1. How to stop the Chromium VI
to get enter into leather
Presented by: Abdul Satter
Manager Training SRC
Hotel the Jeeven
2. 1. Need to understand Some basic terms.
2. Formation and Health Hazards of chromium VI
3. Recommendation for Chromium (VI) Avoidance.
4. Product available in market to inhibit the chrome VI in leather
5. Screening system for post-production / during shipment.
6. Testing procedures and protocols.
3. FREE RADICAL
Free radicals are short-lived, highly-reactive intermediate products which
can develop through a reaction with oxygen.
Free radicals can for example be fat residues in leather which has not
been degreased carefully and which therefore triggers a chain of
reaction which leads to an increasing number of free radicals.
Free radical can promote the development of Chromium (VI).
Free radicals can be caught through antioxidants and thus made
Antioxidants are therefore known as radical catchers.
4. IODINE COUNT
The iodine count is the measurement used to measure how unsaturated a
Fats with high iodine counts contain a lot of double bonds.
Fat liquors with iodine counts within a range of 5-20 are ideal.
Fish oils have iodine counts of between 100 and 200.
IODINE-STARCH PAPER TEST
Test of the oxidative potential by using potassium iodine starch paper (oxidation
The oxidative potential is indicated through blue discoloration of the test strip.
5. UV RADIATION
The main source is the sun (Normal day light,) but also UV lamp and
fluorescent tubes also emit UV rays.
UV radiation is not visible and is high in energy.
In leather UV rays can lead to formation of extremely reactive substances
and free radicals, through which Chromium (VI) formation is promoted
Gain of oxygen. Or loss of hydrogen /electrons during chemical reaction
Loss of oxygen or gain of hydrogen / electrons.
Latin word meaning "to lead back.“
Takes electrons from that other substance or Gives oxygen to another substance
i.e. An oxidizing agent oxidizes something else.
Examples of oxidation/Reduction Reaction-
fire, the rusting, the browning of fruit, and respiration and photosynthesis etc.
7. Antioxidant (Reducing agent)
Removes oxygen from another substance i.e. An Reducing agent reduce something
Oxidation- a chemical reaction that can produce free radicals and chain reactions
Antioxidants are compounds that inhibit oxidation (Antioxidants are considered
free radical scavengers/ catchers)
Vegetable tannins- commonly used in the leather industry (Mimosa, Quebracho,
Sumac, Tara, valonea and chestnut) and Sugar,etc
The results show that gallotannins within the hydrolysable tannins have taken
the first places in ranking with superior antioxidant activities
Based on sulfer and phosphonium – Sodium bisulfite and tetrakis-
9. POSSIBLE SOURCES OF HEXAVALANT CHROMIUM
Unreduced chromium present in the leather auxiliaries are the direct source of
Basic Chromium Sulfate (BCS) used as a main tanning agent
Chrome syntan and chrome Alam syntan
Certain class of metal complex dyes
Inorganic pigments (Particularly in the case of pigments based on lead
Apart from the direct sources many tools, substances, auxiliaries, chemicals and
process parameters could contribute significantly to the conversion of trivalent
chromium into hexavalent chromium. e.g;
Exposure to direct sunlight or quick drying in heat chambers.
Application of Ammonia or Ammonium bicarbonate prior to the dyeing process.
10. POSSIBLE SOURCES OF HEXAVALANT CHROMIUM
Chromium III tanned leather can generate traces of Chromium VI when
exposed to certain environmental conditions (heat, UV radiation, changes in
pH) or in the presence of unsaturated organic compounds and oxidizing agents
Heat and adhesives in shoe production promotes the formation
of chromium VI.
Leathers with a higher proportion of tannin chromium (III) are more prone to
the formation of chromium (VI) than a leather with a lower chromium (III)
There is evidence that the amount of free chromium is one important
Parameter for the formation of Cr(VI) in leather
Too low humidity during storage greatly accelerates the chromium VI
If stored for a long duration, the leather should be tested for chromium VI.
