Certain Benzidine-based dyes and related substances of the Aromatic Azo and Benzidine-based substance grouping

What are they?

  • Forty-two substances, including nine benzidine-based acid dyes, twenty-four benzidine-based direct dyes, two benzidine-based cationic indicators, two benzidine-based precursors, and five benzidine derivatives are included in this subgroup.
  • Benzidine-based dyes and related substances are man-made chemicals. They are not expected to occur naturally in the environment.

How are they used?

  • Historically, the benzidine-based dyes were primarily used in textiles and leather; however, most of these have been phased out of use internationally.
  • One direct dye, Direct Blue 14, is currently used in Canada in solutions for eye surgery.
  • The majority of the related substances are mainly used to prepare colouring agents and chemicals that become a part of other materials.
  • Based on the most recent data, none of these substances are manufactured in Canada nor imported into Canada.

Why is the Government of Canada assessing them?

  • These 42 benzidine-based dyes and related substances were identified as priorities for assessment based on categorization criteria of the Domestic Substances List, and/or were considered as priority substances based on other human health concerns.
  • Therefore, these 42 benzidine-based dyes and related substances were considered in the Substance Groupings Initiative. These substances were included for the screening assessment of potential risks to the environment and to human health.

How are Canadians exposed to them?

  • Exposure of the general population of Canada to the 42 benzidine-based dyes and other substances via environmental media is not expected.
  • Canadians may be exposed to Acid Red 97 and 3,3'-DMB during the use of certain consumer products, such as textiles, leather products, and cooking utensils.

How are they released into the environment?

  • Given limited commercial activity, releases to the environment are expected to be low.

What are the results of the assessment?

  • The Government of Canada has conducted a science-based evaluation of these 42 benzidine-based dyes and related substances, called a screening assessment.
  • Screening assessments address the potential for harm to the general population of Canada and the environment.
  • Hazards related to chemicals used in the workplace should be classified accordingly under the Workplace Hazardous Materials Information System (WHMIS).
  • Results of the screening assessment indicate that these substances may remain in the environment for a long time. The assessment found that all of these benzidine-based dyes and related substances are not expected to accumulate in organisms.
  • Furthermore, the quantity of these substances that may be released to the environment is below the level expected to cause harm to organisms.
  • The Government of Canada has therefore concluded that these benzidine-based dyes and related substances are not entering the environment at levels that constitute a danger to the environment.
  • The Government of Canada has also concluded that these 42 benzidine-based dyes and related substances are not harmful to human health at current levels of exposure.
  • However, given that some of these substances have health effects of concern, there may be concerns if exposures were to increase in Canada.

What is the Government of Canada doing?

  • Based on the conclusion of the final screening assessment, the Government of Canada proposes that no further action be taken on any of the 42 benzidine-based dyes and related substances.
  • Given the health concerns for some of these substances, the Government will investigate options on how best to monitor changes in the use profile of these substances. Stakeholders will have the opportunity to provide feedback on a consultation document, describing potential options for information gathering or preventative actions, to be published once assessment for all of the Aromatic Azo and Benzidine-based Substance Grouping are completed.
  • The Final Screening Assessment on Certain Benzidine-based Dyes and Related Substances was published on November 29, 2014.

What can Canadians do?

