Substituted Diphenylamines (SDPAs) - information sheet

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About these substances

  • Fourteen substituted diphenylamines (SDPAs) with similar chemical structures and physical-chemical properties were assessed as part of the Substance Groupings Initiative of the Chemicals Management Plan (CMP).
  • One of these substances is benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene, also known as BNST (CAS RN 68921-45-9).
  • BNST was previously assessed in 2009 as part of the Challenge Initiative. At that time, BNST was concluded as entering the environment at levels that may constitute a danger to the environment. However, based on new information obtained since its original assessment, BNST was re-assessed in this assessment of SDPAs.
  • The 14 SDPAs are industrial chemicals that do not occur naturally in the environment.
  • In Canada, SDPAs are mainly used as antioxidants in automotive and industrial lubricants, but also have some use in the manufacture of plastics or polyurethane foams and rubber products. SDPAs may be used as alternatives for each other.

Exposure of Canadians and the environment

  • Exposure of Canadians to SDPAs from the environment (for example, air, water, sediment or soil) is expected to be low.
  • Exposure of Canadians to SDPAs from the use of products available to consumers, such as foam cushioning and automotive lubricants, is expected to be low.
  • In Canada, SDPA manufacturing is expected to be the predominant sector leading to the release of these substances to the aquatic environment.
  • SDPAs also have the potential to be released to the environment during industrial activities (for example, blending lubricants, manufacturing plastic and rubber products) or during the use of lubricants.

Key health and ecological effects (hazard)

  • Some SDPA substances are associated with adverse health effects to the liver and blood. These effects were considered the "critical" or important effects for characterizing risk to human health in this assessment.
  • The potential for adverse effects from SDPAs in the environment is low. However, these substances are persistent, and certain SDPAs that have a higher potential to be taken up by organisms have a higher relative ecological hazard potential.

Risk assessment outcomes

  • The Government of Canada conducted a science-based evaluation of the substances in the SDPA grouping called a screening assessment, to address the potential for harm to Canadians and to the environment.
  • Under the Canadian Environmental Protection Act, 1999 (CEPA 1999), the risk posed by a substance is determined by considering both its hazardous properties (its potential to cause adverse human health or ecological effects) and the amount of exposure there is to people or to the environment. A substance may have hazardous properties; however, the risk to human health or to the environment may be low depending on the level of exposure.
  • Results of the final screening assessment indicate that the environmental concentrations of SDPAs are below the level expected to cause harm to organisms.
  • Based upon a comparison of levels to which Canadians can be exposed and the levels associated with health effects, it was determined that the risk to human health from the 14 SDPAs is low.
  • The Government of Canada published the Final Screening Assessment for Substituted Diphenylamines on December 9, 2017.

Screening assessment conclusions

  • As a result of this screening assessment, the Government concluded that the 14 SDPAs, including BNST, are not entering the environment at levels that are harmful to the environment.
  • The Government also concluded that these substances are not harmful to human health at current levels of exposure.

Preventive actions and reducing risk

  • Given the change in conclusion for BNST, the Government is proposing to delete BNST from Schedule 1 of CEPA 1999, also called the List of Toxic Substances.
  • The Prohibition of Certain Toxic Substances Regulations, 2012, were also amended to remove the restrictions on BNST.
  • Although the 14 SDPAs are not considered to be harmful to human health or the environment at current levels of exposure, some of the substances contain chemical structures that are available for uptake in organisms. Therefore, there may be a concern for the environment if exposures were to increase. Follow-up activities for the 9 substances identified by CAS RNs 4175-37-5, 10081-67-1, 27177-41-9, 36878-20-3, 68411-46-1, 68442-68-2, 68608-79-7, 68921-45-9, and 184378-08-3 will involve including the substances in future information gathering initiatives, such as a mandatory survey under section 71 of CEPA 1999.
  • The Government will use the data gathered through these follow-up activities to prioritize further information gathering or risk assessment of these substances, if required.

Important to know

  • Some SDPAs may be found in certain products available to consumers. Canadians should follow any safety warnings and directions on product labels and dispose of products responsibly. Products, including used oils, can be returned through the appropriate Product Stewardship Program in their jurisdiction.
  • Canadians who may be exposed to SDPAs in the workplace should consult with their employer and an occupational health and safety (OHS) representative about safe handling practices, applicable laws and requirements under the OHS legislation and the Workplace Hazardous Materials Information System (WHMIS).
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