In the following more detailed technical information will be given on those restricted substances relevant to leather and the related test methods and specifications.
Many tanners pass restricted substance lists (which they e.g. receive from customers/brands), together with specifications and test methods onto their chemical suppliers, asking them to guarantee that the chemicals comply with the same specifications as they must meet for the leather. That the specifications and test methods are specifically for leather is often not understood. The test methods listed in brand or manufactuerer RSL lists are in most cases only relevant for testing leather and not suitable for testing chemical products. Withouth specifiying and using the correct test method for a RSL substance test results are not reliable.
For example, requests to test dyes for formaldehyde (EN ISO 17226-2) and Cr(VI) (EN ISO 17075) using colorimetric test methods is simply not possible. Trying to determine the formaldehyde content in chemicals according to EN ISO17226-1 gives wrong results, since this test method requires an acidification to low pHs, causing the break-down and possible release of bound formaldehyde from the chemical. It is correct to acidify a water extract of the leather to determine the formaldehyde content, but it is not correct to acidify a chemical solution.
One commonly listed test method for heavy metals, EN 71-3, is a method for toys. What many do not realise is that the extraction process is made with a hydrochloric acid solution between pH 1.0 – 1.5, in order to simulate the conditions inside the human stomach. These very acid conditions are likely to extract some Cr from chrome-tanned leather and there could be difficulty for leather to comply with the extractable Cr limit. For extractable heavy metals the new method, EN ISO 17072-1, which uses a synthetic perspiration solution at pH 5.5, is a much more realistic and correct test for leather. Many brands and colabels have recognised that for clothes the synthetic perspiration extraction method at pH 5.5 (typically written EN ISO 105-E04) corresponds to the real-life situation and they use this extraction specification.
The JAMA test (issued by the Japnese Automotive Industry) involves sampling air from inside a car and this is now in the process of being formalised as an ISO Standard (ISO 12219-1). For those involved in supplying leather and other car interior materials, this is not a practical procedure for evaluating individual items. Several test methods for sampling air using samples in closed bags or chambers have been developed (i.e. TSM 0508G-2009, VDA 278) as more practical ways of analysing the emissions. At this stage there are still variations in the temperature, humidity and air flow between the different methods.
Most of the restricted substance lists show the required ISO or EN Standard to be used for making the test. However, with the rapid increase in the number of restricted substances, there is quite often no international leather method available and many simply list brief instructions like “solvent extraction, GC-MS”. RSL lists often give the test method used for water analysis, which ignores the most important aspect, namely the extraction step from leather. Leather is a complex matrix and the extraction must be validated between test laboratories.Some inter-lab trials have shown very large differences caused by different extraction procedures. Several test houses have their own internal test procedures, but until the procedures can be verified by inter-lab comparison trials, it is often difficult to validate such a method. The international ISO Standards are verified by validated inter-lab trials to check that the test procedure is robust and gives consistent results between laboratories.
The detection limits for test procedures should be based on inter-lab trials using the best available test procedures. Sometimes the limit is based on several factors, such as the extraction from a difficult matrix like leather, which causes background noise in chromatograms. Once the analytical result variability between labs exceeds 50%, then typically this is the detection limit for this method. Important is that the detection limits are not established using pure substances, since this ignores the critical impact of the leather extraction. Very important is that detection limits for test procedures are recognised and respected; recently there have been 2 cases of detection limits being reduced below what the test procedures can reliably measure. For example, the 30 mg/kg limit for aromatic amines in EN ISO 17234-1 was verified in several inter-lab trials. The analytical technique requires an extraction from leather and as well a reduction reaction to cleave the azo dyes and form the amines. The resulting complex matrix means that the background noise and interference from other extracted substances in the chromatogram was the key factor in establishing this 30 mg/kg limit. To find some restrictions now requesting a 20 mg/kg limit with the comment – we want to be sure we are under the 30 mg/kg limit of the EU – ignores the scientific logic for detection limits. Similarly, the EN ISO 17075 Standard for Cr(VI) in leather clearly explains that 3 mg/kg is the lowest reliable detection for the procedure. However, some restrictions now list a requirement to measure to 2 mg/kg and list the same test method – this is not possible! It must not be forgotten that it is not the detection limit of the reference sample in pure solvent that counts, but rather the detection in the leather extraction matrix, which can be a complex mix of side reactions and extracted materials that are removed from the leather.
