Aromatic Azo and Benzidine-based Substance Grouping

The aromatic azo and benzidine-based substances are among those identified as priorities for action following the categorization process and based on additional human health concerns. Some of the substances within this substance grouping may break down to certain aromatic amines or benzidines due to the potential cleavage of the azo bonds within the molecules. Those substances have been identified by other jurisdictions as a concern due to potential release of aromatic amines or benzidines that are known or are likely to be carcinogenic. Some of the substances in this substance grouping are known to be or may be found in imported consumer products in Canada (for example, clothing, leather products, cosmetic and personal care products). As outlined in the notice of intent for the Aromatic Azo and Benzidine-based Substance Grouping, it was recognized that assessments and conclusions pertaining to some of the substances that were previously assessed under other initiatives may be subsequently updated as part of the subgroup assessment.

Information gathering

Section 71 Chemicals Management Plan 2023

In June 2023, a notice was published in the Canada Gazette, Part I: Vol. 157, No. 25 – June 24, 2023 under section 71 of the Canadian Environmental Protection Act, 1999 (CEPA 1999). This notice applies to 10 substances included in this substance grouping (CAS RNs 6253-10-7, 69472-19-1, 6250-23-3, 2832-40-8, 21811-64-3, 6300-37-4, 27184-69-6, 6657-00-7, 65122-05-6, and 842-07-9). More information is available on the Information gathering with respect to certain substances under the Chemicals Management Plan web page.

2011 Mandatory survey - section 71 notice

In December 2011, a notice was published in the Canada Gazette, Part I: Vol.145, No.51 - December 17, 2011 under section 71 of CEPA 1999. This notice applied to a subset of the aromatic azo and benzidine-based substances covered in this initiative.
The information collected from this section 71 notice informed the risk assessment and, if necessary, risk management for these substances. Information provided to Environment and Climate Change Canada and Health Canada under previous initiatives was also taken into consideration.

A compilation of the non-confidential data received on aromatic azo and benzidine-based substances in response to the section 71 notice, including information submitted on a voluntary basis, is available via the Government of Canada Open Data Portal. Along with the compilation, a non-confidential information summary provides general information on the volume of information received and the substances, activities, substance functions, commercial uses and sectors most often reported.

Consultation document

Some aromatic azo and benzidine-based substances, although concluded not to pose a risk to the environment or to human health at current levels of exposure, may be a concern if environmental exposures or exposures of the general population of Canada to these substances were to increase.

Options on how best to monitor changes in uses of substances identified to have environmental and/or human health effects of concern are being investigated, and this was communicated to stakeholders when the draft screening assessments were published. Health Canada and Environment and Climate Change Canada have published a Consultation Document on the Options for Addressing Aromatic Azo and Benzidine-based Substances with Effects of Concern, which describes potential options for information gathering or preventive actions on substances identified to have environmental or health effects of concern.

Stakeholders had the opportunity to contribute feedback during the consultation period, which ended May 10, 2017.


Draft screening assessments were published in 2013 and 2014. Each publication was followed by a 60-day public comment period. Final screening assessments were published between 2014 and 2017. Follow-up information gathering to inform risk management actions may be conducted following publication of the final screening assessments if it is determined to be required.

Publication timelines
Subgroup Publication of the final screening assessment
Certain aromatic amines May 28, 2016
Certain azo acid dyes June 18, 2016
Certain azo basic dyes May 28, 2016
Certain azo direct dyes and azo ractive dyes April 4, 2015
Certain azo disperse dyes March 11, 2017
Certain azo metal complexes and other azo substances April 4, 2015
Certain azo solvent dyes May 28, 2016
Certain benzidine-based dyes and r elated substances November 29, 2014
Certain diarilyde yellow pigments October 11, 2014
Certain monoazo pigments May 28, 2016

Historical information

Subgrouping approach

To address substances in this grouping, the Government of Canada developed a subgrouping approach for 358 aromatic azo and benzidine-based substances based on structural similarities, physical-chemical properties, common functional uses and applications. The subgrouping approach has undergone a series of consultations including external peer reviews and a multi-stakeholder technical consultation meeting held in March 2012 in Ottawa, Canada. A record of this meeting can be found in the Meeting summary report on multi-stakeholder consultation on the proposed subgrouping approach of the aromatic azo and benzidine based substances.

Under this subgrouping approach, the majority of the substances are first divided into two chemical categories based on the chemical structure of the substances: Chemical Category I: Aromatic azo-based substances and Chemical Category II: Benzidine-based substances.

Within each chemical category, substances are further divided based on their "application classes". Application classes of substances are related to their physical-chemical properties and potential commercial uses. Application classes identified for the substances in this substance grouping are: pigments, dyes (including solvent dyes, disperse dyes, acid dyes, direct dyes, reactive dyes, basic dyes, mordant dyes, and food dyes), precursors, indicators and aromatic amines. Substances within each subgroup may further be divided based on more detailed structural similarities. Limited scientific information is available for many of the substances in this grouping and identification of structurally related substances supports use of read-across approaches when conducting screening assessments.

Subgrouping approach background document

A draft subgrouping approach background document for the screening assessment of aromatic azo and benzidine-based substances was released in July 2012. This document outlined the subgrouping approach, summarized overarching technical knowledge on this substance grouping, and provided Canadian as well as international regulatory context. Comments received during the 60-day public comment period on this draft document centered on clarifying the purpose of the document, including more Canadian context, addressing pigments and dyes separately, and considerations for the proposed approaches for subgrouping and assessment of each subgroup. Comments have been considered in finalizing the approach document and in the context of drafting the screening assessments. The Final Subgrouping Approach and Background Information Document for the Screening Assessment of Aromatic Azo and Benzidine-based Substances is now available upon request. Please contact us to request a copy.

Notice of intent

In June 2010, the Government of Canada published a notice of intent to address Aromatic azo and benzidine-based substances in the Canada Gazette, Part I: Vol. 144, No. 23 - June 5, 2010.

The notice of intent indicated that the Government of Canada planned to assess the potential health and ecological risks of these substances. If, through the assessment process, it is determined that any of these substances are considered harmful to human health or the environment, then management action would be considered for those substances where appropriate.

Public comments on the notice of intent were received through the 60-day public comment period. The Government of Canada has considered the comments received and a summary of the main public comments received on the notice of intent and government response is available.

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