Benzenamine, N-phenyl-, Reaction Products with Styrene and 2,4,4-Trimethylpentene (BNST)

CAS Registry Number 68921-45-9

What is it?

  • Benzenamine, N-phenyl-, Reaction Products with Styrene and 2,4,4-Trimethylpentene, also known as BNST, is an industrial chemical. It is not expected to occur naturally in the environment.
  • BNST is part of the chemical category of Substituted Diphenylamines (SDPAs).

How is it used?

  • BNST is predominantly used as an antioxidant additive in automotive and industrial lubricants.
  • BNST is also used as an antioxidant and anti-degradant additive in the manufacture of rubber products.
  • BNST was added to the Prohibition of Certain Toxic Substances Regulations, 2012, in 2013. These Regulations prohibit the manufacture, use, sale, offer for sale, and import of BNST with exemptions for certain activities.
  • As a result, BNST may still be used as an additive in lubricants until March 2018 if a permit has been granted under these Regulations. The use of BNST as an additive in rubber is exempted; except in tires, where this use has been prohibited in Canada.

Why is the Government of Canada assessing it?

  • In 2006, BNST was identified as a potential concern to the environment based on available information regarding possible persistence, accumulation in organisms and potential to cause harm to organisms.
  • A Final Screening Assessment for BNST and a Proposed Risk Management Approach Document for BNST were published in August 2009. At that time, BNST was concluded as entering the environment at levels that may constitute a danger to the environment.
  • Based on new information and chemical similarity to other SDPAs, BNST is being re-assessed in a more recent SDPAs assessment as part of the Substance Groupings Initiative.

How are Canadians exposed to it?

  • Exposure of the general population to BNST through air, water and soil is expected to be low.
  • Canadians are expected to have minimal exposure to BNST through the use of products available to consumers (for example, automotive lubricants).

How is it released into the environment?

  • In Canada, BNST is predominantly released to the aquatic environment from chemical manufacturing activities.
  • Releases to the environment may also be expected from other industrial activities (for example, blending of lubricants, manufacturing rubber products) or during the use of lubricants.

What are the results of the SDPAs (including BNST) assessment?

  • The Government of Canada has conducted a science-based evaluation of BNST, together with the SDPAs grouping, called a screening assessment. This re-assessment of BNST is based on new information obtained since its original assessment in 2009.
  • Screening assessments address the potential for harm to the general population of Canada and the environment.
  • The draft screening assessment indicates that SDPAs have the potential to remain in the environment for a long time. However, the concentrations of SDPAs found in the environment are below the levels expected to cause harm to organisms.
  • The Government of Canada is therefore proposing that the fourteen SDPAs, including BNST, are not entering the environment at levels that constitute a danger to the environment. This proposed change in conclusion for BNST is based on new information obtained since its previous assessment in 2009.
  • The Government of Canada is also proposing that the fourteen SDPAs, including BNST, are not harmful to human health at current levels of exposure.

What is the Government of Canada doing?

What can Canadians do?

  • The health risks associated with a chemical depend on the hazard (its potential to cause health effects) and the amount of chemical to which a person is exposed.
  • BNST is not presently a concern for human health at current levels of exposure.
  • As a general precaution, Canadians are reminded, when using any product, to carefully follow safety warnings and directions and to dispose of the products appropriately.
  • Canadians can also help by returning products, including used oils, through the appropriate Product Stewardship Program in their jurisdictions.
  • Canadians who may be exposed to BNST in the workplace should consult with their employer and 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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