Meeting mercury limits

An awareness of restricted substances is becoming more important for all involved in the leather industry. Many substances are restricted either through legislation or eco-labels or more commonly by major global brands. Although the leather industry is becoming more aware of the substances that are restricted, it is of
interest to consider the background to their listing, and some of the reasons behind their restriction.

Naturally occurring
Mercury occurs naturally,
mostly in the form of sulphides of the compound, and the most widespread accessible source is cinnabar. Metallic mercury is obtained by heating cinnabar in air and condensing the vapour. Metallic mercury is slightly toxic, but salts and compounds of mercury are highly toxic. Organic compounds are more toxic than inorganic compounds. The most well known, highly toxic example being methyl mercury.

Mercury can occur in a variety of forms such as:
•    elemental mercury
•    the mercury (II) cation
(dissolved in rainwater, or as the ore cinnabar, HgS)
•    organometallic compounds such as methyl mercury and dimethyl mercury
Industrial uses
Mercury is used in a number of industrial applications, in the electrical industry and in the medical professions. The form in which mercury is used (whether as elemental mercury or as a compound) is dependant upon the industrial process. Mercury thermometers and dental
amalgams are medical applications that many people will be aware of. There is concern over dental amalgams and this relates to the evaporation of elemental mercury.
Non-medical uses of mercury include its presence in a variety of products: cleaning solutions, preservatives, paints, and anti-fouling agents for wood and other surfaces. In addition to the release of mercury to the environment as a result of the manufacture or use and disposal of these products, mercury contamination of the environment will also occur in high concentrations in the areas where cinnabar is mined.

Environmental impact
Mercury can enter the environment in a number of other ways, not only as a result of human activity. Volcanic sources, for example, emit an estimated global total of 60,000 kg of mercury per year. This is twice the estimated human release of 30,000 kg of mercury, which comes from the combustion of fossil fuels and other forms of incineration as well as other industrial emissions related to the use or manufacture of mercury or mercuric materials.
Sediments near pulp and paper works, for example, are known to contain high levels of mercury if the paper has been bleached with chlorine or sodium hydroxide (elemental mercury is employed in the manufacture of these bleaching chemicals). Biomass accumulates mercury and forest fires can also be a source of mercury release to the atmosphere. Sea water contains mercury in both the elemental form and in the ionic form. There is some evaporation of elemental mercury from the surface of the sea.

The importance to the leather industry
Mercury can be found within the leather supply chain. Organo-mercury compounds can be used as microbiocides. There may also be the potential for contamination from both mercury and other heavy metals with poor quality chemicals such as chrome powder. In addition, mercury can be present in pigments and dyes used for the finishing of leather and, due to the fact that mercury is an omnipresent element, it is conceivable that it could be detected in leather even with a clean chemical supply chain as the limits are further lowered.
One legislative area with potential impact on the leather industry is the inclusion of mercury in the substances restricted by the EU Safety in Toys regulations and EN71-3. This restricts the extractable levels to 60ppm potentially in child appealing products. Mercury is also listed in the new RoHS directive, which restricts its presence (along with other substances) in electrical equipment which will include leather watch straps as a component of a watch.
In addition to the legislative issues, there are several Eco-labels and brand specifications that limit the presence of mercury in leather and textiles. These have strict limits which are typically set at 0.02ppm (20μg of mercury per kg of leather) of extractable mercury (using an acidic perspiration solution). These can be extremely challenging for a leather supplier to meet especially if mercury is in the
supply chain in terms of chemical contamination.

Summary
In summary, mercury is increasingly becoming a focus in terms of both legislation and global brands. It is found in the leather supply chain and BLC can help with both testing, supply chain management and chemical cleansing.
For further information contact info@blcleathertech.com