The detection limits for test procedures should be based on inter-lab trials using the best available test procedures.
All around us there are traces of various chemical substances. Requests for exceedingly low levels of restricted substances can very often be close to or even below the levels found in nature. The leather industry uses water from rivers and wells, the chemical industry uses technical grade raw materials, so it is clear there will be natural levels for some restricted substances. Also often overlooked is that our natural raw material, namely the hides and skins, will also contain natural trace levels of restricted substances, for example, heavy metals. Some recent requests for lead (Pb) levels in leather of less than 0.1 ppm are probably lower than that typically found in the natural environment.
Here is listed some basic information about each of the restricted substances that could be relevant for leather. These substances or group of substances are the ones typically encountered and are not an exhaustive list of all restricted substances. The information below is only an overview and the individual regulations need to be consulted for full details. To help find the restricted substances quickly they are listed in alphabetical order.
Listed at the end of this section are several substances and substance groups that are not relevant for leather, but are still very often requested.
Acetaldehyde recently attracted a lot of attention by car makers particularly in the Asian automotive market. In GB/T 27630-2011 (the Chinese Regulation) limits for acetaldehyde emissions from car leather are set to be 0.2 mg/m3 which is extremely low and far beyond any health risks. Acetaldehyde is not being used in the manufacture of any leather chemical product and even if present in trace amouts in chemical products those do not contribute to the acetaldehyde readings. It has to be assumed that acetaldehyde is continuously formed by oxidation or fermatation of certain substances (fats, sugars, etc.) but also during the testing.
The only way to achieve above low levels is the use of a scavenger product. TFL has developed the product A 3210 which can be used in Wet-end and finishing applications to suppress acetaldehyde formation.
TFL does not use any of the above types of allergic or sensitizing dyes in their leather dye range of: SELLA® Cool, SELLA® Derm, SELLA® Fast, SELLA® Star, SELLAFLOR®, SELLASET®.
Azo dyes are some 90% of all leather and textile dyes. Azo dyes break down under reductive conditions to form aromatic amines.
The EU Regulation specifies in Appendix 10 the test method for each type of substrate and in Annex XVII defines the detection limit of 30 mg/kg for each amine in leather. The official test method for leather is CEN ISO/TS 17234; this method is now updated and replaced by EN ISO 17234-1. Until now Ecolabels and brands have used the EU limit of 30 mg/kg, however;
Careful: A small number of Ecolabels restrict 2 additional aromatic amines that are not forbidden. Some test houses measure the presence of the forbidden amine, 4-aminoazobenzene, by analysing for the 2 amines, 4-aminoaniline (p-phenylene diamine) and aniline, both which are not forbidden.
Depending on the reduction conditions it is possible that for the widely used black dye, C.I. Acid Black 210, some 4-nitroaniline is reduced to 4-aminoaniline, which can lead to test houses giving a false positive result for 4-aminoazobenzene. The new method, EN ISO 17234-2 should be used for testing leather for 4-aminoazobenzene.
All TFL dyes (SELLA® Cool, SELLA® Derm, SELLA® Fast, SELLA® Star, SELLAFLOR®, SELLASET® ) do not contain azo dyes made with the forbidden amines. Most commercially available azo dyes do not break down to give these forbidden amines.
The EU Directive 98/8/EC, Biocidal Products Directive (BPD), controls and regulates the use of biocides, they are not part of REACH. Registration of a biocide is very expensive and only a few active biocide substances are expected to be available for the leather industry in the near future.
Biocides are applied to raw hides & skins (bactericides) and in pickling/tanning (fungicides) to stop the leather being damaged during transport and storage. Some of the chlorinated phenol type of biocides are now restricted. Only a few fungicides dominate the leather industry usage. The big 4 fungicides are commonly known by their abbreviations, for example, PCMC (para-chlor-meta-cresol), OIT (2-n-octylisothiazolin-3-one), OPP (ortho-phenylphenol), TCMTB(2-(thiocyanomethylthio) benzothiazole).