11. CHROMIUM VI FORMATION MECHANISM:
Chromium-VI has sometime been detected in chrome tanned leathers and it is
unexpected because chromium-VI is not stable in the presence of high
proportion of organic matter at low pH.
It is widely investigated & believed that auto oxidation of Cr -III to Cr-VI in
leather is catalyzed by temperature and ultraviolet radiation during drying or
intermediate drying process.
In the presence of heat & UV radiations the atmospheric oxygen attacks the
double bonds in various leather auxiliaries already used in crusting & dying
process which results in formation of unstable and highly reactive peroxide
molecules. These radicals further react with other double bonds and start a
free radical chain reaction and this chain reaction provides a favorable
environment in which chromium-III can easily be changed in to chromium -VI.
12. HEALTH HAZARDS OF CHROMIUM VI
Chromium (VI) is known to cause various health effects. When it is a compound
in leather products, it can cause allergic reactions, such as skin allergies,
dermatitis and ulcerations.
The most common way of human body penetration by the chromium
compounds is through inhalation into the lungs.
Hexavalent chromium causes lung cancer in humans.`
Hexavalent chromium can irritate the nose, throat, and lungs. Repeated or
prolonged exposure can damage the mucous membranes of the nasal passages
and cause ulcers to form.
Hexavalent chromium is very irritating to the skin. Prolonged contact can cause
ulcers to form. Some workers develop an allergic sensitization to chromium.
Hexavalent chromium is an eye irritant. Direct eye contact with chromic acid or
chromate dusts can cause permanent eye damage.
Weakened immune systems, Kidney and liver damage, Alteration of genetic
13. Specification/Label Application Limit
EN 420:1998 Standard Leather Protective Gloves 2mg/Kg
European Eco-label Footwear 10 mg/Kg
Textiles, Leather Undetectable
Oko-tex 100 Label
(Detection level:0.5 mg/kg)
Textiles, Leather Undetectable
SG Label Textiles, Leather, Paper,
LGR Label Leather Undetectable
EUROPEAN ECO-LABEL FOR FOOTWEAR. VARIOUS
LIMIT LEVELS PRESCRIBED BY DIFFERENT
INSTITUTIONS ARE PRESENTED HERE UNDER.
14. Check the pH values during the individual process steps
Liming & De-liming
Reduce the excessive use of ammonia and ammonium salts.
Wash the limed hides carefully after liming and de-liming.
Avoid products with oxidative potential, e.g. peroxide, permanganate or
If using these products, check the oxidative potential with iodine-starch paper
and if necessary, reduce the oxidation agent using a reducing agent prior to the
addition of chromium
Degreasing is of utmost importance for the oxidation behavior of leather.
Remove natural grease, which otherwise oxidize generating reactive peroxide
lipids and eventually Cr(VI).
Carefully degrease the raw skins/raw hides
Use aqueous degreasing agents (Based on Fatty Alcohol)and ensure sufficient
removal of the naturally occurring residual fat, which possesses an oxidative
The fattier sheep leather are more susceptible than cowhide.
RECOMMENDATION FOR CHROMIUM (VI)
15. RECOMMENDATION FOR CHROMIUM (VI)
Chromium (VI)-free agents—Use Cr(VI) free tanning Agents and
chemicals, tested for Cr(VI) and procured from a reputable supplier.
Bleaching agents - Avoid or reduce the bleaching agents used prior to the
tanning process and never use bleaching agents after tanning.
Basification-Ensure as complete a fixation of the Chrome tanning agent as
pH Values- Carefully check the pH values during the individual process steps
Check the pH value of the Chrome tanning liquor if it is to be re-used; this
should lie below pH 4.
Recycled Chrome tanning agents - Do not use self-recycled Chrome
tanning agents without prior inspection for Chromium (VI) (e.g. EN ISO 19071)
Only use recycled Chrome tanning agents from preparation companies who are
able to guarantee that their products are free of Chromium (VI
16. RECOMMENDATION FOR CHROMIUM (VI)
Avoiding Cr-retannage reduces the risk of Cr(VI) formation. Since this is in many
cases not possible.
