of low concern based on exposure and critical health effects. The biomonitoring approach outlines the suitability of a biomarker based on toxicokinetic data, and all data are reviewed and undergo quality control and quality assurance procedures. The reference materials found at the end of the SciAD document can verify this.
The document is inaccurate regarding organotins. It suggests that they were not of concern but, in fact, organotins were previously assessed in 2009 with important risk management actions, including virtual elimination of some organotins. This SciAD focussed on two inorganic tin substances. Organotin compounds were not included because they were not identified as priorities under Phase 3 of the CMP.
Improve consistency when using terminology for external dose, exposure, and toxicokinetics. Noted.

2. Methodology

Summarized Comment Summarized Response
This biomonitoring approach is not appropriate for chemicals with endocrine effects or potential developmental effects. Application of this approach is appropriate for substances known to have endocrine or developmental effects when there is an adequate biomarker, and understanding of the substances toxicology and the biomonitoring guidance value considers critical health effects.
The Government of Canada relies on findings and practices from other jurisdictions instead of conducting rigorous scientific analysis on toxicokinetic details and explicitly justifying the use of biomonitoring data. This may lead to misinterpretation of health risk. CMP approaches and assessments consider relevant, high-quality data from other jurisdictions with similar lifestyles, geography, or climate (such as the United States and European countries). These internationally conducted assessments also undergo rigorous review (including peer-review). The Government of Canada considers such assessments reliable, and in some cases contributes to the initial evaluation or review process. In all cases, a careful review of available data informs decisions when selecting the most appropriate biomonitoring approach. Information on different the types of approaches and assessments is available in the Chemicals Management Plan Risk Assessment toolbox.
The use of biomonitoring data in screening assessments is worthwhile, but its application must be defined and justified. Guidelines should be proposed, with public comment before final publication. This SciAD presents one method for applying biomonitoring data within CMP screening assessments and published for a 60-day public comment period. Guideline development is outside the scope of CMP assessments; however, the screening assessment that applies to this approach will be published for a public comment period.
Ensure that sufficient toxicokinetic data exist before considering biomonitoring as a strong basis for identifying chemicals that are of low concern. However, sufficient toxicokinetic data may not always exist. This biomonitoring approach is not appropriate for chemicals that tend to accumulate, that are rapidly metabolized, or that produce metabolites of concern. Available toxicokinetic data was carefully reviewed to develop the Science Approach Document (SciAD) for the Biomonitoring-based Approach 2. This SciAD is only recommended for substances that can be measured in the general population with suitable biomarkers of exposure, such as quantifying chemical concentration in whole blood, plasma, serum, or urine. The tendency of a substance to accumulate in tissues or to be rapidly metabolized does not prevent the use of biomarkers for risk characterization.
There are advantages in using biomonitoring data to assess risk, including: less dependence on modelled exposure data, cost effective, can be used to track efficacy of risk management, can be used to identify populations with higher chemical exposures, cultural differences, socio-economic influences, vulnerable populations, differences in individual exposures, exposures across a population, and link with health outcomes. Noted.

3. Risk characterization

Summarized Comment Summarized Response
The Government of Canada should consider the use of accurate biomonitoring data in environmental health impact assessments (EHIAs) targeting low-level, chronic chemical exposures of individuals, rather than the single chemical/health impact scenario. This SciAD is meant to assess substances under the CMP, which falls under CEPA. At this time, it is not intended to be used in EHIAs.
There are limitations when using biomonitoring data to assess risk. Limitations include difficulty of source attribution, biomonitoring data only specific to that time and array of circumstances, difficulty to detect trends in exposure, lack of sufficient toxicokinetic data, and difficulty in communicating risk to the public. The Government of Canada agrees that it is difficult to determine key sources of exposure with biomonitoring data alone. Therefore, information on exposure sources and their limitations was included in this SciAD. Some of these limitations are not unique to biomonitoring data and apply to all types of exposure data, including information that is specific to a time and array of circumstances, detection trends, and risk communication.
The Government of Canada could consider targeting regions with chronic low-level pollution or areas of high pollution, in addition to vulnerable populations. SciADs are based on the best available data. Targeted biomonitoring data will be included when available. For example, this SciAD included biomonitoring data from the State of the Science Report for Lead.
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