Azo dyes are organic compounds, which contain the colouring azo function (N=N-). The azo function is often bound to an aromatic ring, and the dye can then be broken down to an aromatic amine, arylamine. This can take place either chemically, through 'reductive cleavage', or through the body's own enzyme system. Some azo dyes can also be broken down to arylamines during storage due to light and high temperature. Some arylamines have been judged to be carcinogenic. The best known one is aniline. It is important to remember that not all azo dyes are based on arylamines.
Azo dyes are used in dyeing textile fibres, particularly cotton but also silk, wool, viscose and synthetic fibres. They are considered to be easy to use, relatively cheap and to provide clear, strong colours. There are approximately 2000 azo dyes on the market.
The majority of azo dyes are water-soluble and are therefore easy for the body to absorb, and this takes place through inhalation and swallowing of dust as well as through skin contact. Azo dyes may also be toxic to aquatic organisms and cause long-term adverse effects in the aquatic environment.
It is likely that the arylamines emitted from the azo dye can be absorbed by the skin and accumulate in the body. There is a risk of exposure when wearing garments or accessories that contain azo dyes, or when sleeping in such bedclothes. Some of the arylamines are also judged capable of producing allergy on skin contact, irritating the eyes, being toxic by inhalation and if swallowed or being very toxic by inhalation, skin contact and if swallowed. Some of the arylamines have also been judged to be toxic or very toxic to aquatic organisms and to be capable of causing long-term adverse effects in the aquatic environment, here you can search in the classification list.
Within the EU, the treatment of certain textile articles and leather articles with azo dyes that can release carcinogenic arylamines has been prohibited, see Directive 2002/61/EC.
Chemicals in textiles – Risks to human health and the environment. Report of a government assignment. KemI Report 3/15. In Swedish with an English summary on page 11. Swedish Chemical Agency, 2015.
Kemikalier i textilier – redovisning av ett regeringsuppdrag (Chemicals in textiles – report on a government commission). KemI Report 2/97, Swedish Chemicals Inspectorate, 1997.