Restricted substances-Azo dyes

2 February 2009



Introduction Azo dyes used to be among the leading colouring agents in the textile industry, especially in developing countries. Since the 1990s, when legislation was introduced restricting certain azo dyes, there has been much confusion and misunderstandings concerning azo dyes. This article aims to clear these up.


Regulations for azo dyestuffs are actually for certain azo dyestuffs that produce amines classified as carcinogenic due to reduction decomposition. If absorbed by the human body, the azo dyestuffs may be changed due to the presence of enzymes systems with reduction properties. It is those dyestuffs that produce carcinogenic amines due to this reduction decomposition that are subject to regulations. Non fixed, water-soluble azo dyes can also come into contact with skin through perspiration fluid. 

Outline of the legislation

In order to prevent risks for consumers’ health, The European Commission published legislation that prohibits the marketing of textile and leather articles that come into direct contact with the skin which contain one of the hazardous amines. Indirectly, this legislation restricts the use of those azo dyes which can release one or more specified hazardous amines. This legislation is laid down in Directive 76/769/EEC on the marketing and use of dangerous substances and preparations and its amending Directives 2002/61/EC and 2004/21/EC on azo colourants.

 

Consumer goods affected

The latest amendment to the affected consumer goods refers to all ‘textile and leather articles which may come into direct and prolonged contact with the human skin or oral cavity’. The following examples are listed:

•clothing, bedding, towels, hairpieces, wigs, hats, nappies and other sanitary items, sleeping bags

•footwear, gloves, wristwatch straps, handbags, purses/wallets, briefcases, chair covers, purses worn round the neck

•textile or leather toys and toys which include textile or leather garments

•yarn and fabrics intended for use by the final consumer.

Azo dyes and pigments which fall within the scope of the regulation

A) Azo dyes

Those azo dyes are banned, which through cleavage of one or more azo bonds could form any of the twenty-two aromatic amines in the following list in concentrations above 30 ppm in the finished articles or in their dyed parts. Azo dyes are the most important chemical class of dyes, representing 60-70% of all dyes used. This Directive restricts the use of only about 5% of azo dyes.

List of amines included in the EC Directive 2002/61

Aromatic Amine

CAS number

4-Aminobiphenyl

92-67-1

Benzidine

92-87-5

4-Chloro-o-toluidine

95-69-2

2-Napthylamine

91-59-8

o-Amino-azotoluene

97-56-3

5-Nitro-o-toluidine

99-55-8

p-Chloroaniline

106-47-8

4-Methoxy-m-phenylenediamine

615-05-4

4,4-Methylenedianiline

101-77-9

3,3-Dichlorobenzidine

91-94-1

3,3-Dimethoxybenzidine

119-90-4

3,3-Dimethylbenzidine

119-93-7

4,4-Methylenedi-o-toluidine

838-88-0

6-Methoxy-m-toluidine

120-71-8

4,4-Methyl bis -(2-chloro-aniline)

101-14-4

4,4-Oxydianiline

101-80-4

4,4-Thiodianiline

139-65-1

o-Toluidine

95-53-4

4-Methyl-m-phenylenediamine

95-80-7

2,4,5-Trimethylaniline

137-17-7

o-Anisidine

90-04-0

4-Aminoazobenzene

60-09-3

 

Additionally, the following dye

Component 1: CAS-No.: 118685-33-9  C39H23ClCrN7O12S.2Na

Component 2:                                               C46H30CrN10O20S2.3Na

may not be placed on the market or used for colouring textile and leather articles as a substance or constituent of preparations in concentrations higher than 0.1 % by mass.

Also listed in Chinese legislation (GB 18401-2003) are the amines 2,4 Xylidine and 2,6 Xylidine. This states a limit for each listed amine in the product of 20ppm. The EU directive states a limit of 30ppm.

B) Azo pigments

The EU Directive does not contain any restrictions on azo pigments, and it is acknowledged that, due to their generally extremely low solubility, they do not pose a risk to consumer health. However, some azo pigments are sufficiently soluble under the analytical test conditions to yield detectable amounts of a listed amine (ie greater than 30 ppm consumer goods). For this reason some companies have screened to gather the amine content.

BLC recommends that a responsible approach should be taken to these pigments (amine content above 30 ppm consumer goods) even though they are not officially restricted by the Directive.

Official Methods

•CEN ISO/TS 17234:2003: Determination of certain azo colourants in dyed leathers

• EN 14362-1:2003: Textiles — Methods for the determination of certain aromatic amines derived from azo colourants — Part 1: Detection of the use of certain azo colourants accessible without extraction

•EN 14362-2:2003: Textiles — Methods for the determination of certain aromatic amines derived from azo colourants — Part 2: Detection of the use of certain azo colourants accessible by extracting the fibres

To determine the compliance with the EU Directive it is very important to ensure that an official method is used as many of the more aggressive test conditions applied by some contract laboratories tend to produce false positive results.

To ensure best compliance

Whereas the dye or pigment manufacturer is in a position to know which products are affected by these restrictions, it is the retailer or importer who is responsible for compliance. A textile finisher in Europe must also ensure that he does not use a banned azo compound for the manufacture of a regulated consumer item. The European Directive does not require any analytical testing. If the retailer can ensure by a certification procedure that banned azo colourants are not present, he can avoid substantial analytical costs.

To show due diligence an importer or retailer should:

Seek to exclude banned azo colourants from the manufacturing chain by establishing a formal certification procedure with his suppliers.

Ensure that suppliers of colourants to his manufacturing chain are fully conversant with the current regulatory requirements and can be relied upon to provide accurate information on their products.

Establish a formal system for checking compliance by testing an appropriate sample of affected consumer goods. The extent of this testing can be reduced as confidence is established, spot check testing can then be done to ensure compliance.

UK implementation

The restricted use of azo dyes in textile and leather articles as established in Directive 2002/61/EC and amended by 2004/21/EC was implemented in the United Kingdom by the Controls on Certain Azo Dyes and ‘Blue Colourant’ (Amendment) Regulations. The UK legislation is a direct transposition of the EU legislation. This means that the UK legislation sets the same requirements as the EU Directive. The table below provides a summary of the legislation.

 

Summary

Substance

(CAS

number)*:

Azo dyes that may split into harmful amines (92-67-1, 92-87-5, 95-69-2, 91-59-8, 97-56-3, 99-55-8, 106-47-8, 615-05-4, 101-77-9, 91-94-1, 119-90-4, 119-93-7, 838-88-0, 120-71-8, 101-14-4, 101-80-4, 139-65-1, 95-53-4, 95-80-7, 137-17-7, 90-04-4 and 60-09-3)

Products:

Textile and leather articles which may come into direct and

prolonged contact with the skin or mouth

Requirement:

Limit: 30 ppm

Status:

 

Existing implementation of EU legislation

Source:

The Controls on Certain Azo Dyes and "Blue Colourant" (Amendment)

Regulations

*A CAS number is a unique identifying number assigned to chemicals by the Chemical Abstracts Service.

For more information contact BLC Leather Technology Centre Ltd on info@blcleathertech.com or +44 (0) 1604 679999



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