Wash the wet-blue carefully after re-chroming to remove excess of free Cr(VI).
Neutralizing agents—Use neutralizing auxiliaries (Neutralizing /Dispersing
syntans )with reduction capability in neutralization and wetting back of crusts.
Use Neutralizing Syntans to avoid over-neutralization and give at the same time
a good homogeneity of the pH in the cross-section of the leather.
Avoid chemicals containing ammonia during neutralizing.
pH Values- Higher the pH in neutralization, the higher will be the risk of Cr(VI)
formation in the finished leather.
Neutralize leather materials to the lowest possible pH value and avoid pH peaks
(Maintain pH below 6.5) during neutralization
Washing - Avoid the accumulation of free chromium on leather surface by
washing after the neutralizing.
17. RECOMMENDATION FOR CHROMIUM (VI)
Colorants –Dyes & Pigments
Do not use pigments or dyes that contain chromium if possible as chromium-
based colorants and/or chromium-based after-treatments may cause these
materials to exceed established Cr (VI) limits.
Chromium-based colorants available in the market should be carefully checked
to ensure compliance.
Use dispersing Syntans during purging and dying Instead of Ammonia or
ammonia containing chemicals.
Vegetable tanning agents specially Tara and Sodium thiosulfate (HYPO)works
like sun block and protect the leather to react with heat and UV radiation during
exposure to sun.
Add antioxidant chemicals in the re-tanning process (e.g., Use 1-4% vegetable
tannins) to provide additional protection against oxidation.
18. RECOMMENDATION FOR CHROMIUM (VI)
The influence of free fatty acids in fat liquors cannot be ignored so never use fat
liquors with a high proportion of unsaturated fatty acids, such as fish , animal or
vegetable oils -sulfonated and sulfited fish oils and others like natural and
blended oils having free fatty acids more than 10%
Use fat liquors with oxidation protection, synthetic fat liquors and/or softening
polymers from certified manufacturers.
Use fat liquors that are oxidation-stable.
Finish the wet process (Crusting) and ensure Final fixing thoroughly by Formic
acid at pH 3.5~4.0 by running more.
Reducing agents—Use reducing agents such as sodium bisulfite, Sodium
thiosulphate, Sodium meta-bisulfite may be used in the final washing of leather.
Oxidizing agents—Use Do not use aggressive bleaches; Peroxides and
Potassium permanganate (KMnO4) as bleaching agents after tanning.
The pH value of the crust should lie below pH 5, ideally at pH 3.5-4
Such treatments may alter the shade and color intensity of the leather and
hence accordingly the process of dyeing needs to be re-standardized
19. RECOMMENDATION FOR CHROMIUM (VI)
Where feasible, carry out an Batch washing with emulsifier during /after process
to wash out any free Chrome & natural fats in leather.
Ageing (piling) plays an important role in process as more time is required to
complete the reaction while water is being removed from leather.
Perform mechanical operation on leather only after conditioning with water
(Moisture level 14-17%).
Avoid the formation of mold over the entire process.
Preserve wet blues and dyed leather with sufficient amounts of biocidal agents
that have been certified for the purpose
20. RECOMMENDATION FOR CHROMIUM (VI)
Final Finishing /Finish
Use suitable chemicals from certified manufacturers from safe sources
Do not use finishing agents with alkaline adhesive coatings
Do not use dyes and pigments that contain Chromium
Use suitable finishing products (e.g. colors and coatings) which ideally feature
Avoid excessively high temperatures during final finishing
Preservation during Storage & transportations in
Avoid storage and transport of leathers in air polluted heavily with oxidizing
gases like ozone, nitrogen oxides and sulfur oxides.
During transport, manufacture and use of leather items, avoid prolonged
exposure to low humidity, high temperatures and direct sunlight.
Avoid heating chrome-tanned leather to apply prints or set adhesives.
Check the leather for Chromium (VI) contamination after prolonged storage
Post-production checks—after prolonged periods of storage, check leather for
post-production formation of chromium (VI).
