Disperse dyes and footwear
An examination of hazards linked to the use of these substances.
by Lucy Cove
Image © © iStockphoto.com | Vladimir Sukhachev
A wide range of products, including footwear, clothing and upholstery, rely upon the use of disperse dyes to produce coloured textiles. However, there are growing concerns that these substances can have adverse effects upon human health, which has led to new restrictions being placed upon their use in consumer products within Europe. In response, SATRA has produced a new internal test procedure called ‘The Quantitative Analysis of Disperse Dyes by LC-MS’.
What are disperse dyes?
‘Disperse dyes’ are a group of small, insoluble molecules which can be ground into a dispersing agent and supplied as a paste or spray to textile manufacturers. They were originally developed for the dyeing of cellulose acetate, but are now used to colour a range of synthetic textiles, including nylon, polypropylene, polyester and acrylic. Some disperse dyes can exhibit poor colourfastness, meaning that they are more likely to transfer colour onto skin or other fabrics with which they come into contact. Because of this, poor colourfastness of a textile may be an indication that disperse dyes have been used in its production.
Concerns regarding the use of disperse dyes in consumer products were first recorded following the introduction of nylon stockings to the US market in the 1940s. Soon after their launch, a link was observed between women wearing the new brown stockings and allergic irritations. Initially, these reactions were attributed to a ‘nylon allergy’, but further investigation proved that dyes used in the nylon were responsible. It is now estimated that approximately 5 per cent of the population can suffer from an allergic reaction to certain disperse dyes – usually in the form of an itchy rash localised to the area of contact. However, tolerance to exposure is highly variable, and some individuals may experience more severe symptoms, including swelling and blistering of the skin.
In addition to causing allergic reactions, a number of disperse dyes can have more severe and long-term effects on human health. There are ten disperse dyes which are classified as carcinogens, meaning that repeated exposure may lead to the development of cancer. A list of known allergenic and carcinogenic disperse dyes is provided in table 1.
|Table 1: Allergenic and carcinogenic disperse dyes|
|Allergenic disperse dyes||CAS number|
|Disperse blue 3||2475-46-9|
|Disperse blue 7||3179-90-6|
|Disperse blue 26||3860-63-7|
|Disperse blue 35||12222-75-2|
|Disperse blue 102||12222-97-8|
|Disperse blue 106||12223-01-7|
|Disperse blue 124||61951-51-7|
|Disperse brown 1||23355-64-8|
|Disperse orange 1||2581-69-3|
|Disperse orange 3||730-40-5|
|Disperse orange 37/76||12223-33-5/13301-61-6|
|Disperse red 1||2872-52-8|
|Disperse red 11||2872-48-2|
|Disperse red 17||3179-89-3|
|Disperse yellow 1||119-15-3|
|Disperse yellow 9||6373-73-5|
|Disperse yellow 39||12236-29-2|
|Disperse yellow 49||54824-37-2|
|Allergenic and carcinogenic dyes||CAS number|
|Disperse yellow 3||2475-45-8|
|Carcinogenic dyes||CAS number|
|Acid red 26||3761-53-3|
|Basic red 9*||569-61-9|
|Basic violet 3*||548-62-9|
|Basic violet 14||632-99-5|
|Direct black 38||1937-37-7|
|Direct blue 6||2602-46-2|
|Direct red 28||573-58-0|
|Disperse blue 1*||2475-45-8|
|Disperse orange 11||82-28-0|
|Other dyes listed in Specifications||CAS number|
|Disperse yellow 23||6250-23-3|
|Disperse orange 149||85136-74-9|
|* Disperse dyes restricted to less than 50mg/kg under REACH Regulation (EC) No. 1907/2006 Annex XVII entry 72.|
Despite the health concerns associated with the use of disperse dyes, until recently there were no European-wide restrictions on their use in consumer products. In October 2019, three carcinogenic disperse dyes were included within REACH Regulation (EC) No.1907/2006 Annex XVII entry 72. This restricts the use of these disperse dyes to a maximum concentration of 50mg/kg in textiles, to apply from 1st November 2020.
In addition to the inclusion of these three carcinogenic disperse dyes within REACH Annex XVII, there are a number of other restrictions on the use of disperse dyes in consumer goods. These include the German Food and Feed Code (LFGB), which restricts the amount of all the disperse dyes detailed in table 1 to less than 75mg/kg for each dye. Several disperse dyes are also included within California Proposition 65, and these are listed in table 2. Although these dyes are not restricted, a warning label is required at the point of sale if they are present in products placed on the market in California.
|Table 2: Disperse dyes listed in California Proposition 65|
|Disperse dye||CAS number|
|C.I. Basic red 9 monohydrochloride||569-61-9|
|C.I. Disperse yellow 3||2832-40-8|
|D&C red no.9||5160-02-1|
|Direct black 38 (technical grade)||1937-37-7|
|Direct blue 6 (technical grade)||2602-46-2|
|Disperse blue 1||2475-45-8|
|HC blue 1||2784-94-3|
As well as legal restrictions, many footwear and clothing brands will have their own specifications which restrict the use of disperse dyes in their products. It is essential that clear and thorough communication throughout the supply chain is maintained in order to meet such brand specifications.
How can we help?
There are a number of test methods which can be used to determine the presence of disperse dyes in footwear and clothing textiles. The techniques are all very similar, with the colourants being extracted from the textile into a suitable solvent before being quantified using liquid chromatography with mass selective selection (LC-MS). The previously-mentioned SATRA test procedure, based upon DIN 54231, has been developed to quantify the amounts of a wide range of disperse present in synthetic textiles. Please email email@example.com for further details.
This article was originally published on page 22 of the September 2020 issue of SATRA Bulletin.