Report of the Board of Review for Decamethylcyclopentasiloxane (Siloxane D5)

9 Observations and Recommendations

• 9.1 Persistence and Bioaccumulation Regulations
• 9.2 Availability and Transparency of the Models
• 9.3 Conduct of Screening Assessments

300. During the course of this review, the Board was made aware of several matters about which it would like to offer comments. These comments are intended only to offer guidance to government and industry officials with respect to the framework within, and the conduct of, risk assessments.

9.1 Persistence and Bioaccumulation Regulations

301. The Board encourages the Department(s) to regularly review, and update as appropriate, the Regulations. As evidenced by the new information that the Board was able to consider in this proceeding, advancements in sampling, measurement, and analysis provide new and refined techniques available to determine whether substances pose a danger to the environment (or human health). The Regulations should be reviewed periodically to ensure that they reflect current scientific standards and risk assessment methodologies.

302. The Board also is of the opinion that a guidance document should be issued by the Department(s) describing how parameters such as persistence, bioaccumulation, and intrinsic properties are examined in a risk assessment. Such a document should be developed in consultation with stakeholders and would provide a clear understanding of how the Department(s) interpret(s) the Regulations and would guide the conduct of science needed to address these requirements.

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9.2 Availability and Transparency of the Models

303. As discussed in section 4.2.1, models can be used to estimate releases to the environment, as well as their fate and distribution after release. Models can be of particular assistance when a chemical is being evaluated and there are limited empirical measurements of concentrations in the environment.

304. In the scientific community, it is generally accepted practice that models are fully specified and, to the extent possible, transparent. Consequently, the algorithms are fully described and the source code is accessible. Further, all input data provided to the model or tool and the output generated should generally be made available, subject to considerations respecting confidential information. When inputs to a model or tool do include confidential information, government officials should attempt to find ways that the model or tool and their inputs can be disclosed without revealing confidential information. In addition, the model or tool should be validated against measured data for the substance or for similar substances to those being tested.

305. The Board encourages Environment Canada to update its models or tools regularly and to seek the input of subject matter experts both within and outside the government to ensure the integrity of their models or tools and to ensure that both users and stakeholders are aware of the strengths and weaknesses of models or tools.

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9.3 Conduct of Screening Assessments

306. It was not within the Board’s mandate to pronounce on the process followed by government and industry in the Screening Assessment. However, the Board did have some observations:

• It is appropriate for government officials to adopt a conservative or precautionary approach to ensure the protection of the environment and human health in the absence of a comprehensive data set and analysis.
• The Board strongly encourages industry and interested stakeholders to work diligently with government officials when screening assessments are being conducted in order to fill data gaps and provide relevant commentary and analysis.

DATED this 20th day of October, 2011

John p. Giesy, Ph.D., FRSC
Chair, Siloxane D5 Board of Review

Keith R. Solomon, Ph.D., Fellow ATS
Member, Siloxane D5 Board of Review

Sam Kacew, Ph.D., Fellow ATS
Member, Siloxane D5 Board of Review