21. RECOMMENDATION FOR CHROMIUM (VI)
Risks of chromium VI in the whole life cycle of a leather product must be
Water-repellent leather, leather in darker shades and vegetable re-tanned
leather are less likely to result in formation of chromium VI, compared
to split leather or bright leather.
Perform risk-based checks of your suppliers’ materials via testing from
third-party lab to ensure the Cr(VI) limits are not exceeded.
Every fail report with values falling into 3-5 mg/kg range, should be re-
confirmed by a different third party Lab.
Note: There is also an EU regulation that places an upper limit of 1
mg/kg for Cr(VI) in textile articles.
Consider applying the ageing test to leather samples. This step will
artificially age the leather in conditions that will drive Cr(VI) generation
This will give some indication of how your leather goods will fare under
22. RECOMMENDATION FOR CHROMIUM (VI)
Require suppliers to submit a confirmation of material compliance or a
test report from a third-party laboratory that is experienced in analyzing
the specific matrix.
23. Evolite S-87
Composition: Fatty Alcohol Ethoxylate
Appearance: Colorless To Slightly Yellowish Transparent Liquid
Concentration: Active =75% ±1
pH: 7 ± 1
Properties: Environment Friendly, Highly Effective Degreasing,
Excellent Dispersing of Natural Fats with Low Fogging value,
Compatible with acid, alkali, electrolytes and polyvalent cations
Washing ability for Fur Skins.
Recommendations: highly effective emulsifying & Degreasing
system with an all-purpose field of application.
24. Resolan UF
Composition: Fatty Alcohol Ethoxylated
Appearance: Opaque Thick Paste
pH: 8 ± 1
Properties: High degreasing power
High concentration, Provides clean and smooth grain, Prevents
chrome soap formation in the wet blue and Compatible with
Recommendations: high efficiency degreasing agent for hides
25. Resolite 1907
Composition: Synergistic mixture of surfactants & Organic
Appearance: Yellowish Transparent Thick Liquid
Concentration: Solids: 45±1
Properties: soaking, liming, de-liming and degreasing agent It
has a buffering effect against sudden swelling and good soaking
Helps in good water absorption even without over milling
during soaking, liming making the hair removing action more
efficient and flattening the wrinkles giving a more relaxed and
nice looking pelts
Recommendations: soaking, liming, de-liming and degreasing
26. Resolite W
Composition: Ethoxylated product
Appearance: Pour able paste
Concentration: Solids: 45±1
pH: 5.0 - 8.0
Properties: Very effective wetting & degreasing, Provide clean
wool and grain, Biodegradable and Compatible with
electrolytes. In bating and de-liming helps to disperse and
dissolve the heavy soluble liming chemicals. Having good
natural fat dispersing property. Gives fine, smooth grain and
Recommendations: Effective wetting and degreasing agent.
27. RESOCROME A (with antioxidant property)
RESOCROM A Basic chromium sulphate reduced
with SO2 having Cr2O3 26 +0.5% with 33% basicity.
RESOCROM A powders are readily soluble even in
cold suitable to be used in powder form
Thanks to excellent penetration and even distribution
of RESOCROM powders gives full & bright wet blue,
suitable for dark as well as pastel colors and white
28. FORMECO AO (With antioxidant property)
High in strength, 25% less consumption than Formic acid
Regulates the pH during tanning without altering the strength
Gives more smoothness to grain as these products maintain the polymer structure of leather
Thanks to their post process properties the wet blue shows excellent leveling during re-tanning
and dying with more elastic, fine, round, smooth and tight grain with improved tensile and tear
FORMECO AO has excellent antioxidant properties minimize the risk of Chromium VI formation
in leather during storage.
Products gives more depth and uniformity to dyes due to their excellent Fixing property,
Less acid retention after washing
Health and Environmental Benefits
Safe to handle and does not burn the skin
Eco-Friendly product for leather processing
Reduce the effluent treatment cost
29. ECOTAN CROM VI Antioxidant
Composition : Derivative of Monosaccharides
Appearance : Slightly Reddish Transparent Liquid
Concentration: Active 12 ± 0.5%
Compatible with acid and Alkali bath
Free of organic solvents and phenolic derivatives,
Suitable for wet end & Finishing application as it forms no film owning to
its chemical nature
1. Recommended for Wet Blue, Crusting & Dyeing up to 0.5-1.5%.
2. Dilute the product with water and spray on flesh of leather. Quantity
can be adjusted as per requirement.
