Chrome VI is a kind of poison harmful to human and environment. It is easily absorbed by human through assimilation, respiratory tract, skin and mucosa. It will lead to raucity, nasal mucosa atrophy, especially perforation of nasal septum and bronchiectasis by air, disgorge and stomachache by assimilation, peltry and eczema by skin. The most serious damage is carcinogenesis .
Cr plays an important role in tanning leather, and makes it flexible. In electricity, metal processing, electroplating industries, the solvent contains Cr(Ⅵ). The residual Cr(Ⅵ) in leather will be absorbed by skin and respiratory tract, and damage to stomach, liver, kidney, and eyes, retinal hemorrhage and optic atrophy appearing.
Chrome tanned leather is an extremely useful and valuable commodity for most industries because of its flexibility. The naturally occurring chrome III, which is used as the tanning agent, is perfectly safe if the leather is produced under the correct conditions and must not be confused with chrome VI. There are many advantages of using chrome tanned leather and this is why it is preferred for most leather products.
In leather production there are three ways in which chrome III could oxidise into chrome VI:
During the tanning process –If the temperature or pH is too high then chrome III has the propensity to oxidise to chrome VI.
Chemicals used –If chrome powder is sourced from a non-reputable supply then there is a possibility that it may contain chrome VI.
Finished leather –After the leather has been made, there is a small chance of chrome III oxidising into chrome VI at high temperatures. This is why chrome tanned leather should never be incinerated.
The test method to detect chrome VI has recently been revised and published as EN ISO 17075:2007. This method has a detection limit of 3ppm and for a leather to pass; chrome VI must be none detected.
What is chrome VI?
Hexavalent chromium VI is the hazardous form of the naturally occurring chromium element and the safe trivalent form of chromium used in tanning. Chromium III tanned leather can form traces of chromium VI under certain environmental conditions. The conversion from Chromium III to Chromium VI is an oxidation process and can be facilitated by the factors like heat, UV radiation, changes in pH, presence of unsaturated organic compounds (e.g. natural fats), oxidizing agents and many other factors. Often several of these factors need to be present at the same time.
The formation of Chromium VI from Chromium III can be slow which means that articles not containing Chromium VI directly after production of the leather may develop some Chromium VI during transport and storage, especially where there is a propensity for chrome VI to form due to the conditions outlined.
Under well managed production conditions, chrome tanned leather should pose a very low risk of containing chrome VI. Poor process control, poor quality chrome powder and adverse storage conditions can however, cause the formation of the harmful hexavalent form of chromium.
The risks
Chrome VI is recognized as a human carcinogen when it is inhaled. Chronic inhalation of chrome VI has been shown to increase risk of lung cancer and may also damage the small capillaries in kidneys and intestines.
Why carry out chrome VI testing?
The new legislation on chrome VI will come into force on May 1st 2015; the forthcoming restriction will state that leather articles and articles containing leather parts that come into contact with the skin cannot contain 3 mg/kg or more of chromium VI by weight of the total dry weight of that leather part. This means all such articles that come into contact with the skin are within the scope, regardless of the length of time of the contact.
Examples of products that are within the restriction scope include:
Footwear
Gloves
Clothing
Accessories e.g. hats
Belts and braces
Watch straps
Purses and wallets
Bags
Horse riding gear
Dog leashes
Automotive seats
Covers for car steering wheels
Furniture
Chromium remains a vitally important chemical in the global production of leather with at least 80% of global leather production being tanned with chromium III salts. It is a highly effective tanning agent producing leather with a flexible range of properties making it suitable for many end uses.
The imminent EU wide restriction on chrome VI, which will amend Annex XVII the REACH Regulation, will expand the existing restriction on chromium VI compounds.
This proposed restriction began in September 2011 whenDenmarknotified the European Chemicals Agency of its intention to submit a formal proposal to restrict chromium VI in leather articles.
Following notification of acceptance from the European Commission the forthcoming restriction will state that leather articles and articles containing leather parts that come into contact with the skin cannot contain 3 mg/kg or more of chromium VI by weight of the total dry weight of that leather part. This means all such articles that come into contact with the skin are within the scope, regardless of the length of time of the contact. Examples of products that are within the restriction scope include: footwear, gloves, articles of clothing, accessories such as hats, belts and braces, watch straps, purses and wallets, bags, horse riding gear, dog leashes, auto seats, covers for car steering wheels, and furniture.
The restriction, which is expected to come into force in the first quarter of 2015, recommends that EN ISO 17075, which is currently the only internationally recognised analytical method available to detect chromium VI in leather, is used. The limit of the proposed restriction is based on the detection limit of this method, which is 3 mg/kg.
Where can Chrome VI be found and why is it present?
Chromium III tanning products are widely used and are not toxic.
However, chromium III tanned leather can form traces of chromium VI under certain environmental conditions. The conversion from chromium III to chromium VI is an oxidation process and can be facilitated by the factors like heat, UV radiation, changes in pH, presence of unsaturated organic compounds (e.g. natural fats), oxidizing agents and many other factors. Often several of these factors need to be present at the same time. Best available technologies and good manufacturing practices can minimize the risk of chrome VI formation.
The formation of chromium VI from chromium III can be slow which means that articles not containing chromium VI directly after production of the leather may develop some chromium VI during transport and storage.
Challenges for Industry
With the impending restriction of Chrome VI, it appears that authorities have ramped up the pressure in relation to compliance. Recently, there has been an overwhelming increase of chrome VI notifications in the weekly RAPEX reports. A wide range of products containing chrome VI in excess of 3mg/kg are constantly being withdrawn from the market, recalled from end users and rejected at the border, impacting manufacturers and retailers in terms of cost and reputation.
What can you do?
Chrome VI formation can be avoided by using correct procedures and having a good understanding of the chemistry involved. Key steps should be followed in order to gain the highest level of assurance that leathers will not contain chrome VI. These factors include chemical purchasing, controlling pH levels, addition of propriety chemicals etc.
PTS Testing Service have extensive experience with regards to chrome VI. We offer chemical testing for chrome VI as well as technical support, tannery audits and consultancy services.