Consultation document on risk management measure for BNST: chapter 2

2 Background

2.1 Final Screening Assessment Report

A notice summarizing the scientific considerations of the final Screening Assessment Report⁴ was published by the Government of Canada in the Canada Gazette, Part I, on August 1, 2009. The approach taken in this screening assessment report 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 the Canadian Environmental Protection Act, 1999 (CEPA 1999).

BNST is a UVCB (Unknown or Variable Composition, Complex Reaction Products, or Biological Materials). BNST is a reaction product of diphenylamine substitution with a blend of styrene and isooctane (also known as di-isobutylene). The reaction product is a mixture of diphenylamines (the mixture differs by the type and extent of substitution of the phenyl group), the nature of which may be variable depending on the ratio of styrene to di-isobutylene used during the manufacture. As it is not a discrete chemical, BNST may be characterized by multiple structures in order to provide a range of properties of the mixture and thus the best possible characterization for assessment purposes. BNST was evaluated based on two structures that are representative of the UVCB.

The Final Screening Assessment Report concluded that BNST is entering or may be entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. Therefore, it is concluded that BNST meets the criteria set out in paragraph 64(a) of CEPA 1999. Additionally, BNST meets the criteria for persistence and bioaccumulation potential as set out in the Persistence and Bioaccumulation Regulations (Canada 2000)⁴ .

2.2 Proposed Risk Management Approach

A proposed Risk Management Approach for BNST² was also published on August 1, 2009. It identified potential risk management actions to address environmental risk associated with BNST.

The proposed environmental objective is virtual elimination (VE). It follows a proposed risk management objective to achieve the lowest level of release of BNST to the environment that is technically and economically feasible from all life-cycle stages.

In order to achieve the risk management objective and to work towards achieving the environmental objective, the addition of BNST to the Prohibition Regulationsis being considered. This Amendment to the Prohibition Regulations would prohibit the manufacture, use, sale, offer for sale and import of BNST and products or formulations containing BNST.²

2.3 Environmental Monitoring

Monitoring for BNST in the environment will be conducted under a comprehensive monitoring and surveillance strategy for substances of interest under the Chemicals Management Plan. As part of the Chemicals Management Plan monitoring, BNST will be monitored in municipal wastewater, sediment and biota. Monitoring will be used to inform the federal government on releases of BNST to the environment.²