3. Dry the leather, after drying; keep at room temperature for
overnight to complete the reaction.
30. Quick test chromium VI content
Study of rapid tests in 2016
Provide too many false results due to the complexity of the test materials and the
objects to be scanned. Estimated future chemistry is partially highly corrosive; the
durability of the DPC reagent is of very short duration; the study is carried out
only on the surface of the leather which result in falsified results; dyes in leather
can interfere with the visibility of the pink color (chromium VI) and the chemistry
used can potentially destroy the material. This concludes that a quick test is not
on a par with professional laboratory tests.
RECOMMENDED TESTING PROCEDURES AND PROTOCOLS.
31. Limitation in test methods
EN 17075 is the official test method for Cr-VI in leather. This method specifies
“No Detection” of Cr-VI at the detection limit of 3 ppm. Some eco labels
demand maximum 1 or 2 ppm Cr-VI using the same test method - but
technically lower detection limits are not justified with this test method.
Remedies for such sensitive limits and harmonization
among various test houses
A method developed by CLRI using Ion-Chromatography after membrane
separation of colorants is gaining recognition with reproducibility and reliability
at more than 95%. This method overcomes the shortcomings associated with
the official test protocol with reference to both false positive and false negative
32. CHROMIUM (VI) CONTENT-----
– Inspection for maintenance of the legal limit value:
Chromium (VI) in leather is determined on a cut sample according to EN ISU
17075 standards after extraction.
The direct determination of the Chromium (VI) content in the leather matrix is
not currently possible.
The quantity of the Chromium (VI) found in the extract is calculated back to the
content in the leather.
The verification limit of the procedure is 3mg/kg Chromium (VI) per kg leather.
The conditions stipulated in the standard for the extraction must be adhered to
strictly, otherwise there is a risk of a false-positive result.
An extraction of composite samples for the determination of Chromium (VI) is
not recommended, as it can lead to false results if one leather sample is
contaminated with Chromium (VI), but the other features a reductive potential
33. CHROMIUM (VI) AGING……
– Inspection for the formation of Chromium (VI) during the
leather aging process:
Under laboratory conditions, thermal aging is simulated on the leather.
To do this, the cut sample is stored according to the CADS methods at 80°C and
with relative air humidity of up to 5% for 24h in a drying cabinet without
ventilation, air circulation or any openings to the outside. Subsequently, the
Chromium (VI) determination according to the EN ISO 17075 standards takes place
as described above
34. CHROMIUM SOLUBLE
– Inspection as to whether a leather sample releases larger
quantities of soluble Chromium under wearing conditions:
Chromium soluble is mainly tested on leather samples which may come into
contact with the skin during the intended application of the respective leather
product. In this test approach, wearing conditions are simulated which provide
information on the possible Chromium release under realistic conditions. The
determination takes place according to EN ISO 17072-1 after extraction of the
leather with an acidic perspiration solution at 37°C.
35. TOTAL CHROMIUM CONTENT
– Inspection of whether leather has been chromium tanned or has
been through a chromium-free tanning process:
For the measurement, the leather is completely dissolved according to EN ISO
17072-2 or 5398 Part 1-4 (total disintegration process). The total chromium
content of chromium is a piece of leather. Based on this data, conclusions can
be drawn concerning the tanning method used. In case of a total Chromium
content of below 1000mg/kg, the leather is classified as chromium-free tanned
leather according to EN 15987.
36. If any query Please contact our office……………
SRC Pvt. Ltd.
Shop No 12-13 Chaudhary Plaza Haji Pura Road
E-Mail: Sialkot @src.com.pk
Mr Hafiz Badar (0300-8471262)
Mr Tahir Munir (0301-8406155)
Mr Haseeb Zahid (0322-5707322)