The Ecolabel, “Der blaue Engel” (the blue angel), gives recommendations for allowable limits in leather of the active fungicide components: PCMC < 300 mg/kg, OIT < 100 mg/kg, OPP < 500 mg/kg and TCMTB < 500 mg/kg.
Biocides are also used to stabilise chemical products that contain natural or biodegradable substances. These can be susceptible to bacteria or fungi attack. However, the quantity of biocide that would then be applied to the leather with the chemical is some 100 to 1000 times less than is applied to protect leather in the Beamhouse process.
Biocides found often in waste water emissions from tanneries are not only from products used during leather manufacture but can also derive form the animal raw hides where pesticides etc. are being used for protecting animals from diseases.
TFL uses biocides which comply with the EU Biocidal Product Directive and the ‘Blue Angel‘ (Blauer Engel) issued by German Enviornmental Ministry.
Boric acid and disodium tetraborate, commonly called borax, have recently been notified as candidates in the SVHC decision making process. They are classified as toxic for reproduction. These boron compounds are widely used in many industries and if they do become SVHC substances, then their limited use in some leather industry processes will need to be replaced.
Boric acid is used in some deliming formulations and borax has been used in small amounts in leather chemical formulations to adjust the pH and penetration.
Leather made with the international range of TFL leather chemicals would comply with the SVHC requirements.
A group of polybrominated flame retardants are restricted. They are used in plastics. (They are not water soluble so not suitable for wet-end leather applications).
SELLA® Tec products from TFL used for fire protection do not contain polybrominated organic flame retardants.
Short chained chlorinated paraffins (SCCP) are those with a chain length of C10–C13. EU Regulation 1907/2006 (formerly as EU Directive 2002/45/EC) restricts the marketing and sale of SCCP in preparations to a maximum of 1% (= 10 000 mg/kg). Analytical methods to determine SCCP in leather are still being developed. Currently there is no validated test method available.
Note: The medium chain MCCP (C14–C17) and long chain LCCP (C18–C30) chlorinated paraffins are not restricted by EU Regulation nor by the ZDHC Leather MRSL list. The presence of MCCP must be listed in the EU-Safety Data Sheet.
The international range of CORIPOL® fatliquors from TFL comply with the EU Regulation restricting SCCP.
Chlorinated phenols were previously used extensively to inhibit mould growth. The 3 chlorophenols listed are now forbidden in consumer products:
The detection level of 5 mg/kg has become the accepted limit using the EN ISO 17070 test method for leather.
TFL does not use PCP, TeCP and TriCP in the TFL range of leather chemicals.
The hexavalent chromium oxidation state (Cr(VI)) is allergenic and carcinogenic if inhaled and thus restricted by the EU. The detection limit is 3 mg/kg in the leather test method, EN ISO 17075. This is the level generally accepted for Cr(VI) in leather. Some Ecolabels and brands try to be one step better and specify 1 or 2 mg/kg, but they list the same test method. This is not correct as the ISO Standard method includes information clearly pointing out how the 3 mg/kg detection limit was established. Lower detection limits cannot be justified with this technique.
The Cr-containing chemicals used in the manufacture of leather are all based on Cr(III). However, during manufacture it is possible that traces of Cr(VI) can be formed if certain measures in the the application process are not properly followed. Most important are good removal of natural grease, avoidance of fatliquors with high content of unsaturated fats and any oxidising agents. Use of vegetable tannins and anti-oxidants help to suppress the formation of Cr(VI) whereas low humidity and high temperature can trigger their formation particularly in the presence of unsatured fats. Cr(VI) is one restricted substance where, through the choice of the application process, the tanner is responsible for avoiding its presence.
The Cr(VI) oxidation state does not form organic complexes, so dyes based on stable organic Cr(III)-complexes do not form Cr(VI) in the leather. Careful: Analyses for total Cr measure all the oxidation states of chromium. This technique cannot be used to determine the Cr(VI) content.
The Cr-containing TANNESCO® syntans from TFL contain only Cr(III) salts, no Cr(VI) is present.
