Testing for nickel in footwear and leathergoods

How EN 1811:2011 impacts on users of nickel components.

by Martin Heels

Unlike the majority of substances that are restricted by European, US or Asian legislation, nickel does not detrimentally affect the environment or cause severe reactions in the majority of the human population. It is a silvery-white metal used in electroplating and batteries, and is a constituent in some metal alloys which can be cast into many different shapes. This is why nickel also might be present in metallic footwear trims, zips, buckles and eyelets.

Although there are serious health risks if nickel is inhaled or ingested, it is not classified as a carcinogen or as an irritant. Despite this, nickel is, in fact, an allergen that can cause skin irritation and skin sensitisation, with approximately 10 per cent of the population thought to be affected by a nickel allergy. This can be evident as dry itchy skin, or redness of the skin (contact dermatitis), although in extreme cases, blisters and cracking of the skin can occur which could lead to skin infections. It is due to these allergic reactions that nickel release from metal items intended to be in contact with the skin is restricted within Europe, as entry 27 in REACH – Regulation (EC) number 1907/2006 Annex XVII.

Type I and type IV allergen

It has been reported that nickel is the most frequent cause of contact allergy in Europe. Nickel is generally a type IV allergen, meaning that if an individual’s skin comes into contact with nickel, it may not give rise to an immediate reaction; the skin dermatitis might not appear until several days after exposure. On rare occasions, nickel can give a type I reaction, in which immediate symptoms appear. If contact with nickel does cause contact dermatitis, future exposure can give rise to a similar reaction. This is even the case if the exposure is much less than before, because the skin becomes increasingly sensitive to nickel (hence, the metal is termed a ‘skin sensitiser’).

Legislation

The original European Nickel Directive (94/27/EEC) became enforceable in 2000 and was amended in 2005 (2004/96/EC). These 2005 requirements were subsequently incorporated into REACH – Regulation (EC) number 1907/2006 Annex XVII as entry 27, where they have been part of a European regulation since June 2007. Manufacturers, importers, sourcing companies or retailers cannot place on the market articles within the EU that are intended to come into direct contact with the skin – such as buttons, buckles and zips – and which can release nickel at a rate greater than 0.5µg/cm²/week.

The units used to measure nickel release are unusual because the testing protocol requires items to be extracted in a synthetic perspiration solution for seven days before the concentration of nickel in the extraction solution is determined. It is important to note that the use of nickel in such items is not banned, as long as the nickel migration is lower than this maximum rate.

Assessing items against the legislation

Metal items, such as buckles and zips used in footwear, garments and handbags, may contain nickel in their surface coating, but it may also be present in the core material beneath the surface. Assessing nickel release from surface coatings is straightforward, as testing is carried out on the received sample. However, testing the core material is more complex, as it involves a procedure designed to simulate two years’ wear, thereby slightly damaging the surface and exposing layers beneath the coating. The procedure is documented in the testing standard EN 12472. The original 1998 version of EN 12472 was revised in 2005, and the wear medium and testing apparatus were changed significantly.

Nickel release testing

After this procedure, the extraction in artificial perspiration solution is carried out in accordance with EN 1811:2011 + A1:2015. The specimen is immersed in the artificial perspiration solution and maintained at 30°C for seven days. Testing is currently carried out in accordance with the 2011 + A1:2015 version of this standard. There are many significant changes from the previous 1998 version, which was withdrawn in March 2013.

One of the most important differences is that the adjustment factor has been removed. In the final calculation, the result was multiplied by an adjustment factor of 0.1 before the final result was reported. Although members of staff receiving or reviewing test reports may never have been aware of this factor, the 2011 test method does not include an adjustment factor. The consequence of this means that samples assessed under the 1998 method will give a much higher result when assessed to the current standard.

In addition, uncertainty of measurement has been incorporated when comparing the result to the REACH Annex XVII entry number 23 requirement. The introduction of this very complex subject means that an article is non-compliant only when the nickel release is greater than 0.88mg/cm²/week. This is due to the combined measurement uncertainty of 46 per cent resulting in a fail only when the test result is greater than 0.5mg/cm²/week plus uncertainty.

Publishing Data

This article was originally published on page 46 of the January 2019 issue of SATRA Bulletin.

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