Consequences of banning chromium VI in leather articles

26 October 2012

(The full article is published including tables is published in October, 2012 Leather International magazine page 48-52)IntroductionOn March 16, 2012 the ECHA (European Chemicals Agency) launched a six-month public consultation on the proposed restriction on chromium VI (Cr VI) in leather articles. This was in response to a request from the Danish authorities proposing a restriction on leather articles containing Cr VI, in concentrations above 3mg/kg, which come into contact with the skin. The European Commission is expected to make a decision on whether to introduce these restrictions into the REACH Regulation by March 2013.

I argue that it is vital that this proposed restriction should not be introduced. I consider that the proposal for REACH to ban leather articles which, contain more than 3 mg Cr VI/kg is out of proportion to the problem of chrome allergies caused by leathers. Also, Cr III and Cr VI both elicit dermatitis at low concentrations but this has not been addressed in the proposed restriction. Before any restriction is considered there should be substantial further investigation into:

  • Managing chrome allergies to leather items
  • Control of Cr VI formation in finished leather
  • A viable substitute for chrome in shoe leathers
  • Consequences of the restriction throughout the world
  • The likely effect of the restriction on chrome allergies

Approximately 80% of global leather production is tanned with chromium III (Cr III) salts. Over 0.2% of the European population is said to be sensitive to chromium but chrome tanned leather has been worn for over 100 years and this sensitivity has been known but managed. Some Cr VI must always have been present in chrome leathers. Tanners and others who are allergic to chromium use barrier creams, made from ascorbic acid (vitamin C) and EDTA, and cortisone ointments to control dermatitis. People allergic to shoes can wear barrier socks and those allergic to chromium can wear synthetics if necessary.

The best leathers for shoes and many other items are chrome tanned. When white tannages are used for shoe leathers, they are usually retanned with chromium. Allergy to Cr VI is a greater problem than allergy to Cr III, but Cr III sensitivity is also a problem. Cr VI sensitivity is caused by sodium dichromate and other compounds, which are widely used; a REACH restriction on leathers will not overcome Cr VI sensitivity. Also a Hansen (2006) study has demonstrated that elimination of Cr VI in leather would not overcome chrome allergies to leather.

If Europe introduces this regulation then the world leather industry will be severely threatened. There is, at present, no viable alternative to chrome in shoe leather and there is no viable way to ensure elimination of Cr VI from chrome tanned leather articles.


Peanut allergy is estimated to affect about 1% of children and adults worldwide and is a far worse allergy than Cr VI. Peanut allergy is one of the most common causes of food-related death. However, peanuts are not banned but are avoided by those allergic to them. It is far more difficult to avoid eating products containing peanuts than to avoid contact with chrome tanned leathers.

The problem of allergic contact dermatitis in perspective

The extensive Warshaw NACDG study of allergic contact dermatitis (ACD) found that 17.5% of patients allergic to shoes were allergic to Cr VI. (Warshaw et al., 2007).

The North American Contact Dermatitis Group (NACDG) patch-tested 10,061 patients between 2001 and 2004. Among the 109 NACDG patients with dermatitis of the foot, and a shoe source of allergens, the adhesive p-tertiary butylphenol formaldehyde resin was the most common allergen, accounting for 24.7% of positive patch-test results, followed by potassium dichromate (Cr VI) (17.5%) and carba mix (11.7%). When the data were examined according to groups of allergens, rubber chemicals (40.4%) were the most frequent allergens, followed by adhesives (32.5%), and leather components (20.1%).

This study found that about 1% of ACD patients were allergic to shoes and 0.2% were allergic to leather components. ACD is a major problem but Cr VI is only one of several shoe allergens. Fungicides can also be shoe allergens.

Hanson et al. 2003 found that although most studies investigating chromium allergy have been performed with Cr VI, both Cr III and Cr VI are capable of eliciting eczema at low concentrations. It was concluded that rather than regarding chromium dermatitis a result of Cr VI allergy alone, it may be more correct to consider it as a result of a combined Cr III and Cr VI allergy.

Hansen’s 2006 results show that the proposal of Cr VI < 3 mg/kg is unlikely to overcome the dermatitis problem with chrome tanned leather.

In the Hansen 2006 study to determine the relation between the content of Cr III and Cr VI in leather and to elicit leather dermatitis in chromium (VI) positive patients, fifteen chromium-allergic patients with past or present foot eczema and suspected leather relevance were patch tested with 14 chromium-tanned leather samples and a vegetable-tanned control leather sample. The content of chromium (VI) in the samples was in the range of < 3 mg/kg and 16.9 mg/kg determined using the DIN 53314 method. The leather sample eliciting a reaction in the highest number of patients was the one with the lowest content of both Cr VI, < 3 mg/kg, and soluble Cr III, 12mg/kg, (Hansen et al., 2006 a).