  • The health risks associated with a chemical depend on the hazard (its potential to cause health effects) and the dose (the amount of chemical to which you are exposed). The 42 benzidine-based dyes and related substances are not a concern for the environment or human health at current levels of exposure.
  • As a general precaution, Canadians are reminded when using any product to carefully follow any safety warnings and directions and to dispose of the products appropriately.
  • Canadians who may be exposed to these 42 benzidine-based dyes and related substances in the workplace should consult with their employer and occupational health and safety representative about safe handling practices, applicable laws and requirements under the Workplace Hazardous Materials Information System (WHMIS).
Benzidine-based Acid Dyes
CAS RN DSL name Colour Index name or acronym
6459-94-5 1,3-Naphthalenedisulfonic acid, 8-[[3,3'-dimethyl-4'-[[4-[[(4-methylphenyl)sulfonyl]oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-7-hydroxy-, disodium salt Acid Red 114
6548-30-7 1,3-Naphthalenedisulfonic acid, 8-[[3,3'-dimethoxy-4'-[[4-[[(4-methylphenyl)sulfonyl]oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-7-hydroxy-, disodium salt Acid Red 128
68318-35-4 2,7-Naphthalenedisulfonic acid, 4-amino-3-[[4'-[(2,4-dihydroxyphenyl)azo]-3,3'-dimethyl[1,1'-biphenyl]-4-yl]azo]-5-hydroxy-6-[(4-sulfophenyl)azo]-, trisodium salt Acid Black 209
68400-36-2 2,7-Naphthalenedisulfonic acid, 4-amino-5-hydroxy-6-[[4'-[(4-hydroxyphenyl)azo]-3,3'-dimethyl[1,1'-biphenyl]-4-yl]azo]-3-[(4-nitrophenyl)azo]-, disodium salt NAAHD
83221-63-0 2,7-Naphthalenedisulfonic acid, 4-amino-3-[[4'-[(2,4-diaminophenyl)azo]-2,2'-disulfo[1,1'-biphenyl]-4-yl]azo]-5-hydroxy-6-(phenylazo)-, sodium salt NAADD
3701-40-4 2,7-Naphthalenedisulfonic acid, 4-hydroxy-3-[[4'-[(2-hydroxy-1-naphthalenyl)azo]-2,2'-dimethyl[1,1'-biphenyl]-4-yl]azo] () Acid Red 99
10169-02-5 [1,1'-Biphenyl]-2,2'-disulfonic acid, 4,4'-bis[(2-hydroxy-1-naphthalenyl)azo]-, disodium salt Acid Red 97
6470-20-8 [1,1'-Biphenyl]-2,2'-disulfonic acid, 4-[(4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo]-4'-[(2-hydroxy-1-naphthalenyl)azo]-, disodium salt Acid Orange 56
89923-60-4 Benzenesulfonic acid, 3,3'-[(2,2'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis[azo(4,5-dihydro-3-methyl-5-oxo-1H-pyrazole-4,1- BADB
Benzidine-based Direct Dyes
CAS RN DSL name Colour Index name or acronym
72-57-1 2,7-Naphthalenedisulfonic acid, 3,3'-[(3,3'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[5-amino-4-hydroxy-, tetrasodium salt Direct Blue 14
6420-22-0 2,7-Naphthalenedisulfonic acid, 5-amino-3-[[4'-[(6-amino-1-hydroxy-3-sulfo-2-naphthalenyl)azo]-3,3'-dimethyl[1,1'-biphenyl]-4-yl]azo]-4-hydroxy-, trisodium salt Direct Blue 295
2429-74-5 2,7-Naphthalenedisulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[5-amino-4-hydroxy-, tetrasodium salt Direct Blue 15
71550-22-6 2,7-Naphthalenedisulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[5-amino-4-hydroxy-, tetralithium salt NADB·2Li
75659-72-2 2,7-Naphthalenedisulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[5-amino-4-hydroxy-, monolithium trisodium salt NADB·Li·3Na
75659-73-3 2,7-Naphthalenedisulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[5-amino-4-hydroxy-, dilithium disodium salt NADB·2Li·2Na
75752-17-9 2,7-Naphthalenedisulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[5-amino-4-hydroxy-, trilithium monosodium salt NADB·3Li·Na
573-58-0 1-Naphthalenesulfonic acid, 3,3'-[[1,1'-biphenyl]-4,4'-diylbis(azo)]bis[4-amino-, disodium salt Direct Red 28
992-59-6 1-Naphthalenesulfonic acid, 3,3'-[(3,3'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[4-amino-, disodium salt Direct Red 2
