Consultation document on Octamethylcyclotetrasiloxane(D4): chapter 2

2. Background

2.1 Final Screening Assessment Report

A notice summarizing the scientific considerations of the final screening assessment report for D4 was published by Environment Canada and Health Canada in the Canada Gazette, Part I, on January 31, 2009, under subsection 77(6) of CEPA 1999. The approach taken in this ecological screening assessment was to examine available scientific information and develop conclusions based on a weight-of-evidence approach and using a precautionary approach, as required under section 76.1 of CEPA 1999.

The final screening assessment report (EC & HC 2008) concluded that D4 is entering or may be entering the environment in a quantity or a concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity, but is not entering the environment in a quantity or a concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.  Therefore, it was concluded that D4 met the criteria in paragraph 64 (a) of CEPA 1999.

The report also determined that the Predicted No-Effect Concentration (PNEC) for D4 is 0.0002 mg/L for the aquatic environment.

2.2 Proposed Risk Management Approach

The proposed Risk Management Approach for D4 was made public in January 2009 (EC & HC 2009). It identified potential risk management actions to achieve the lowest level of release of D4 to water that is technically and economically feasible.  

In order to address the environmental risks associated with D4, two regulations were proposed:

• to limit the quantity or concentration of D4 in certain personal care products and, where appropriate, in other consumer products that are manufactured in and imported into Canada; and
• to establish a maximum concentration of D4 in industrial effluents and require the implementation of a management system to ensure environmentally sound management practices are adopted at facilities where D4 is manufactured, transformed, or reformulated.

Based on analysis of D4 data related to consumer products received under the Challenge, it was determined that consumer use of cosmetics and toiletries has the most significant impact on the aquatic environment and there was no evidence of releases of D4 to water resulting from the use of other consumer products. For this reason, the Risk Management Approach for Products was modified to focus on concentration limits in certain personal care products.

The proposed requirements of both regulations are discussed further in Section 5 of this document. 

2.3  Environmental Monitoring

As part of the Chemical Management Plan Monitoring, Surveillance and Research Program, work is ongoing to collect information on levels of D4 in the following media: wastewater effluent and influent; surface water; sediment; fish; soils following sludge application and air. The data collected will provide information on levels of D4 in the ambient environment as well as an indication of the fate of D4 in wastewater systems.  As they become available, the results from this work will be used to inform the development of risk management measures and to later evaluate the performance of these measures.