This study is of particular relevance because it tested leather samples and showed that 50% of the allergic reactions were caused by leathers with Cr VI < 3 mg/kg.


Five patients reacted to leathers, which contained less than 3mg Cr VI/kg and no patients reacted to the two leathers with the highest Cr VI contents. Therefore, the proposed restriction is very unlikely to control the ACD problem with chrome tanned leather.

Controlling Cr VI in leathers

Considerable research has determined processes to be used to produce leather containing less than 3mg Cr VI/kg, and these processes are now used in Europe. However, Cr VI can be generated in these leathers during storage and use. Cr VI is formed in chrome tanned leathers during manufacture of articles, exposure to heat, low humidity, daylight and UV light. Ageing tests are available but do not simulate the real ageing of leather over months rather than days.

Replacement of chrome tannages

There is now a range of alternative tannages but chrome tanned leathers are usually superior, less expensive and more versatile. This is why 80% of leather is chrome tanned. When white tannages are used for shoe leathers, they are often retanned with chromium.

Prevention of formation of chromium (VI) in the further processing and storage of leather

There are serious problems with this section of the ECHA proposal. It appears that there is not yet a proven, acceptable method to control Cr VI formation during storage, transport and ageing of leathers, manufacture of footwear and ageing of manufactured products. Antioxidants have been tested but and their effectiveness in controlling allergies not been demonstrated. Also, it is known that ascorbic acid causes unacceptable discolouration of aged leathers.

Problems with the proposed systems are demonstrated in studies cited in the ECHA proposal.


Although the antioxidants lowered the Cr VI content in these leathers, this may increase to detectable levels with longer ageing at different temperatures and humidity and longer daylight or UV irradiation. This will be the case with many leathers in retail conditions and in use. It should also be noted that the antioxidants greatly increased the soluble chromium in the leathers and levels over 700 and 1500 mg/kg may cause skin reactions (Hanson et al. 2006 b). Also, Cr VI could be generated from this soluble Cr III during subsequent storage.

It is stated, page 72 in the ECHA proposal, that the humidity of the environment during storage of the leather has been demonstrated to have a significant effect on the formation of chromium (VI) in the stored leather. The higher the humidity, the lower the chromium (VI) content and vice versa (Congzheng et al., (2005).


The fatliquor NF3, found to give the lowest Cr VI content in the leather, resulted in 14.16 mg Cr VI/kg. This level was only lowered to 10.83 after 2 weeks at 100% humidity and increased to 66.25 at 12% humidity. The high Cr VI contents in leathers stored at low humidity show the possibility of Cr VI formation in just 2 weeks storage. The study and findings were impractical and leather stored at high humidity would require fungicides, which may also cause allergies.

There is not yet a proven, acceptable method to control Cr VI formation during storage, transport and ageing of leathers, manufacture of footwear and ageing and use of manufactured products. Any chrome tanned product, whether produced in Europe or elsewhere, could generate Cr VI during storage and wear, even after an antioxidant treatment.


  • The proposed restriction on Cr VI should not be introduced.
  • Better management of chrome allergies to leather items should be investigated.
  • Cr III and Cr VI are both capable of eliciting dermatitis at low concentrations.
  • It has not been demonstrated that the restriction will reduce chromium sensitivity to leather items: an important study found that 30% of chrome-allergic patients reacted to leathers, which contained less than 3mg Cr VI/kg.
  • Control of Cr VI formation in finished leather is an unsolved problem and there is no viable substitute for chrome containing shoe leathers.
  • The range of consequences of the restriction throughout the global leather industry must be considered.


Congzheng Y, Pengjie L, Genxing S, Liming D, Huijun R. (2005). The influence of relative humidity on the level of Cr(VI) in chrome-tanned leather. J Soc. Leather Technol. Chem.; 89:194-198.

ECHA Annex XV Report, Proposal For A Restriction: Chromium (VI) compounds 2012


Hansen MB, Johansen JD, Menné T. (2003) Chromium allergy: significance of both Cr(III) and Cr(VI). Contact Dermatitis; 49(4):206-12.

2006 a) Hansen MB, Menné T, Johansen JD. (2006). Cr(III) and Cr(VI) in leather and elicitation of eczema. Contact Dermatitis; 54(5):278-282.

2006 b) Hansen MB, Menné T, Johansen JD. (2006). Cr(III) reactivity and foot dermatitis in Cr(VI) positive patients. Contact Dermatitis; 54(3):140-144.

Warshaw EM, Schram SE, Belsito DV, DeLeo VA, Fowler JF Jr, Maibach HI, Marks JG Jr, Mathias CG, Pratt MD, Rietschel RL, Sasseville D, Storrs FJ, Taylor JS, Zug KA, (2007). Shoe allergens: retrospective analysis of cross-sectional data from the North American contact dermatitis group, 2001-2004. Dermatitis; 18(4):191-202.

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