The use of the product SELLASOL® C6 in the last step of wet-end operations helps to eliminate the presence of any Cr(VI) in the leather. SELLASOL® C6 can also retard or prevent the formation of Cr(VI) during transport or storage. Post formation of Cr(VI) however can not be ruled out especially if an excess amount of unsaturated fats are present.
Dimethyl fumararte is a solid, which sublimes to a gas. It has good anti-fungal properties, so it has been used in sachets inside the packaging for sofas, shoes and boots, especially those items being exported from Asia to Europe. Dimethyl fumarate is an allergic sensitizer at low concentrations and can cause severe skin rashes and irritations. Since 2009 the EU has forbidden the marketing of any products containing dimethyl fumarate. It is not used as a biocide for leather, the problem was caused by the inclusion of dimethyl fumarate inside the packaging and it depositing on the surface of the consumer goods.
Careful: Dimethyl fumarate is commonly referred to as DMF in publications and the media. It should not be mixed up with the solvent dimethyl formamide that chemists have traditionally called DMF.
TFL does not use dimethyl fumarate in any of the TFL leather chemical products.
Formaldehyde is used extensively for making industrial chemicals. For example, in the leather industry many syntans are formaldehyde polymers. Once the formaldehyde has reacted it is no longer present as formaldehyde. Some small residues of unreacted formaldehyde can occur in a few products, typically melamine resins and some cationic dye fixing agents. Different analytical procedures are used to measure the free unbound formaldehyde and the hydrolysable formaldehyde (only released by interaction with water). For leather used in automotive seats the free formaldehyde test (emission into air) is important. For leather in shoes with skin contact the water extraction method determines the free and hydrolysable formaldehyde.
Careful: Select the correct analytical methods for leather:
The SELLATAN® and SELLASOL® syntan products are either low formaldehyde or formaldehyde-free (for both the free and hydrolysable formaldehyde). Trace levels are listed in separate TFL Statement of restricted substances. With suitable application processes, leather can be prepared to comply with the very low residual formaldehyde requirements given above. For example, by using a syntan like SELLATAN® WL-W and the auxiliary syntans SELLASOL® HFN, SELLASOL® FTF or SELLASOL® MI, it is possible to make leathers that are free of residual formaldehyde. The MAGNOPAL® polymer retanning agents are free of formaldehyde.
EU limits for heavy metals in consumer items have been introduced via the EN Standard for extractable heavy metals in toys. In the USA the CPSC sets levels for heavy metals in consumer items. The EN 71-3 method has defined the following maximum limits for extractable heavy metals:
The low pH extraction process could make it difficult for chrome-tanned leather to comply. Ecolabel limits for heavy metals are often much lower and normally they also specify total metal. For example, some textile Ecolabels set very low limits for total Cr. Obviously achieving these lower levels is not possible with Cr-tanned leather. Other Ecolabels, such as the SG Label, accept chrome-tanned leather and restrict only the extractable Cr and Cr(VI).
Careful: Check if the specification is for extractable or total metal content and check which extracting agent is specified!
Often there are requests from certain brands for metal-free leather. Such request should be specified for ‘free of toxic heavy metals’ since presence of non-toxic metals can be critical to achieve certain performances (e.g. high light fastness of metal dyes. Metal-free leather according to EU guidline is specified as as containing less than 0.1 % of Cr(III), Al, Ti, Zr, Fe.
Other than Cr(III), TFL is not adding the above heavy metals (As, Cd, Cr, Hg, Pb, Sb, Ba, Se) to any TFL product. Metal content of TFL dyes and pigments are listed in separate TFL Statement of Restricted Substances.
Some dyes are organic metal complexes of either Cr(III), Co, Cu or Fe. This information is listed in section 12 of the TFL Safety Data Sheet. The TFL dyes and pigments also comply with the stringent ETAD guidelines for heavy metals.
N-methyl pyrrolidone (NMP) has been extensively used as a high boiling point solvent and flow-improver in finishing formulations. In the Californian Proposition 65 legislation, NMP was classified as toxic for reproduction. In the EU, the classification has now been changed to toxic for reproduction and from the end of 2010 any product formulation containing quantities of NMP above 0.1% must list this in the Safety Data Sheet. Most brands and automotive manufacturers now do not allow the use of NMP in finishing products.
