Banned Azo Dyes Testing

1. Introduction to Banned Azo Dyes

Certain azo dyes used in the printing and dyeing of workwear. Carcinogenic aromatic amine dyes that can decompose refer to dyes that, under certain conditions, break down into carcinogenic aromatic amines through reduction reactions. These decomposable carcinogenic aromatic amine dyes belong to the azo dye category, with their molecular structures containing an azo group (—N=N—). Not all azo dyes are hazardous; only those that produce carcinogenic aromatic amines pose risks to human health. Currently, the number of recognized carcinogenic aromatic amines domestically and internationally is 24, involving approximately over 200 azo dyes. It should be noted that azo dyes are the most numerous type among synthetic dyes, characterized by a wide color spectrum, complete color range, good color fastness, and high color durability. They are widely used in dyeing various fibers. Banned azo dyes account for only about 5% of all azo dyes, meaning not all azo dyes are prohibited.

With the release of the EU regulations banning azo dyes and the implementation of China's mandatory national standard GB 18401—2003 "National Technical Specification for Basic Safety of Textile Products," decomposable carcinogenic aromatic amine dyes have become one of the most critical monitoring indicators in the international and domestic production and trade of textiles and apparel.

2. Hazards

Banned azo dyes are a small subset of azo dyes, which are widely used in the market for dyeing textiles, apparel, leather products, and more. Textiles, clothing, or other consumer goods dyed with decomposable carcinogenic aromatic amine dyes, after prolonged contact with human skin, may undergo reduction reactions under the biochemical conditions of normal human metabolism, breaking down to form carcinogenic aromatic amines. These can alter the DNA structure of human cells through a series of activation processes, leading to diseases and inducing cancer.

3. Testing Standards

Unlike formaldehyde, which is easily identifiable and soluble in water, decomposable carcinogenic aromatic amine dyes in textiles are insoluble in water, colorless, and odorless, making them impossible to detect by appearance alone; they can only be identified through technical testing.

Currently, gas chromatography and liquid chromatography are primarily used to detect banned azo dyes. Relevant domestic testing standards include GB/T 17592-2011 "Textiles—Determination of Banned Azo Dyes" and GB/T 23344-2009 "Textiles—Determination of 4-Aminoazobenzene," among others. Generally, testing is first conducted according to GB/T 17592. If aniline and/or 1,4-phenylenediamine are detected, further testing is performed according to GB/T 23344.

Additionally, China's mandatory national standard GB 18401-2010 "National Technical Specification for Basic Safety of Textile Products" prohibits the use of decomposable carcinogenic aromatic amine dyes in textile products, with a limit value for carcinogenic aromatic amines set at ≤20 mg/kg.

4. Related Standards

GB/T 17592—2006 "Textiles—Determination of Banned Azo Dyes"

ISO/TS 17234:2003 "Leather—Chemical Tests—Determination of Certain Azo Dyes in Leather"

EN 14362—1:2003 "Textiles—Methods for Determination of Certain Aromatic Amines Derived from Azo Colorants—Part 1: Detection of the Use of Certain Azo Colorants Accessible Without Extraction"

EN 14362—2:2003 "Textiles—Methods for Determination of Certain Aromatic Amines Derived from Azo Colorants—Part 2: Detection of the Use of Certain Azo Colorants Accessible by Extracting the Fibres"

German Standard §35LMBG82.02—2 "Analysis of Consumer Goods—Testing of Textile Consumer Goods for the Use of Certain Azo Dyes"

German Standard §35LMBG82.02—3 "Testing of Consumer Goods—Detection of Banned Azo Dyes in Leather"

German Standard §35LMBG82.02—4 "Analysis of Consumer Goods—Testing of Polyester Fibers for the Use of Certain Azo Dyes"

German Standard DIN 53316:1997 "Testing of Leather—Determination of Certain Azo Dyes in Leather"

GB/19601-2004 "Limit and Determination of 23 Kinds of Banned Azo Dyes in Dye Products"

GB/T 23344—2009 "Textiles—Determination of 4-Aminoazobenzene"

GB/T 24101—2009 "Limit and Determination of 4-Aminoazobenzene in Dye Products"