Flame retardants are chemicals that are usually added intentionally to textile or footwear articles to meet legal and contractual flammability standards.1 By adding these chemicals the finished article’s ability to ignite is reduced. Flame Retardants are typically not used in day to today fashion clothing.
The common uses for flame retardants are; electric and electronic equipment (i.e. TV sets and personal computers), the construction industry, the transport industry.2 Textile applications focus on furniture upholstery, carpets and curtains for public buildings like theatres and cinemas, automotive/aircraft/trains interior textiles, certain personal protection workwear e.g. for fire fighters.
Historically, flame retardants have been applied to textiles during processing. Leather and footwear articles are rarely equipped with flame retardants. Flame retardants can be applied as a back coating or by the padding method.
Flame retardants can be applied directly, as blends or as a topical finish. These days flame retardants are typically used in very specialised technical applications such as firefighting or military gear and protective clothing.
There are a lot of various species of inorganic and organic chemicals based on halogen, phosphorous and nitrogen compounds that can provide flame retardant properties to articles. In view of the big variety of these chemicals it is not possible to assign general toxicological properties to the whole range of flame retardants.
However, certain brominated flame retardants have been linked to endocrine disruption and thyroid dysfunction.3 Some of the organophosphate chemicals used as flame retardants could pose a risk to bone and brain health.4
Polybrominated diphenyl ethers (aka PBDEs) are scrutinised for its delayed mental and physical development and reduced fertility.5
Tetrabromobisphenol A (TBBPA), which is used in plastic paints, synthetic textiles and electronic devices is known to cause cancer and therefore proposed for harmonised classification in EU CLP as well as included in the EU SVHC Candidate List since January 17th, 2023.6
Apart from this, many of the organic flame retardants are considered persistent and are known to bioaccumulate inside living organisms.7
The ZDHC MRSL V3.1 lists a total of 32 chemicals under the flame retardant category. Apart from this SCCPs and MCCPs, chemicals put under the heading of chlorinated paraffins are also known to be sometimes used as flame retardants. All these chemicals can be classified into three groups.
Flame retardants interfere with the combustion process (e.g. during heating, decomposition, ignition of flame spread). The way they achieve this could be by;8
Inorganic flame retardants are essentially the inorganic salts used for their properties of being flame retardants. Some of the inorganic flame retardants that are banned from intentional use in textile and footwear manufacturing as per the ZDHC MRSL V3.1 are listed below:
| Chemical | CAS No. |
|---|---|
| Boric acid | 10043-35-3 / 11113-50-1 |
| Diboron trioxide | 1303-86-2 |
| Disodium octaborate | 12008-41-2 |
| Disodium tetraborate anhydrous | 1303-96-4 / 1330-43-4 |
| Tetraboron disodium heptoxide hydrate | 12267-73-1 |
Organophosphorus flame retardants are the most widely used category of flame retardants in textiles. These could be phosphates or phosphine oxides. The list of organophosphorus flame retardants banned from intentional use as per the ZDHC MRSL V3.1 are listed below:
| Chemical | CAS No. | Notes |
|---|---|---|
| Trixylyl phosphate | 25155-23-1 | |
| Tris (2,3 dibormopropyl) phosphate | 126-72-7 | Also classified as halogenated |
| Tri (2-chloroethyl) phosphate | 115-96-8 | Also classified as halogenated |
| Tris (2-chloro-1-methylethyl) phosphate | 13674-84-5 | Also classified as halogenated |
| Tris (1,3-dichloroisopropyl) phosphate | 13674-87-8 | Also classified as halogenated |
| Tris (1-aziridinyl) phosphine oxide | 545-55-1 | |
| Trimethyl phosphate | 512-56-1 | |
| Tri-o-cresyl phosphate | 78-30-8 | |
| Bis(2,3-dibromopropyl)phosphate | 5412-25-9 |
Halogenated organic flame retardants are the biggest class of the flame retardants used in textiles. These flame retardants can be further classified as either chlorinated flame retardants or brominated flame retardants. Many halogenated organic flame retardants are notoriously known for their persistence in the environment and bioaccumulation in living organisms. Therefore, there are for many years concerns about the risk/benefit ratio for these chemicals pose to public health for its application. The following list of chemicals from the ZDHC MRSL V3.1 are banned from intentional use in textile, leather and footwear industries.
| Chemical | CAS No. |
|---|---|
| 2,2-Bis(bromomethyl)-1,3-propanediol | 3296-90-0 |
| Decabromobiphenyl | 13654-09-6 |
| Decabromodiphenyl ether | 1163-19-5 |
| Dibromobiphenyls | Multiple cas nos |
| Heptabromodiphenyl ether | 68928-80-3 |
| Hexabromocyclodecane | 3194-55-6 |
| Hexabromodiphenyl ether | 36483-60-0 |
| Monobromobiphenyls | Multiple cas nos |
| Nonabromodiphenyl ether | 63936-56-1 |
| Octabromobiphenyls | Multiple cas nos |
| Octabromodiphenyl ether | 32536-52-0 |
| Pentabromodiphenyl ethe | 32534-81-9 |
| Tetrabromobisphenol A | 79-94-7 |
| Tetrabromobisphenol A bis (2,3-dibromopropyl ether) | 21850-44-2 |
| Tetrabromodiphenyl ether | 400088-47-9 |
| Tribromodiphenyl ethers | Multiple cas nos |
The flame retardants used in the textile and leather industries are highly selective and application specific. Therefore, it is still a challenge to find an exact match to replace them with less hazardous chemicals. However, if alternatives are found to be effective in textile or leather applications, it is recommended that a case-to-case study and a phase-out process is carried out to replace the current usage of these ZDHC MRSL restricted substances.
Any alternative selected must be carefully vetted to ensure a regrettable substitution is not made. Including checking it is conformant to the latest version of the ZDHC MRSL. In the past many regrettable substitutions were tried and therefore any new substitution needs to be tested on several levels before it can be deemed safer.
In certain cases where flame retardants are used in polymers, it is recommended to be incorporated during the polymerisation steps, reducing the chances of it leaching into the environment. However, the overall hazard and possible leaching still needs to be tested. Following table lists some of such chemicals that have been proven to be effective as flame retardants.
Because of their hazardous properties, flame retardants are highly regulated chemicals covered by global legislation:11
In general all flame retardants used in textile, leather, footwear, or other chemicals need to conform to the latest version of the ZDHC MRSL.
The use of the flame retardants listed in the ZDHC MRSL V3.1, or any halogenated flame retardant, is not permitted (for fashion, sport or outdoor clothing and apparel and home textiles).
It should be noted that there are certain critical (e.g. technical textile) end uses where legally or contractually mandated standards may only be achieved using these substances (e.g. military, medical, protective clothing, public transportation and public buildings). The formulations will always be deemed ZDHC MRSL NON-CONFORMANT and it is intended that the ZDHC Supplier Platform will appraise the end uses of any flame retardants within an inventory.
| EPA | Environmental Protection Agency |
| GHS | Globally Harmonised System |
| MCCP | Medium-chain chlorinated paraffins |
| MRSL | Manufacturing Restricted Substances List |
| SCCP | Short-chain chlorinated paraffins |