No product in TFL range uses NMP and NEP (N-ethylpyrrolidone).
The EU Regulation requires that nonylphenol (NP) and nonylphenol ethoxylate (NPE or NPEO) are not to be used in preparations at levels greater than 0.1% during leather (or textile) processing if the waste water is discharged. The generalised form of these type of substances is written as APEO (alkylphenol ethoxylate). Until recently the nonylphenol ethoxylates were used extensively as non-ionic surfactants and emulsifiers in the textile and leather industry. In Europe they have now been replaced by alternative surfactants. In order to show NPEO containing preparations have not been used, Ecolabels can require less than 100 mg/kg in leather.
The TFL international range of BORRON® surfactants are not based on nonylphenol ethoxylate.
TBT (tributyl tin), DBT (dibutyl tin) and MBT (mono-butyl tin) are restricted chemicals. These are used as antimicrobals, e.g. in paints for boats. Tin compounds can be used as catalysts in the production of PU polymers. Trace levels of organotin compounds may be present in PU finishes but after application they will be fixed.
TFL does not add restricted organotin compounds to any leather chemical product.
The fluorochemicals based on C8 chemistry, eg. PFOS (perfluorooctane sulfonate) has been found to be persistent in nature so it has been forbidden. The EU Regulation limits PFOS to 0.005 % by mass in consumer goods. Analytical methods are complicated and an ISO method still in development. The corresponding acid form, PFOA, is usually also restricted by brands and Ecolabels. The same applies for chemicals based on C6 Fluor Chemistry. Fluorochemical products based on C4 chemistry have by far the lowest degree of bioaccumulation and toxicity among all fluorochemical products. Nevertheless some of the brands have decided to completely restrict the use of PFC.
TFL does not have PFOS or PFOA in the fluorochemicalproducts it supplies. TFL fluorochemicalproducts are all based on C4 chemistry.
Some RSL lists regulate the content of free phenol.Phenol is used in the manufacture of polymers(synthetic tanning agents) and as in the caseof formaldehyde trace amounts can be found insome of these products.
Some TFL products from SELLATAN®, SELLASOL®range contain traces of free phenol resulting fromthe polymerisation process. Trace level amountsare listed in the separate TFL Statement of RestrictedSubstances.
Phthalates6 phthalates (DINP, DEHP, DNOP, DIDP, BBP andDBP) are restricted in the EU. These are used assoftening agents in plastics to give it the requiredflexibility. The EU Regulation limits individualphthalates to 0,1% (= 1000 mg/kg) in chemicalpreparations.
Ecolabels and leather shoe manufacturers typicallyset limits of < 500 mg/kg total phthalates inleather.
TFL does not use the restricted phthalates in theleather chemical products.
Polycyclic aromatic hydrocarbons (PAH) arepresent in tar oils. These typically dark colouredextracts are used as cheap softening agentsin rubber and some plastics. It is most unlikelythat they would be used by the leather industry.Naphtalene, the most simple PAH substance, isnot intentionally used in leather manufacture butpresent in trace level in some dispersing products.
TFL does not use PAH substances intentionally inleather chemical products. Naphtalene can, however,be found in trace levels in some dispersingagents. Levels are listed in separate TFL statementfor Restricted Substances and do not exceed anyallowable limits of major RSL and MRSL.
Substances of Very High Concern (SVHC) are animportant new part of the REACH Regulation(EU 1907/2006) in the EU. After a consultancyprocess and risk evaluation, those substances thatare considered to be SVHC will be listed in AnnexXIV of the EU Regulation. Currently there are168 chemical substances in the SVHC candidatelist, but at present none have yet been assignedSVHC status in Annex XIV which would then meanthat substances could not be generally used andneed authorisation for a particular use. Each EUmember country can introduce substances (withsupporting documentation) for the candidatelist. After this, the candidate substances undergoa risk assessment process before the decisionis made about becoming a SVHC substance inAnnex XIV. The risk assessment evaluation is animportant step in judging the potential harm ofchemical substances.
