Formation of Carcinogenic Aromatic Amines from AZO Dyes

Formation of Carcinogenic Aromatic Amines from AZO Dyes

Md. Noor Hossain
B.Sc Engg.(Textile): BUTex, MBA: DU;
Merchandiser: Epyllion Group
Email: noor.butex@gmail.com



Introduction:
Azo dyes represent the major class of dyestuffs. Azo colorants are the most important class of synthetic dyes and pigments, representing 60 – 80% of all organic colorants. They are used widely in substrates such as textile fibres, leather, plastics, papers, hair, mineral oils, waxes, foodstuffs and cosmetics. Henceazo colorants are part of our everyday colorful life, they are all around us and we could not do without them because It allows colors with outstanding colorfastness and wide range of spectrum of colors.

Some of these AZO dyes have the capacity to release certain aromatic amines which pose cancer risk. For that reason the European union has laid down legislation to prevent exposure to these hazardous amines. This implies that azo dyes containing aromatic amines can no longer be used to dye textile product that may come into contact with the skin. European union legislation specifically prohibits the use of 22 aromatic amines in a concentrate above the limit of 30 ppm.

Why do azo dyes contain amines?

Azo dyes contain one or more nitrogen-nitrogen double bonds called azo groups in their chemical structure, see Fig. 1.
-N=N –

Fig.1: Azo group

Under reductive conditions using sodium dithionite these azo groups can be cleaved to form 2 amines, which can be schematically shown as in Fig. 2.
Fig.2: Reductive cleavage of the azo dye to form amines
A small number of the aromatic amines are classified as being carcinogenic or potentially carcinogenic to humans. Only those few azo dyes that can release these amines upon reductive cleavage are affected.

Testing methods:
  • General Textiles: EN 14362-1:2003
  • Polyester : EN 14362-2:2003
It should be noted that if there are several color in the fabric, all the different color need to be tested. All the several colors should comply with this limit.

False positive result:
For certain dyed Fabrics a listed amine is detected under the conditions of the analytical test even though no banned azo dye is present in the garments. In our BUTEX lab they commercially tested AZO Group. The Test result of BUTEX lab are very reliable to Some international buyer like Marks & Spencer. They evaluated our campus so specially even they prefer the BUTEX Lab than other ISO accredited LAB such as ITS, SGS, BUREAU VERITAS etc in case of azo testing. But our testing equipment is not so updated. That conventional equipment detect the AZO group when it finds any nitrogen bond. It creates a confusion in the test result of BUTex lab and others. we expect more precision testing from the authority of BUTEX Lab in future.

List of Aromatic Amines according to EU directive 2002/61/EC: 
Sl. No.
Substance Name
CAS Number
01
Biphenyl-4-ylamin 4-aminobifenyl Xenylamine
92-67-1
02
Benzidine
92-87-5
03
4-chloro-o-toluidine
95-69-2
04
2-naphthylamine
91-59-8
05
o-aminoazotoluene4-amino-2’,3-dimethylazobenzene4-o-tolylazo-o-toluidine
97-56-3
06
5-nitro-o-toluidine
99-55-8
07
4-chloroaniline
106-47-8
08
4-methoxy-m-phenylenediamine
615-05-4
09
4,4′-methylenedianiline4,4′-diaminodiphenylmethane
101-77-9
10
3,3′-dichlorobenzidine3,3′-dichlorobiphenyl-4,4′-ylenediamine
91-94-1
11
3,3′-dimethoxybenzidineo-dianisidine
119-90-4
12
3,3′-dimethylbenzidine4,4′-bi-o-toluidine
119-93-7
13
4,4′-methylenedi-o-toluidine
838-88-0
14
6-methoxy-m-toluidinep-cresidine
120-71-8
15
4,4′-methylene-bis- (2-chloro-aniline)2,2′-dichloro-4,4′-methylenedianiline
101-14-4
16
4,4′-oxydianiline
101-80-4
17
4,4′-thiodianiline
139-65-1
18
o-toluidine2-aminotoluene
95-53-4
19
4-methyl-m-phenylenediamine
95-80-7
20
2,4,5-trimethylaniline
137-17-7
21
o-anisidine2-methoxyaniline
90-04-0
22
4-amino azobenzene
60-09-3
 



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