Azo dyes in consumer products

An introduction to these substances which could pose a significant risk to human health.

Azo compounds (specifically azo dyes) are widely used in the footwear, furniture and fashion industries to dye natural textiles, synthetic textiles and leather. This is because they produce a huge variety of colours and provide good colour fastness properties, and so do not lose their colour or readily stain other fabrics. Azo dyes are not likely to be present in plastics or polymers such as polyurethane (PU) or polyvinyl chloride (PVC) as they are coloured using pigments rather than dyes.

Regulations

There are no restrictions on the use of azo dyes. However, certain aromatic amines which can be derived from azo dyes are carcinogenic and pose a significant risk to human health. These banned aromatic amines, of which there are 22, are restricted in Europe under REACH (Regulation (EU) No 1907/2006 Annex XVII entry 43) and in the UK under UK REACH, with the restrictions applicable to dyed leathers and textiles that come into contact with the skin. There are also four substances in REACH Annex XVII entry 72 that could undergo chemical reactions to form restricted aromatic amines:

• 4-chloro-o-toluidinium chloride could form 4-chloro-o-toluidine
• 2-naphthylammoniumacetate could form 2-naphthylamine
• 4-methoxy-m-phenylene diammonium sulphate could form 4-methoxy-m-phenylenediamine
• 2,4,5-trimethylaniline hydrochloride could form 2,4,5 trimethylaniline.

These REACH and UK REACH restrictions are applicable for textiles, with clothing and footwear specifically mentioned. Aromatic amines are also listed in California Proposition 65, so if they are present in products on sale in the state of California, warning labels need to be present at the point of sale.

How can I determine if aromatic amines are present?

The most common international testing standards to determine whether restricted amines are present are EN ISO 14362-1:2017 for textile materials and EN ISO 17234-1:2020 for leathers. The general principle behind the testing is to extract the dye from the material, to intentionally break down, or ‘cleave’, the azo dye into amines and then to ascertain if any of the specific banned amines are formed as a result of the reaction with the dye. Studies have shown that substances can migrate from clothing and leather articles which have been dyed with azo dyes. They may be absorbed into the body through the skin where there is direct and prolonged contact with the dyed material. Cleavage of azo dyes can occur ‘in vivo’ (in the human body) after skin absorption. The dyes may be broken down due to the presence of enzyme systems with reductive properties. Reductive conductions which facilitate the cleavage of the azo bond also occur in the human digestive tract and in some organs. Oral ingestion is also possible by workers manufacturing the dyes.

A vital assessment

Demonstrating that restricted aromatic amines derived from azo dyes are not present is mandatory for all consumer products sold within the EU and UK containing dyed textiles or leathers which may come in direct contact with the wearer’s or user’s skin. In order to ensure that consumer products comply with the requirements of the restriction, auditing of raw materials and production processes, the exchange of technical information throughout the supply chain and supplier declarations of conformity can provide information and assurance that banned amines are not present. SATRA can provide testing of azo dyes (banned amines) as a routine procedure and we have a wealth of experience to provide restricted substances advice and support to our customers.

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