Consumer articles, e.g. leather, containing morethan 0.1 % of a SVHC substance will not be allowedto be imported into the EU region. Presence of a SVCH substance in chemcials products at levelshigher than 0.1 % needs to be declared and user needs to be informed by the chemicals supplier on its safe use. The current 168 candidate SVHC substances, except for the recently announced boric acid and disodium tetraborate, are not likely to be used by today’s leather industry.
As soon as a chemical substance is put on the candidate list many brands and Ecolabels react immediately restricting the use of the candidate substance. From a legal point of view, candidate chemicals can still be used and in many cases the residual amount in leather may not exceed 0.1 %. In the manufacture of active TFL sales products no SVHC substance is being used.
Volatile Organic Compounds (VOC) refer to organic solvents, especially those with a boiling point between 50°C – 260°C. If present, these organic substances can be emitted into the air during leather production, especially in the finishing process. The EU regulates the amount of VOC output that can be emitted into the air with respect to leather manufacture. The automotive and upholstery industries place restrictions on the VOC emission from leather. Both industries have different test methods and requirements. The VOC is measured by heating the leather in a closed chamber and the individual emitted VOC substances are determined by a mass spectrometer (i.e VDA 278 test method ) The results can be influenced by the time since the leather was made and the storage method. The Very Volatile Organic Compounds (VVOC) are those with a boiling point below 50°C. The semi-volatile organic compounds (SVOC) have boiling points between 260°C – 400°C. VOC emissions of special interest coming from leather are formaldehyde, acetaldehyde, benzene, toluene, xylene, ethylbenzene, styrene, acrolein, NMP and NEP and these are all including various RSL and regulations.
By using TFL products it is possible to comply with the total VOC emission requirements for above mentioned substances set by brands, Ecolabels and OEM’s.
Some tanneries give to their chemical suppliers long lists of restricted substances that they have received from their customers. Many of the listed substances have effectively no relevance for the leather industry of today. For many of them the only reason for listing seems to be for completeness and perhaps to make additional tests. Typical non-relevant substances for leather are asbestos and blue colorant. The EU Regulation 1907/2006 (formerly in EU Directive 2003/03/EC) bans the use of a “blue colorant”, Index No. 611-070-00-2. According to current knowledge this forbidden blue colorant has never been sold to the worldwide leather industry. No samples of the dye have been able to be located so it is not possible to analyse for this colorant.
Preserving agents for the short-term preservation of fresh hides and for soaking.
A range of surfactants and degreasing agents, as well as sequestering agents. High efficiency, tailor-made products for all process steps.
A range of fatliquoring agents based on natural and synthetic fatty substances.
The TFL range of products suitable for use in the finishing of leather in all types of manufacturing processes.
A range of selected dyes that comply with the TFL Cool System requirements. They do not absorb radiation in the near-infrared, which restricts the rise of temperature on the leather surface when it is exposed to sunlight.
A range of concentrated solutions of homogeneous, salt-free, mainly metal complex dyes in water-miscible and environmentally acceptable organic solvents.
A large range of acid and direct dyes for the coloration of leather where good levelness, covering power, brilliance, shade consistency and good Fastness properties are required.
A compact range of special acid dye mixtures to produce various brown, beige and olive shades, featuring good general Fastness properties.
A group of leather chemical products suitable for manufacturing flame retardant leather.
A range of 1:2 metal complex acid dyes especially suitable for trichromatic dyeing systems.
A range of auxiliary syntans for the retanning of leather.
Our products are all comply with highest standards regarding hazardous substances and and environment sound production.
Considering the many possible substances of concern, one may ask how safe leather really is and how safely it can be made?
The simple answer is: Leather made with state-of-the-art technology and chemicals is a very safe product. It is possible to manufacture leathers that comply with the most stringent requirements as to restricted substances and no health risks can be associated with such leather, which is formed from a natural product.
This requires that manufacturers take care to select the appropriate processing chemicals and apply them correctly. TFL has been pioneering the area of ecological leather manufacturing through the development of various innovative product technologies. One example of them is the TFL White Line Technology which complies with the very stringent SG Label standards. White Line leathers have been tested by dermatologists on highly sensitive test persons and found not to cause any allergenic reaction.