2150-54-1 2,7-Naphthalenedisulfonic acid, 3,3'-[(3,3'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[4,5-dihydroxy-, tetrasodium salt Direct Blue 25
2429-71-2 1-Naphthalenesulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[4-hydroxy-, disodium salt Direct Blue 8
6420-06-0 1-Naphthalenesulfonic acid, 4-hydroxy-3-[[4'-[(1-hydroxy-5-sulfo-2-naphthalenyl)azo]-3,3'-dimethyl[1,1'-biphenyl]-4-yl]azo]-, disodium salt Direct Violet 28
6449-35-0 1-Naphthalenesulfonic acid, 3-[[4'-[(6-amino-1-hydroxy-3-sulfo-2-naphthalenyl)azo]-3,3'-dimethoxy[1,1'-biphenyl]-4-yl]azo]-4-hydroxy-, disodium salt Direct Blue 151
75673-34-6 1-Naphthalenesulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[4-hydroxy-, dilithium salt NADB·2Li
75673-35-7 1-Naphthalenesulfonic acid, 3,3'-[(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[4-hydroxy-, monolithium monosodium salt NADB·Li·Na
6548-29-4 2,7-Naphthalenedisulfonic acid, 4,4'-[(3,3'-dichloro[1,1'-biphenyl]-4,4'-diyl)bis(azo)]bis[3-amino-, tetrasodium salt Direct Red 46
6655-95-4 Acetic acid, 2,2'-[[4,4'-bis[[1-hydroxy-6-[(4-methoxyphenyl)amino]-3-sulfo-2-naphthalenyl]azo][1,1'-biphenyl]-3,3'-diyl]bis(oxy)]bis-, tetrasodium salt Direct Blue 158
16071-86-6 Cuprate(2-), [5-[[4'-[[2,6-dihydroxy-3-[(2-hydroxy-5-sulfophenyl)azo]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-2-hydroxybenzoato(4-)]-, disodium Direct Brown 95
70210-28-5 Benzoic acid, 5-[[4'-[[6-amino-5-(1H-benzotriazol-5-ylazo)-1-hydroxy-3-sulfo-2-naphthalenyl]azo]-3,3'-dimethoxy[1,1'-biphenyl]-4-yl]azo]-2-hydroxy-4-methyl-, disodium salt BABHS
71215-83-3 Benzoic acid, 5-[[4'-[(2-amino-8-hydroxy-6-sulfo-1-naphthalenyl)azo]-2,2'-dichloro[1,1'-biphenyl]-4-yl]azo]-2-hydroxy-, disodium salt BAHSD
72252-59-6 [1,1'-Biphenyl]-3,3'-dicarboxylic acid, 4-[[5-[[5-(aminosulfonyl)-2-hydroxyphenyl]azo]-1-hydroxy-6-(phenylamino)-3-sulfo-2-naphthalenyl]azo]-4'-[[1-[[(3-carboxy-4-hydroxyphenyl)amino]carbonyl]-2-oxopropyl]azo]-, tetrasodium salt BDAAH
75673-18-6 2,7-Naphthalenedisulfonic acid, 5-amino-4-hydroxy-3-[[4'-[(1-hydroxy-4-sulfo-2-naphthalenyl)azo]-3,3'-dimethoxy[1,1'-biphenyl]-4-yl]azo]-, monolithium disodium salt NAAH·Li·2Na
75673-19-7 2,7-Naphthalenedisulfonic acid, 5-amino-4-hydroxy-3-[[4'-[(1-hydroxy-4-sulfo-2-naphthalenyl)azo]-3,3'-dimethoxy[1,1'-biphenyl]-4-yl]azo]-, dilithium monosodium salt NAAH·2Li·Na
67923-89-1 2,7-Naphthalenedisulfonic acid, 5-amino-4-hydroxy-3-[[4'-[(1-hydroxy-4-sulfo-2-naphthalenyl)azo]-3,3'-dimethoxy[1,1'-biphenyl]-4-yl]azo]-, trilithium salt NAAH·3Li
Benzidine-based Cationic Indicators
CAS RN DSL name Colour Index name or acronym
1871-22-3 2H-Tetrazolium, 3,3'-(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis[2,5-diphenyl-, dichloride TDBD
298-83-9 2H-Tetrazolium, 3,3'-(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis[2-(4-nitrophenyl)-5-phenyl-, dichloride TDBPD
Benzidine-based Precursors
CAS RN DSL name Colour Index name or acronym
93940-21-7 1-Triazene-1-carbonitrile, 3,3'-(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis- TCDB
91-92-9 -Naphthalenecarboxamide, N,N'-(3,3'-dimethoxy[1,1'-biphenyl]-4,4'-diyl)bis[3-hydroxy- Naphthol AS-BR
Benzidine Derivatives
CAS RN DSL name Colour Index name or acronym
119-93-7 1,1'-Biphenyl]-4,4'-diamine, 3,3'-dimethyl- 3,3'-DMB
612-82-8 1,1'-Biphenyl]-4,4'-diamine, 3,3'-dimethyl-, dihydrochloride 3,3'-DMB 2HCl
119-90-4 1,1'-Biphenyl]-4,4'-diamine, 3,3'-dimethoxy- 3,3'-DMOB
91-97-4 1,1'-Biphenyl, 4,4'-diisocyanato-3,3'-dimethyl- () TODI
366-29-0 [1,1'-Biphenyl]-4,4'-diamine, N,N,N',N'-tetramethyl- 4N-TMB

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