Red-Listed Textile Dyes: Examining Health Hazards and Risks

Red-Listed Textile Dyes: Examining Health Hazards and Risks

Environmental protection and product safety are becoming increasingly important criteria in the purchase of textiles, due to the emotive nature of the debate and greater consumer concern. This article provides general information about azo dyes to help put the issue on a more factual basis. Here you will also find some background notes about the German Consumer Goods Ordinance (GCGO), together with a list of banned amines. Information is also provided about the test methods used for evaluating presence of Azo dyes in textiles.

Eco Label Criteria: Key Pollutant Parameters for Textile Producers

The major pollutant parameters being considered for issuance of eco label to a textile producer are as follows:

Azo dyes containing Banned Amines and Toxic heavy metals

The excess heavy metal transfused through porosity of skin can lead to organ failure like lever, kidney & intestine, disordering nervous system with genetic disability. It can affect many metabolism functions that bring in poor health issues.

Toxic pesticides

Cotton cultivation is directly linked to the use of pesticides. The pesticides are harmful to human body and also severely affects soil fertility due to their non- biodegradable nature.

PCP -penta chloro phenol & Halogen carriers

PCP is stable to natural degradation. In humans its bio-accumulation takes place & posses severe health-hazards. Similarly chlorine bleaching and use of other organo halogens compounds as carriers are also regarded as unsafe due to their toxic nature

Free formaldehyde

Formaldehyde a pungent smelling chemical is a skin irritant and sensitizer and causes dermatitis and respiratory problems. Higher proportion of formaldehyde is nasal carcinogen.

Ph extract of the substrate

Ph extract is not within range and limits then human skin is susceptible towards highly acidic or alkaline condition. Irritation and allergies can be caused if pH is not within limits.

Color fastness

Leaching out of dyestuffs is non desirable due to its direct contact with human body. The banned amines start reacting with the skin and poses threat to the human health very rapidly.

Inducing poisonous dye particle through perspiration and rubbing against the skin can be controlled by very good fastness properties of the fabric.

Azo reduction can be accomplished by human intestinal micro flora, skin micro flora, environmental microorganisms, to a lesser extent by human liver azo-reductase, and by non-biological means.  Some azo dyes can be carcinogenic without being cleaved into aromatic

amines.  However, the carcinogenicity of many azo dyes is due to their cleaved product such

as benzidine.  Benzedrine induces various human and animal tumors.  Another azo dye component p-phenylenediamine (p-PDA) is a contact allergen.  Many azo dyes and their reductively cleaved products as well as chemically related aromatic amines are reported to affect human health, causing allergies and other human maladies.  

Azo compounds are chemically represented as R–N=N-R’, where –N=N- is the azo group, and the R or R’ can be either aryl or alkyl compounds. The International Union of Pure and Applied Chemistry (IUPAC) defines azo compounds as “derivative of diazene (diimide), HN=NH, wherein both hydrogens are substituted by hydrocarbyl group, e.g. PhN=NPh  azobenzene or diphenyldiazene”

Azo dyes are compounds consisting of a diazotized amine coupled to an amine or a phenol and contain one or more azo linkages. The essential precursors of azo dyes are aromatic amines.

Azo compounds have vivid colors and comprise about two-thirds of all synthetic dyes and are by far the most widely used and structurally diverse class of organic dyes in commerce.  Azo dyes are the largest and most versatile class of dyes and account for more than 50% of the dyes produced worldwide

Azo dyes are stable in light and resistant to microbial degradation or fading away due to washing. Therefore, azo dyes are not readily removed from waste water by conventional waste water treatment methods.  It has been estimated that about 10%-25% of the dyestuff in the dyeing process of textiles does not bind to fibers and are, therefore, released to the environment.

Mechanism of actions:-

Reductive cleavage:-

Azo dye Aromatic amine
R-N=N-R’ = R-NH₂ + NH₂-R’

1. Anaerobic condition (which can work without oxygen but use oxygen if it is present)
2. Reductive chemical medium
3. Enzymatic process (biological reducing agent intracellular as well as intestinal bacteria are responsible for reduction in body)

Factors affecting human health: –

The factors which affect human health may be intrinsic or extrinsic.

Intrinsic: – Malfunctioning of human immune system of the body, genetic disorder, and harmon imbalance are called intrinsic

Extrinsic: –Those infused from outside human body like disease causing microorganism & chemical/dye pollutant are called extrinsic. They affect the health by interfering with health functiong of the body.

Covalent bonding with DNA

The high electron density in the ring of aromatic amines makes electron removal very easy so they are easily oxidized and below 7 ph are converted into R-NH⁺, which form covalent bond with nucleic acid of DNA causing DNA damage. They induce mutation in DNA and living cells. These mutations may occur in germ cells and may results in altered structure or function of the cells & thus they interfere with the formation of normal cells in the body and form abnormal cells. Abnormal cells ultimately lead to formation of tumors or cancers. Since these amines are insoluble in water they may get accumulated in bladder and induce bladder cancer.

The following 20 aromatic amines are listed in the German Consumer Goods Ordinance. All are also listed in Group III of the MAK list under Category 1 or 2:

Aromatic amines

1. 2-naphthylamine
2. 4-aminodiphenyl
3. 4-chloro-o-toluidine
4. benzidine
5. 2,4,5-trimethylaniline
6. 2,4-diaminoanisol
7. 2,4-toluenediamine
8. 2-amino-4-nitrotoluene
9. 3,3’-dichlorobenzidine
10. 3,3’-dimethoxybenzidine [3,3’-dianisidine]
11. 3,3’-dimethyl-4,4’-diaminodiphenylmethane
12. 3,3’-dimethylbenzidine [o-tolidine]
13. 4,4’-diaminodiphenylmethane
14. 4,4’-methylene-bis-(2-chloroaniline)
15. 4,4’-oxydianiline
16. 4,4’-thiodianiline
17. O-aminoazotoluene
18. O-toluidine
19. p-chloroaniline
20. p-cresidine
21. O-anisidine  
22. p-aminoazobenzene.

Consumer goods according to section 5, No. 6 of the German Food and Consumer Goods Law, textile consumer goods are defined as “articles which have more than a passing contact with the human skin”. The Consumer Goods ordinance defines this more precisely

1. Garments; fabrics and yarn used to produce garments

2. Bedding; bed linen and blankets; pillows; sleeping bags

3. Towels; beach mats

4. Masks; hairpieces; artificial eyelashes

5. Jewelry worn against the skin; bracelets

6. Neck purses; rucksacks

7. Items on which babies and small children lie or sit

8. Diapers; sanitary towels; panty liners; tampons

(Source: Consumer Goods Ordinance 5^th amendment)

The Azo dye extract is analyzed for the 20 listed amines using one of the following methods: –

• Thin layer chromatography (TLC)
• High-performance liquid chromatography (HPLC)
• Gas capillary chromatography (GC)  
• Capillary electrophoresis (CE)