Acetic anhydride – information sheet

Acetic acid, anhydride
CAS Registry Number 108-24-7

On this page


  • The Government conducted a science-based evaluation of acetic acid, anhydride (acetic anhydride), 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 the environment. A substance may have hazardous properties; however, the risk to human health or to the environment may be low depending upon the level of exposure.
  • Using the Ecological Risk Classification of Organic Substances Approach, the substance was classified as having a low ecological hazard potential. More information on the hazard classifications can be found in that approach document.
  • Overall, exposure of the general population to acetic anhydride is expected to be negligible and there is a low risk of harm. Therefore, it is concluded that this substance is not harmful to human health or the environment.

About this substance

  • This screening assessment focuses on acetic anhydride.
  • It is considered a priority assessed as part of the third phase of the Chemicals Management Plan (CMP).
  • Acetic anhydride is an industrial chemical and does not occur naturally in the environment.
  • In Canada, it is used in the preparation of other chemicals and as a plasticizer in commercial building or construction materials, such as certain silicone sealants.
  • Acetic anhydride is a permitted food additive that is used to modify starches, which are food ingredients, and as a non-medicinal ingredient in pharmaceuticals.
  • Industry data collected by the Government indicates that acetic anhydride is not manufactured in Canada in quantities above the reporting threshold; however, it is reported to be imported into Canada.     

Exposure of Canadians and the environment

  • Canadians are not expected to be exposed to acetic anhydride via environmental media because of its rapid hydrolysis. In other words, the substance breaks down quickly with water.
  • Dietary exposure, if any, from consuming modified food starches used as food ingredients is expected to be negligible.
  • Use of acetic anhydride as a non-medicinal ingredient in prescription drugs or as a residual in certain silicone sealants is not expected to be a significant source of exposure to the general population.

Key health and ecological effects (hazard)

  • To identify effects of concern for human health, international reports of data on acetic anhydride were reviewed.
  • The Organisation for Economic Co-operation and Development (OECD) did not identify any concerns for carcinogenicity (cancer-causing ability), genotoxicity (adversely effects genetic material), developmental or reproductive toxicity.

Risk assessment outcomes

  • The OECD’s Cooperative Chemicals Assessment Programme developed a Screening Information Data Set (SIDS) and a SIDS Initial Assessment Report (SIAR) for acetic anhydride. The SIDSs and SIARs informed the evaluation of the substance. These assessments undergo rigorous review (including peer-review) and endorsement by international governmental authorities. Health Canada and Environment and Climate Change Canada are active participants in these processes, and the departments consider these assessments reliable.
  • The ecological risks of the substance were characterized using the Ecological Risk Classification of Organic Substances Approach. It identified acetic anhydride as having a low potential to cause ecological harm.
  • Considering the information presented, the risk to human health from acetic anhydride is low and there is a low risk of harm to organisms and the broader integrity of the environment.
  • The Government published the Final Screening Assessment for Acetic Anhydride on November 11, 2017.

Screening assessment conclusions

  • The Government concluded that acetic anhydride is not entering the environment at levels that are harmful to the environment.
  • The Government also concluded that the substance is not harmful to human health at current levels of exposure.

Important to know

  • Acetic anhydride is found in certain products available to consumers. Canadians should follow any safety warnings and directions on product labels and dispose of products responsibly.
  • Canadians who may be exposed to acetic anhydride in the workplace can consult with their employer and an occupational health and safety (OHS) representative about safe handling practices, applicable laws and requirements under OHS legislation and the Workplace Hazardous Materials Information System (WHMIS).

Page details

Date modified: